Veterinary Necropsy Procedures-Cabana

Veterinary Necropsy Procedures EM Cabana, DVSM, MVSt Professor, Veterinary Pathology College of Veterinary Science & Medicine Central Luzon State University Science City of Muñoz, Nueva Ecija Philippines

All Rights Reserved  2008 First Published 2001 by the CLSU Alumni Association, Inc.

No part of the contents of this book may be reproduced or transmitted in any form or by any means without written permission from the author or publisher

Foreword While conducting the lectures for undergraduate students in general veterinary pathology, my students and I noted the dearth of literatures dealing with procedures in performing necropsies. It appeared that similar to most skills that were transferred from generation to generation of veterinarians, necropsy techniques considerably varies, yet the object of the exercise remains the same, i.e., to systematically examine the animal carcass. While doing my postgraduate degree, I was tempted to ask my former professors an appropriate text for me to master the skills. They replied that there seems to be no one documenting the procedure prompted me to write one. This book therefore is an attempt to document the procedures. While I do not purport to be the original source of the routine necropsy techniques herein described, I attempted to include techniques for cosmetic necropsies. It happened to me one day that I was awestruck by the owner holding her dead pet and asking me if there was an alternative procedure that will not “mutilate” her pet dog. I get hold of her dead pet and made a deal that a cosmetic procedure will be done. My academic supervisor, seeing the results then told me to “better document that one too”. It is hoped that this book will be of value to both students and practicing veterinarians alike. The initiation to veterinary pathology seems to start at the necropsy rounds. Have our predecessors did not study the changes in organs and tissues through skillful necropsies, then I surmise that our knowledge about animal diseases could have been very, very limited indeed. Let the initiation then begin! EM Cabana June 2001

Table of Contents Chapter 1 – Necropsy: An Introduction General Principles The Necropsy Record Describing Lesions Collection and submission of Specimens

1 1 5 10 11

Chapter 2 – Tissue Changes Normal Anatomical Structures Physiological Changes Senile Changes Agonal Changes Post Mortem Changes Factors influencing Rate of PM Autolysis Terms used to describe PM Changes PM Changes on Organs & Tissues

12 12 14 16 16 17 17 18 19

Chapter 3 – Routine Necropsy Dissection Stage Display Stage Examination Stage

22 22 25 26

Chapter 4 – Cosmetic Necropsy Preliminaries Necropsy Procedures

35 35 36

Chapter 5 – Avian Necropsy Physical examination Euthanasia Opening the Body Cavities Examination Stage

39 40 40 41 43

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Chapter

Necropsy: An introduction

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ecropsy may be defined as the systematic examination of an animal carcass aimed to search for lesions. It is an important diagnostic tool and supports other procedures performed in the diagnosis of disease cases in a herd or flock. The necropsy procedure employed by veterinary students and practitioner alike varies from examiner to examiner and from specimen to specimen. The conduct of a particular routine depends largely on the individual preferences of the examiner, the availability of the materials and equipment for the examination, the condition or state of the carcass, the extent of the examination required, and the mode of examination requested by the client or owner. It is often observed that necropsy done by the uninitiated or the untrained is characterized not by the voluminous information gathered that have little importance to the diagnosis of a particular case in question. It is the absence of information vital to the formulation of a diagnosis. Ill-performed necropsy thus confuses the understanding of a disease process. A working routine is desirable so that adequate information is gathered that will aid in the formulation of a diagnosis. One factor to consider in the formulation of a diagnosis is the accuracy of the data gathered. A systematic approach in necropsy is required to so that appropriate and adequate information be gathered during the examination. This manual will describe the standard procedures for the necropsy examination of domestic animals adaptable to most laboratories and in field conditions. It is hoped that it will help practicing veterinarians and students alike to adapt a working routine in performing necropsy.

GENERAL PRINCIPLES IMPORTANCE OF NECROPSY The examination of dead or terminally ill animals offers opportunities in studying the processes involved in disease situations. Various medical imaging techniques have evolved in recent years providing adequate information on the morphologic alterations of organs and tissues following disease. However, necropsy still provides a first hand look on what really happened along the course of the disease. In poorly understood disease situations, tissue alterations resulting from or as a reaction to the disease process may or may not be detected during clinical examination. Results of clinical

examination alone may not be sufficient to define the process involved. Thus, gross and microscopic examination of diseased organs and tissues may lend valuable information in understanding the pathogenesis of a disease. Morphological changes when correctly recorded and interpreted provide a basis for correlating functional changes seen in a particular disease process. Not all disease processes will show dramatic morphologic alterations in organs and tissues. Some clues may be derived however from necropsy examination that will provide valuable information in the recognition of such functional disturbances. The challenge is on the examiner to recognize these clues. While most students and veterinary practitioners would regard necropsy as purely of academic interest, the purpose of necropsy does not end on the recognition of the lesions alone. Skillfully performed necropsy with all the information gathered, accurately recorded and interpreted will provide valuable assistance in the formulation of animal health and production strategies aimed to prevent and control animal diseases in a herd or flock. The primary aims of necropsy are to uncover the cause of death of an animal by defining possible etiology and pathogenesis to arrive at a diagnosis. Yet, the usefulness of necropsy resides on the application of the information gathered in the formulation of appropriate treatment, control and disease prevention measures.

TIME FOR NECROPSY The best time for necropsy is immediately after death of an animal. This is because post mortem processes of decomposition (autolysis) follow at a fairly rapid rate that obscures subtle changes in organs and tissues. Also, post mortem invasion of the organs and tissues by normal microbial flora of the gut may make the isolation of the causative agent in question with difficulty or even impossible, especially in suspected bacterial infections. If histopathological examination of the diseased organs and tissues is anticipated, it is best to examine the cadaver immediately and collect the required specimens the soonest possible time. This is particularly true if histopathological examination of the gastrointestinal tract is required. Its content of microorganisms, enzymes and digesta make its decomposition more rapid than the other parts of the animal cadaver. Thus, if examination of the gastrointestinal tract is anticipated, it is recommended to euthanase the moribund animal. Do the examination right away, than wait until the animal dies and miss and opportunity to have it examined in its fresh state. Cool the cadaver rapidly in a refrigerator or freezer if it is not feasible to examine the animal immediately after death due to some constraints. This is done to delay the process of post mortem decomposition. For specimens submitted during off2

hours or during weekends, cut open the abdomen and remove the viscera, particularly the segments of the gastrointestinal tract and examine the parts right away. The other parts of the cadaver may then be saved in a refrigerator and examined the next instance or day, although some degree of post mortem changes must be anticipated. If necropsy will be delayed for some reason or another (example the cadaver will be shipped to a distant laboratory and will take considerable time before it reaches its destination), freeze the whole cadaver solid. Pack it in dry ice before shipping, observing the pertinent rules and regulation in the transport of suspected biological hazards. Never pack the cadaver with ordinary ice if it is anticipated that the specimen may not reach the laboratory within one or two hours. Even then, the whole specimen should be packed in a plastic bag and put enough ice packs above and below the cadaver in a Styrofoam container. Send the cadaver the soonest possible time, with the necessary information as will described later.

PLACE FOR NECROPSY There are several requirements in the selection of the place for necropsy. The place should have adequate light, water, ventilation, drainage, provisions for cadaver disposal, and provisions in lowering the chances of contaminating the surroundings. Animals that died of suspected transmissible, zoonotic or exotic diseases require that the examination be done in a laboratory. Usually, a clinical diagnosis will aid in deciding the site for necropsy; for example, a clinical diagnosis of Anthrax does not warrant necropsy at all for the potential of contamination is great. Exercise extreme care in selecting possible sites for necropsy, especially in the field. The selected site should be away from sources of feed, forage and water for the rest of the herd or flock. Avoid those sites that will be frequented by other animals in the herd in gaining access to other places. Insects, predators and other biological vectors of diseases should be warded off from the examination site.

DISPOSAL OF THE CARCASS In the disposal of the animal cadaver after examination, incineration is still the best method for the disposal of small animal cadaver. Practical reason dictates that this procedure may not be suitable for large animals. The amount of time involved in the incineration and the amount of fuel required turning the large heap of flesh and bones into ash preclude this procedure. For both small and large animals, burying deep into the ground may be practical. However, the pit should be dug deep enough so that astray animals and other predators cannot have easy access to the disposed cadaver. Also, consider the chances of contaminating the surrounding and the odor that may emanate from it should the pit be not deep and large enough to fully hold and cover the whole carcass. Exercise caution in selecting the site for the pit. The site should not be away from sources of feed or where underground water is being 3

pumped. All dead animal cadavers should be considered possible sources of contamination that should be disposed responsibly.

BASIC EQUIPMENT The choice of equipment for necropsy depends on the size of the animal, the type of examination requested (whether routine or cosmetic necropsy), and the individual preferences of the examiner. For most purposes, two sharp knives, a pair of scissors and forceps, a metal probe, and an ordinary mechanic hacksaw will be sufficient. Preferences for the size of the knives depend on the size of the cadaver, ease of handling and safety. A steel rod or sharpening stone to keep the knives sharp is essential. The forceps could be a lockable scissors type or a lifting forceps with rattoothed or serrated tips that grasp tissues without slipping. A mechanic hacksaw will prove useful for cutting bones and other hard structures. A metal probe made of stainless steel, copper or bronze, or an ordinary galvanized iron wire gauge 12 and about 10-12 inches long is useful in probing connections and patency of openings. Other useful equipment includes a small axe, mallet and chisel (for cutting bones especially in large animal cadaver), and an ordinary pruning shears (instead of a costotome) for cutting the rib cage, mandibular symphysis, and pelvic bones. Other tools or instruments may be included, as they prove useful and saves manual labor during the examination. Weighing scales and measuring instruments like a millimeter rule and graduated cylinders or measuring cups are essential for accurately recording dimensions and volumes. Two specimen bottles, one half-filled with 10% neutral buffered formalin are required for containing samples of tissues and body fluids for laboratory examination. Sterile swabs and petri dishes for the collection of samples for microbiological examination (if required) should be made available. Other materials that may be needed include disposable syringes and needles, glass slides, and ordinary fishing twine or thread for tying up hollow organs.

PROTECTIVE CLOTHING The wearing of protective clothing is not meant to prevent soiling and/or preserve the appearance of what is worn by the examiner underneath. It should protect the examiner from contamination with blood, tissues and body fluids from the cadaver that are potential carrier of infectious particles. The recommended protective clothing should provide comfort to the examiner while not compromising protection from possible contamination. The wearing of cotton coverall, rubber boots, gloves, and butcher's plastic vest is recommended and provide ample protection from contamination. These articles must be washed clean and disinfected after each use. The common laboratory gown may be used. However, the hanging flaps may easily soak with the cadaver's blood and body fluids with the examiner not noticing it, 4

and thus exposing the examiner to contaminants. Although lacking any protective clothing, the laboratory gown will be sufficient. A pair of ordinary garden latex gloves of appropriate size is useful for necropsy. Compared with the surgeon's latex glove, the latter are less expensive, more durable and provide equal protection. Necropsy without wearing any gloves is an open invitation for contamination. The gloves should fit the hands and fingers of the examiner without interfering with manual dexterity and causing numbness. Loose, also very tight fitting gloves may cause undue interference in handling organs and tissues, not to mention the awkward look and the uncomfortable feeling it may render to the examiner.

THE NECROPSY RECORD FORMS The style and type of necropsy report forms vary from laboratories to laboratories depending on the mode of document storage and retrieval system in use. The current trend in computerized data storage and retrieval most often uses forms structured to suit the particular software or database program being used. Yet, the structured entries no matter how the data are processed and stored essentially contain the basic items that include the following: 1) Case Identification - includes the assigned case number, the case code (example degenerative condition, bacterial disease, viral disease, etc.), and the date of submission and examination; 2) Owner's Identification - includes the name, address, and phone number of the owner. 3) Specimen Identification - includes the species, breed, age, weight, sex, coat color, animal number/name, and animal classification (example breeder, draft, pet, etc.), and identifying markings (example: brands, cowlicks, earnotch number). 4) Clinical History - includes the details of clinical findings, signs and symptoms observed, clinical diagnosis, the referring veterinarian's name and address, and the type of necropsy requested (routine or cosmetic necropsy); It shall also include among other the number of dead and affected animals in the herd or flock. Describe the manner of spread of the disease in the herd or flock, and the type and standard of husbandry before and after such a condition was noted. Include also the date of first cases and subsequent losses, and prior treatment given to the animal; 5) Necropsy Findings - includes the results of the necropsy examination that may be arranged by organs/system or by the sequence of examination; 6) Results of Laboratory Examination - includes the samples collected during necropsy and the results of the examination done; 7) Diagnosis - the outcome of the examination; 5

8) Examiner's Information - includes the name, qualifications and signature of the one who did the examination and formulated the diagnosis.

RECORDING INFORMATION During necropsy, it is best to record all findings as the examination progresses. Yet, thorough examination of the animal cadaver will consume a considerable amount of time. An assistant that will record the findings as the examination progresses may not be always present. Thus, it is recommended that the findings be recorded immediately after the examination and before the cadaver is disposed. If an organ or systems have been inadvertently missed during the examination, or the examiner for one reason of another forgot some details of the lesions, the specimen may still be available for reexamination. In the laboratory, the use of a tape recording unit is ideal if many specimens will be examined in a single day. This unit is practical for a busy laboratory with large necropsy specimen accession. Models of tape recording units that are particularly suitable include those with a microphone that can be pinned to the lapel and with either a foot switch or a wireless microphone, or that of a voice-activated recording unit. Although this will involve additional investment, the accuracy in recording information may far outweigh the cost should necropsy accession be large enough. It is recommended to take at least a photograph of the animal and/or lesions noted in cases where legal proceedings are anticipated. In these cases, carefully record the location and appearance of identifying markings of the animal such brands, cowlicks, and ear notches. These data are particularly sought in establishing the identity of the animal particularly in insurance claims.

PREPARATION OF THE REPORT Relevant sections of the necropsy document dealing with the case identification, specimen identification, owner's identification, and clinical history should be filled with the required information before necropsy. This may be done when the specimen is received for examination. Without these data, particularly the clinical history of the case, the search for lesions would be particularly tedious. It may even result to undue trouble to the examiner in terms of the danger posed by examining a specimen where necropsy should not be done at all (example: cases of anthrax). The general rule in making a necropsy report is to be objective in interpreting lesions, with the finished report being descriptive. The common fault in recording necropsy findings is the tendency of the examiner to interpret the lesions observed, than describing the changes seen. This may be condoned if the one who examined the specimen will also be the one who shall formulate the diagnosis. Even then, this will limit the usefulness and of the finished report, for necropsy findings are subject to 6

many interpretations and that one examiner may or may not agree with the interpretation of another examiner. This is particularly true if another person other than the one who examined the specimen will synthesize the findings and formulate the diagnosis. The finished report should be descriptive enough allowing other to clearly visualize what were observed during the examination to enable them to make their own interpretation and possible diagnosis.

DESCRIBING LESIONS Recognition of lesions requires a sound background in anatomy and pathology. Veterinary students should be aware of the appearance of normal structures and the species difference within and between species. However, as one gain experience in examining various animal species, recognition of the normal structures and what form an abnormality in the structure (or the lesion) becomes routine. Students of necropsy may find it useful to pay a visit to the local abattoir to observe the appearance of organs and tissues of domestic animal species. However, one must be aware that specimens submitted for necropsy most often shows post mortem changes that may mask or alter the appearance of otherwise normal structures. The recognition of these changes requires knowledge of pathology and considerable experience. It is not uncommon for students and the uninitiated to have a problem in describing lesions. Although veterinary pathology is rich in descriptive terms that describe the forms and appearance of any given lesion, the use of adjectives from ordinary conversational language is desirable than having no descriptions at all. It is recommended to write plainly in the report that no remarkable alterations were noted in the organ/tissue examined should that be the case, than leaving it not mentioned in the report. Also, include in the report the organs not examined for one reason or another. For most purposes, the description of any given lesion should include the following information: A. Solid organs: 1) Organs/tissue involved 2) Position, relations, and involvement of adjacent structures; 3) Size and shape; 4) Weight; 5) Color (shade, tint, hues); 6) Appearance; 7) Consistency; 8) Texture or intact and cut surface; 9) Odor; B. Hollow Organs: 1) Organs involved 2) Appearance; 7

3) Texture of intact and opened surfaces; 4) Contents, which should be qualified as to: a) Nature b) Volume/Amount c) Consistency d) Transparency e) Colour; f) Odour; In describing lesions, it is best to keep the descriptions in as few but very descriptive words as possible. Refrain from using verbose descriptions that tend to distract attention and present no clear meaning. Weights and measure should be recorded using the metric system of notation. The approximation of the weights and measure is desirable than comparing what was observed to common or ordinary articles. For example, it is far better to approximate the size of a tumor as "about 4-5 centimeter in diameter" than recording it as "about the size of a 25-cent coin in diameter." Although the latter may be considered more acceptable than having no description at all, its use in the necropsy report should be avoided.

COLLECTION AND SUBMISSION OF SPECIMENS FOR LABORATORY EXAMINATION SPECIMEN SUBMISSION Necropsy lends support to other ancillary laboratory diagnostic procedures, and those specimens for laboratory examination may be routinely collected as the examination progresses. Different laboratories have different requirements on the type of specimen required and the modes of specimen preparation and preservation. Contact the laboratory where the specimen will be sent to ensure that appropriate and adequate samples are taken during the necropsy examination. The specimen collected should be appropriately labeled for proper identification. Information required for the identification of the specimen intended for submission include the following: 1) 2) 3) 4)

The species identification The details of clinical history The relevant necropsy findings Nature of the sample collected and the mode employed in the collection and preservation 5) The form or type of examination that is requested

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It is the responsibility of the examiner to notify relevant government offices in cases where the specimen is collected from suspected cases of highly contagious, zoonotic or exotic disease. Adequately label specimens taken from such cases to warn others about the potential of spreading the infection or pose danger to the biological system, or to the courier of the specimen should improper handling occur. The full descriptions of the methods employed in specimen collection and preservation are beyond the scope of this work, and the readers are referred to the appropriate text in clinical pathology. However, a short guide will be discussed in the proceeding section.

Submission for Histopathological Examination Routinely fix specimens intended for histopathological examinations in 10% neutral buffered formalin. The pieces of organs and tissues should be collected the soonest possible time, and should not be more than 0.5 cm thick. Collect the tissue block using a sharp knife or a razor blade, exercising care not to crush or allow the tissue blocks to dry. Crushing the specimen or allowing it to dry will cause undue distortions on the morphology of cells and tissues. Moreover, the tissue block should be selected and should include both the normal and abnormal portion of the organ or tissue. Fix the collected tissue blocks immediately in 10 times the tissue volume of 10% neutral buffered formalin. Wash the specimen in physiological saline solution before fixing it in formalin if it is heavily soiled with debris. Fix specimens of the brain by cumulating the carotid artery and pumping the formalin until what flows in the jugular vein and the carotid artery at the other side is clear of blood. Alternatively, the whole brain may be immersed in a large volume of the fixative. Allow it to harden for 24 hours, and then slice the brain and take the desired sections. Segments of the gastrointestinal tract should be taken the soonest possible time and immediately after opening the cadaver to minimize post mortem changes. Cut open the segment of the gastrointestinal tract longitudinally before putting the segment in the fixative to ensure adequate and prompt preservation of the mussel lining, and to increase the surface area for the penetration of the fixative.

Submission for Microbiological Examination Collect specimens intended for microbiological examination aseptically. It is recommended to sear the surface of the organ or tissue with a hot spatula, then incise and collect the required material from the deeper portion of solid organs, abscess, or coagulated masses. From this incision, sterile swabs, tissue fragments, and aspirates may then be taken. Place sterile swabs and aspirates in a special transport media, especially if the suspect organism is a fastidious one. The choice of transport media depends largely on the microorganism suspected to be present in the specimen. Should sterile swabs be required to be taken from body cavities or openings, the swabs should be taken immediately before fully opening such part of the animal 9

cadaver. Hollow organs such as segments of the gastrointestinal tract are best handled by obtaining a loop tied at both ends and placed in a sterile petri dish.

Submission for Toxicological Examination Materials for toxicological examination should be taken free from any contaminating chemicals being used during necropsy. Chemicals that may contaminate the specimen include fixatives, detergents and disinfectants routinely used during necropsy. Although different toxicants require specific samples for chemical analyses, the following samples may be taken if toxicological examination is anticipated: 1) Whole blood and sera 2) Tissue blocks (about 100 grams) of both liver and kidneys 3) Urine 4) Stomach and intestinal contents

Contact the toxicology laboratory where the samples will be sent to ensure that the right specimen and amount are collected and the adequate precaution on handling and preservation is observed.

Submission for Parasitological Examination Occasionally, ectoparasites and endoparasites are collected during necropsy for identification. Collect samples of ectoparasites before the cadaver is cut open for examination. Ticks, fleas and lice should be carefully brushed off from the fur or feather and fixed in formalin. To disable these organisms, wet the fur or feather of the animal with a detergent solution. In collecting ticks, prevent the mouthparts from damage, by wiping the body part of the tick with ether. This will kill the tick and allow it to drop. Fix the collected specimens in 70% ethyl alcohol or in 10% formalin. Information about the degree of ectoparasites infestation should be provided along with the submission. Collect mange mites by scrapping the affected skin deeply, and put the scrapings in a glass slide with a drop of mineral oil. Roundworms collected from intestinal segments may be fixed in formalin immediately after collection. Allow it to relax by dipping in menthol solution or lukewarm water before fixation to prevent curling of the specimen. Tapeworm segments collected should include both mature and immature segments, with the scolex still intact. Never lift the tapeworm from its attachment for it will break the scolex. The scolex is important in species identification. Excise the part where the scolex is attached and fix them in formalin. Press specimens of cestodes between two glass slides held together by a rubber band, a piece of twine or paper clips before immersion in the fixative. For total worm count in ruminants, tie the abomasum at both 10

ends and save all its contents. Scrapping deeply the mucosa of the affected intestinal segment and examining the scrapings as a wet smear may do the diagnosis of coccidial infection in poultry.

Submission for Cytological Examination Smears from tumor tissues are prepared occasionally for cytological evaluation. It is often possible to have a diagnosis by preparing and examining smears (from cut surfaces of the tumor), and aspirates even before tissue blocks of the tumor tissues are processed by conventional paraffin embedding technique. Allow the smears to dry immediately after collection to preserve the cell architecture. Fixation may be done by heat treatment, or by dipping in absolute methanol. Some workers suggested the use of hair spray, which presumably contain alcohol in a concentration that is sufficient to fix the cells in the smears. Smears may be prepared from body fluids by putting a few drops onto the glass slide. The fluid may be collected and centrifuged and the cell pellet at the bottom of the tube fixed in formalin or methanol and the smears prepared. Alternatively, use gelatin or albumin to suspend the cell pellet and then fix the mixture in formalin. This preparation may then be submitted for routine paraffin embedding technique similar to a tissue block.

Submission of Blood and Body Fluids Blood samples should be collected prior to euthanasia of moribund animals. In some cases, blood samples may still be obtained in animals that have been dead from three to four hours. This is done by aspirating the blood contained in the heart prior to detachment and dissection of the chambers. The addition of anticoagulants (e.g., ethylenediaminetetraacetic acid or EDTA) should be considered if plasma is to be extracted. If sera are required, it is best to collect blood in a glass receptacle to promote clotting. Alternatively, glass beads may be added. The general rule in collecting body fluid is to obtain samples free from contaminants. Body fluids should be collected as the examination progresses if it is anticipated that such examination is required. Ascitic fluid should be qualified as to amount, Colour and turbidity. Aspirating directly from the urinary bladder may collect urine. Cerebrospinal fluid should be collected prior to opening the brain. This should be done by aspirating the fluid through the aid of syringe and needle at the cisterna magna.

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2

Chapter

Tissue Changes

hanges in the appearance of the structure of organs and tissues make the recognition of lesions difficult for students of necropsy. Some are considered incidental findings during necropsy. These changes may be categorized into five major groups as follows:

C

1) Normal anatomical variation 2) Physiologic changes 3) Senile changes 4) Agonal changes 5) Post mortem changes. The findings of one or more of these changes are often difficult to interpret and correlated with other tissue changes and/or lesions that may be present. It is therefore essential to recognize these changes to prevent confusion. The following lists are not meant to be comprehensive.

NORMAL ANATOMICAL STRUCTURES AND SPECIES VARIATION Veterinary students and practitioners should be aware that anatomic variations occur within and between species. The appearance of organs in one species group cannot be assumed to be similar for most species of the same group. Variations occur even within the same animal group. Following is a list of structures and other findings included under this category: 1) Mucoid material in renal pelvis of horses - this is due to the presence of mucin secreting goblet cells in the epithelia of renal pelvis and calyces. 2) Pallor of the kidney cortex in cats - this is due to the abundance of intracytoplasmic lipid in tubules of nephrons. 3) Nodules of Arantius - found at the center of the free edge of aortic and pulmonary valves of the heart in horses and pigs. 4) Valvular haematoma in atrio- ventricular valves in young ruminants - occur as blood-filled cyst on margins of the valve of the heart. 12

5) Os cordis in cattle - consist of bones embedded in the myocardium at the base of the aortic valve. 6) Unguiculate papillae - these are keratinized papillae at esophageal groove of ruminants. 7) Torus pyloricus - this is a tongue- shaped epithelium covered bulge of tissue at gastro-duodenal junction in pigs and cattle. 8) Duodenal papillae - nodules in the mucosa of the proximal duodenum and these structures are present in most species. These are the sites where the bile duct and pancreatic ducts open into the duodenum. 9) Pigmentation of mesenteric lymph nodes and the presence of haemo- lymph nodes in ruminants. 10) Melanosis of organs - gray or black pigmentation of meninges, brain, parenchyma, kidney, adrenals, uterus, lungs, esophagus, oral cavity, gastric and intestinal mucosa, and intima of great vessels of the heart in most species. 11) Os penis of dogs - consist of bone at the corpus cavernosum of the penis. 12) Absence of seminal vesicle and bulbo-urethral glands in dogs. 13) Discrete fine nodules in the pancreas of cats - these are pacinian corpuscles normally found in the pancreas of this species. 14) Presence of caseous material in the prepuce of boars. 15) Presence of whitish plaques in the esophageal mucosa of animals that have not eaten for some time. 16) Conversion of red marrow into a gelatinous mass - seen in malnourished animals and is more pronounced in ruminants. 17) Hyperplasia of lymphoid follicle with formation of prominent nodules in pharynx and larynx of young horses. 18) Dilated lymphatics in epicardial surfaces of heart in horses. 19) Cysts in kidneys of pigs - maybe solitary or multiple, and most are congenital abnormalities of no clinical significance.

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PHYSIOLOGICAL CHANGES The normal functions of the animal body usually lead to some alterations in the gross appearance of organs and tissues. This may be affected by a host of factors related to the state of nutrition, endocrine influence, circulatory status, and stage of production. Tissue changes under this category include the following: 1) Post-prandial physiologic hyperemia of stomach mucosa - occur as reddening of the stomach mucosa in most species. This change is more pronounced in the horse and pig. The visible absence of inflammatory exudates differentiates it from gastritis. 2) Copious amount of mucus in stomach mucosa in the horse and pig - this is due to continued secretion of mucus in the stomach even after a few minutes after death in these species. 3) Distended gall bladder in most species that have not eaten recently - the gall bladder contains watery-pigmented bile, and this finding is more pronounced in dogs and ruminants. 4) Pallor of the liver in pregnant and lactating animals, and this is particularly seen in ruminants. 5) Uterine mucosal changes in appearance, texture and contents - this is part of the normal cyclical activity of the uterus following pregnancy and parturition. If the animal has recently given birth, pink- colored sludge like material with no offensive odor may be seen contained in the uterus. 6) Atrophy of the prostate in male animals after castration - the prostate show great deduction in size and with shriveled connective tissue capsule. 7) Vascular congestion and hyperemia of the gastrointestinal tract - seen in animals that have taken a meal shortly before death. 8) Yellow precipitate in renal papillae of piglets, usually associated with dehydration and/or insufficient urine flow.

SENILE CHANGES Changes in the structure and appearance of organs and tissues occur as the animal matures. These changes might be confused as lesions during necropsy. Senile tissue changes seen in domestic animals include the following:

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1) Tension lipidosis in the liver - seen most commonly in cattle and horses. Focal pallor of the liver parenchyma immediately next to the mesenteric attachment characterizes this. 2) Nodules in the liver of old dogs - these nodules are of variable size, and may be deep in the parenchyma or sub capsular in location. They are composed of hyperplastic liver parenchyma. 3) Fatty cyst in old cats - these are brownish nodular masses found on the sub capsular surfaces or deep into the parenchyma of the liver. 4) Cystic hyperplasia of gall bladder mucosa in dogs - this takes the appearance of fleshy folds in the mucosa with fluid-filled cysts. 5) Nodular hyperplasia of pancreas and adrenal glands - these structures should be differentiated from neoplastic nodules. 6) Multifocal pleural fibrosis in cattle and sheep - these are observed more commonly on the diaphragmatic surfaces of caudal lobes of the lungs. 7) Focal grittiness in trachea, bronchi and lung parenchyma of old dogs and cats. 8) Anthracosis in dogs and cats - frequently seen in those animals living in the city. The lung parenchyma may show fine dark coloration. The draining lymph nodes may also show the same changes. 9) Cholesteatoma (Cholesterol granulomas) in choroid plexus in the lateral ventricle of the brain in horses - these are discrete nodular masses that may be tan, sometimes mineralized gritty nodules. These are accumulations of cholesterol and macrophages on the distal tips of the choroid plexus. 10) Medullary calcification in the kidneys of dogs and cats - occur as white gritty radial streaks in the kidney medulla. Sometimes, they appear as whitish streaks that border the cortex and the medulla. 11) Par ovarian cysts in old dogs - these may be solitary or multiple and situated on the surface of the ovary and in the adjacent mesosalpinx or mesometrium. These structures may contain colorless fluid. 12) Prostatic changes in dogs - there may be enlargement, or hyperplastic nodules may be seen. Laminated and calcified masses deep within the parenchyma may be noted.

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13) Nodular endocardiosis in dogs - these changes occur in the atrio-ventricular valves and appear as shiny nodules at the edges of the valves. They may be multiple, and their significance should be assessed in terms of their effects on the patency of the affected valve. 14) Siderotic nodules and extra splenic tissues in dogs - Siderotic plaques are hard and gritty pale to yellowish nodules seen more commonly at the edges of the spleen. Extra splenic tissues occur as nodules of varying sizes scattered at the omentum near the spleen, and may represent previous traumatic injury to the spleen. 15) Osteoarthritis in dogs - this is common in large breeds of dog, and may take the form of erosion of the articular cartilages. Other findings include thickening of the joint capsule with deformation of the articular surfaces. 16) Conversion of red marrow into fat in most species. 17) Telangiectasis of liver in old debilitated cattle. 18) Small, atrophic lymph nodes in old sheep 19) Subendocardial materialization in ventricle or atria of adult horse. 20) Haemomelasma ilei in horses - consist of elevated subserosal plaques of variable size, shape and color on the antero- mesenteric surface of distal small intestine and colon. 21) Fibrous tags attached to the liver capsule, particularly on diaphragmatic surface in horses and buffaloes.

AGONAL CHANGES Agonal changes are those tissue changes that occur immediately before death or following cessation of vital functions. While dying, some changes occur in tissues and include the following: 1) Vascular congestion of most organs - seen particularly in the lungs and pancreas. 2) Pulmonary emphysema in ruminants and pulmonary edema in dogs - the emphysema is due to labored breathing during the agonal period. The pulmonary edema is due to agonal impairment of the venous return of blood.

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3) Hemorrhages in the heart in most species - occur as streaks of hemorrhages and are more pronounced on the endocardial surfaces. 4) Adrenal congestion and hemorrhages - seen in most species and more commonly observed in cattle and horses. 5) Food materials in the lungs and airways - this is more commonly observed in ruminants and should be differentiated from ante mortem aspiration of foreign materials. 6) Congestion of the meningeal vessels in the brain of most species - may be related to redistribution of blood to vital organs.

POST MORTEM CHANGES Post mortem changes result from degradation of tissues associated with the release of proteolytic lysosomal enzymes from the cells. These processes (called post mortem autolysis) occur automatically after death of the animal. It must be remembered that autolysis also occur following death of a limited portion of an organ or tissues (necrosis). The term post mortem autolysis appropriately distinguishes the same processes that occur after death of the whole animal. Post mortem autolysis is influenced by a host of factors. It is particularly enhanced by the action of bacteria. Bacteria that form part of the microbial flora of surface mucosa particularly in the gut proliferate soon after death. This possibly occurs due to alterations in the environment, where the usual defense mechanism of the animal body ceases to operate. Also, the bacterial proliferation may be due to the availability of a large amount of growth promoting substrates. Following their proliferation, invasion of organs and tissue occurs possibly through the vessels and lymphatics. Animals that died of bacterial diseases usually show post mortem changes rapidly than those that died of other causes. FACTORS INFLUENCING THE RATE OF POST MORTEM AUTOLYSIS The factors that influence the rate of post mortem changes include the following: 1) Temperature - The mechanism of enzyme action is temperature- dependent. Ambient environmental and body temperature of the carcass accelerates post mortem autolysis. 2) Post Mortem Interval - Post mortem autolysis occur immediately after death of the animal. The degree of post mortem changes expected to be seen in an animal cadaver depend on the time elapsed before necropsy. Post mortem 17

autolysis is progressive with time, and the longer the time elapsed the greater the degree of post mortem changes in organs and tissues occur. 3) Cause and Mode of Death - Generalized infection such as septicaemic bacterial diseases hasten the appearance of post mortem changes. 4) Condition of the Animal before Death - The condition of the animal before death, particularly its nutritional status influences the rate of post mortem autolysis. Obese animals tend to show an accelerated appearance of post mortem changes. This condition is probably related to the insulating effect of the fat layer that retards cooling of the body after death. 5) Tissue-related Factors - The degrees of the expression of post mortem changes vary from tissues to tissues. The presence of bacterial flora, enzyme secretions, and the availability of moisture and substrates influences the rate of post mortem autolysis. SPECIAL TERMS USED TO DESCRIBE SPECIFIC POST MORTEM CHANGES 1) Rigor mortis - refers to the contraction and stiffening of muscles after death. Most literatures consider the fall in the availability of adenosine triphosphate (ATP) as the possible cause of terminal muscle fiber contraction after death. Other plausible explanation includes the influx of calcium ions after cessation of the sodium pump. Classically, rigor mortis begins from 1-6 hours after death and passes off in 24-48 hours. However, several factors influence the onset of rigor mortis and these include the following: a) Nutritional status of the animal b) Environmental and body temperature of the cadaver c) Cause of death Well-fed animals have large glycogen reserves, and may show a delay in the onset of rigor, while cachectic animals may develop rigor quickly. Animal cadavers that are exposed to hot temperatures may develop and passes off rigor mortis quickly. Those that died of septicaemic diseases may not develop rigor mortis at all. Once a part of the animal body that has passed into rigor is moved, that part will pass off rigor mortis. This has some significance in human medico-legal cases. 2) Algor mortis - Gradual cooling of the animal body after death, and is associated with a fall in ATP. 3) Livor mortis - The settling of blood to the down side of the animal body. Gravitational force causes this to happen. This gravitational settling of blood and 18

body fluids results to intense reddish coloration of the organs and tissues at the down side of the cadaver. 4) Hemoglobin imbibition - Pinkish to reddish coloration imparted to tissues due to the lysis of red blood cells. This is most evident on the surfaces of large arteries and in outer surfaces of visceral organs. 5) Bile imbibition - Golden yellow coloration imparted on tissues following seepage of bile. Discoloration is most evident on the surfaces of organs in contact with the gall bladder, and on duodenal mucosa. 6) Pseudomelanosis - Greenish gray to dark coloration of tissues. This is due the action of bacteria to hemoglobin forming hydrogen sulphide. Pseudomelanosis suggests a more advanced stage of post mortem degradation of tissues. 7) Chicken Fat Clot - An old term referring to the gelatinous mass formed by separation and coagulation of plasma proteins from the component of blood. This is usually seen inside the major blood vessels and the heart. They sometimes give a cast of the ramifications of the vessels. To prevent misconceptions, the use of this term should be avoided. 8) Currant Jelly Clot - An old term applied to coagulated blood. The term becomes obsolete and should be avoided.

COMMENTS ON SPECIFIC POST MORTEM CHANGES IN VARIOUS ORGANS AND TISSUES Gastrointestinal Tract Segments of the gastrointestinal tract undergo rapid post mortem changes. This is due to the presence of digestive juices, bacterial flora, and substrates needed for the growth of microorganisms. Immediately after death, contractions of the villi occur and result to sloughing of the intestinal epithelia. Grossly, a mucoid whitish sludge may be observed, and this may be stained yellow with bile. As time progresses, gaseous distensions occur. This invariably results to stripping of the mucosa, perforation and rupture. Occasionally, stagnant blood may be lysed and impart a reddish coloration to the contents. Hemoglobin imbibition may impart a reddish color to the serosa. In ruminants, sloughing of the epithelia of the forestomach occurs.

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The Liver and Gall Bladder Hemoglobin imbibition imparts a shiny reddish discoloration on the surface of the liver. The liver parenchyma close to the gall bladder may be stained yellowish or greenish because of bile imbibition. As time progresses, the liver may loss its turgidity, become soft and clay-like in color and consistency. The presence of gas-distended bubbles on the parenchyma usually suggests a more advanced stage of post mortem decomposition. The gall bladder mucosa easily detaches after death.

The Pancreas Post mortem change occur rapidly in the pancreas. It may be discolored red from hemoglobin imbibition, lose its lobular pattern, and become soft and translucent. The portion that is facing the gall bladder may show bile imbibition. In advanced stages of post mortem degradation, the pancreas turns into a sac-like structure containing red-tinged fluid. It may even disappear leaving a flimsy membranous structure.

The Kidneys The kidneys may be discolored red from hemoglobin imbibition, and later discolored black (pseudomelanosis). The demarcation between cortex and medulla becomes not apparent. As time progresses, the organ becomes soft and gas bubbles form at the peri-renal tissues.

Spleen and Lymph Nodes The spleen may be discolored gray to black, becomes soft and mushy. Advanced stages of post mortem degradation usually turn the spleen into a sac-like structure containing liquefied parenchyma that oozes when cut. The lymph nodes may be discolored, become soft and pulpy.

Lungs and Airways Normal lungs are pale pink in color. After death, post mortem congestion becomes evident apart from livor mortis. Blood and fluid may ooze when the surface is cut. The airways may contain considerable quantities of froth and fluid. The organ becomes soft, collapsed, discolored red to gray, and gas bubbles may appear on the parenchyma as time progresses.

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The Heart and Great Vessels The heart becomes flabby, and may contain coagulated plasma separated from the red components of blood. The endocardial surfaces and the intima of great vessels may show reddish discoloration following hemoglobin imbibition.

The Brain The brain, being located farther from the gut show delayed post mortem changes. Vacuolation of the brain parenchyma due to seepage of cerebrospinal fluid may be observed. With advanced stages of post mortem degradation, the brain turns into a soft mushy mass. Later, the brain liquefies and will ooze when the calvarium and meninges are opened.

Muscles Discoloration of the muscles, fascia and tendon sheath occurs after death because of seepage of myoglobin. Intense coloration of the muscles may be seen at the down side of the animal. Air pockets demarcating muscle groups and fascial places occur in advanced stages of degradation.

The Eye The cornea of the eyes turns opaque due to absorption of the aqueous humor. The globe may either protrude or collapse. When opened, detached retina may be noted.

Body Cavities and Orifices Surfaces of body cavities may show discoloration following hemoglobin imbibition and pseudomelanosis. The cavities may contain red-tinged fluid and may be copious in its amount. Gaseous distensions render the carcass to appear bloated. It is not uncommon to find post mortem rectal or vaginal prolapse because of developing internal pressure. Straw-colored fluid may be seen oozing from body opening in advance stages of post mortem decomposition.

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3

Chapter

Routine Necropsy

T

he routine procedures for the necropsy examination of domestic animals will be described first. To illustrate the technique, the dog will be used as the model for the methods employed. Before necropsy, evaluate the clinical history of the animal to have an idea of what organs or organ system should receive particular attention. Although the examination of all organs and systems is recommended, prior knowledge of the clinical history serve as a guide in knowing what to look for and what specimens should be collected to confirm the diagnosis. Specimens submitted for necropsy should be examined following a set of routine. Two methods are traditionally used in the necropsy examination of domestic animals: Routine necropsy, and cosmetic necropsy. Cosmetic necropsies are most often sought by the owner of companion animals, particularly dogs and cat owners and shall be dealt with in another section. This section shall deal with the routine necropsy procedures. The procedures for the routine necropsy examination of dead carcass can be conveniently divided into three major stages: 1) Dissection stage - consist of preliminary incisions to expose the various organs and body cavities for the examination. 2) Display stage - the stage where all organs are exposed but remained on their original position and relations. 3) Examination stage - the part of necropsy where specific organs and organ systems are systematically examined one after another.

DISSECTION STAGE Position the specimen with its left side down, with the feet facing the examiner (Figure 1). Carefully examine the animal's exterior. Note the body openings for the presence of secretions/excretions, prolapse, and color of mucus membranes. Examine the hair coat, and note for the presence of ectoparasites, areas of alopecia, thickening of the skin, crust formations, tumour masses, and possible wounds. Penetrating

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wounds should be probed and the extent or depth noted. Palpate the continuity of bony structures and look for evidences of fractures and abnormal masses. Work with the right side of the specimen. The first incision is a straight line from the chin towards the ventral midline of the neck. Make an incision beginning from the chin and expose the mandibles and masseter muscles. Skin the neck and expose the underlying structures. Continue skinning backward to the flank of the right forelimb. Grasp and lift the right forelimb upward and cut all muscles between the subscapular area and the rib cage to free the limb. While doing this, locate, slice and examine the prescapular and axillary lymph glands. Examine the size and color and texture of the glands. After cutting all attachments of the forelimb, reflect the limb to the dorsum of the specimen (Figure 2). Hold the right hindlimb and cut the skin and underlying muscles of the hind flank. Expose the rim of the hip joint. With the aid of the tip of the knife, cut the round ligament to free the head of the femur and consequently the hindlimb. While doing this, take note of the articular surfaces of the acetabulum and the femur. Note also the amount, quality and quantity of the synovial fluid, and the appearance of the joint structures.

Figure 1. Position of the animal for necropsy. Arrows indicate the course of primary incisions.

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Figure 2. The specimen after skinning and cutting the attachments of both limbs. Broken lines indicate the cuts that should be made to open the thoracic and peritoneal cavities.

Reflect the freed hindlimb to the dorsum of the specimen. Continue skinning the ventral midline of the specimen from the incision made at the region of the rear flank and backward to the hind flank are. Reflect the skin at the dorsum of the specimen. While skinning the specimen, take note of the quality of the carcass in terms of the amount and appearance of the flesh. Note for any discoloration, bruises and prior bleeding points. The next step is to open the buccal cavity. To do this, cut deeply the submandibular muscles and underlying structures close to the inner rims of the mandible at both sides. With the aid of an ordinary pruning shear or costotome, split the mandibles at its symphysis. Alternatively, a hacksaw may be used to do this. Grasp the tongue and pull it backward. Cut all muscular attachments to free the tongue. Severe the hyoid bones at the articulation of the great and the small cornu. Free the tongue by cutting all structures behind the tonsillar tissues. Examine the palate, pharyngeal mucosa, and tonsillar tissues. Drag the tongue backward and dissect the trachea and oesophagus cutting all attachments up to the thoracic inlet. Leave the freed tongue, oesophagus and trachea still attached at the thoracic inlet. The abdominal cavity is then opened. Palpate the free edges of the last rib and make a shallow incision sufficient to cut the abdominal muscles and peritoneum at this region while not cutting deeper structures. Lift the opening and continue cutting the abdominal wall from the dorsum and into the area of the xiphoid cartilage of the sternum. Continue cutting the abdominal wall at its dorsal and caudal boundaries down 24

to the inguinal region. While this is done, note for the presence of ascitic fluid. Save as much fluid as possible for measurement of volume. Be careful not to cut the intestinal segments while doing this maneuver. After exposing the abdominal organs, leave the omentum that covers the intestinal loops for a while to avoid drying of the exposed segments. Position the knife at the angle formed by sternal part of the diaphragm and the xiphoid cartilage of the sternum. Cut the sternal part of the diaphragm and note the presence or absence of negative pressure within the thoracic cavity (Figure 3). The presence of a negative pressure is suggested by the backward displacement of the diaphragm. Continue cutting the costal part of the diaphragm close to the inner rims of the ribs. The right side of the rib cage is then severed from its attachment to the sternum. In young subjects, cutting the costo-chondral articulation with the aid of a knife can easily do this. Old subjects may require the use of ordinary pruning shears or costotome. Cut the costo-chondral articulation from the last articulation and towards the first rib. Be careful not to severe the tongue, trachea and oesophagus lying freely at this region. Detach the wall of the rib cage by cutting the neck of the ribs and associated intercostal muscles to expose the thoracic organs. The pelvic cavity is then opened. This is done by sawing the ilium close to the rim of the acetabulum at both sides (Figure 4). Then, saw the ischium from behind at both sides. Remove the sawed portion of the pelvic bone by cutting all underlying attachments to expose the pelvic cavity and its contents. At this point, the buccal, thoracic, abdominal and pelvic cavities and their contents are exposed for detailed examination.

DISPLAY STAGE The display stage is that part necropsy examination when all the organs are exposed for close inspection. This stage is the best time to examine the whole carcass where all organs are exposed and remains untouched. Examine the exposed organs and note their relations, position, and external appearance. Lift carefully the organs for a much-detailed examination of the whole structure. Exercise extra care so as not to unnecessarily displace the organs at this stage. If frank or clotted blood is present in any of the body cavities, carefully look for possible bleeding points. Should this be noted in the abdominal cavity, take particular attention to the surfaces of the liver and look for small fissures and cracks on the surface. In most traumatic conditions (e.g., vehicular accidents involving small animals), fissures and cracks on the liver parenchyma may be subtle or not readily apparent. Unfortunately, handling may easily produce the same and thus information concerning this condition is easily lost or overlooked. Manipulation and unintentional cutting of blood vessels may leak blood into the body cavity and make the appreciation

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of internal bleeding difficult. However, antemortem bleeding into the body cavity usually has accentuated lymphatic vessels filled with blood. Evidence of gastrointestinal accidents (torsion, volvulus, intussusception, strangulation, rent and tears in the omentum and mesenteries) is best examined at the display stage. Excessive manipulation of organs could easily dislocate relationship of organs, making the examination and recognition of strangulation, volvulus and intususception difficult. Similarly, small holes in the omentum or mesentry caused by abdominal accidents most often are overlooked, easily lost, or inadvertently produced. Should specimens for laboratory examination be required, the display stage is the best time to collect the required samples. Tissue blocks intended for histopathological studies should be collected at this stage. This is recommended since excessive handling of organs and tissues during the examination stage will most often produce artefacts in tissue sections. After carefully observing the organs at this point, the detailed examination of any organ or organ system follows.

EXAMINATION STAGE Examination of the Abdominal Organs The abdominal organs, particularly the gastrointestinal tract takes priority in the examination of organs. Their content of enzymes and bacterial flora render these organs to undergo rapid post mortem autolysis. It is desirable to remove the entire alimentary tract from the rest of the carcass. This will minimise soiling of the carcass with spilling digesta from the opened alimentary tract segment. Remove the whole segment of the gastrointestinal tract. To do this, grasp the large intestine and cut its mesenteric attachment. Cut the portion of the large intestine as it enters the pelvic cavity. While holding the cut segment of the large intestine, severe the mesenteric attachment of the large and small intestine. This will free the whole segment of the gastrointestinal tract. Grasp the whole structure, including the stomach and spleen and expose the duodenal loop where the bile duct opens. Gently press the gall bladder and note if the bile would flow freely from the bile duct towards the duodenal loop. A small cut at the segment of the duodenum where the bile duct opens may be required to determine this condition. Then, grasp the body of the stomach and gently press the cardia and the oesophagus close to the oesophageal hiatus of the diaphragm. Free the stomach the segments of the intestines by cutting the oesophagus. Remove the spleen by cutting the omental attachment from the body of the stomach. Place the whole gastrointestinal segments on one side of the table. With the aid of a pair of scissors, the stomach is first opened by cutting from the cardia and down at the greater curvature towards the pylorus. Spread open the stomach and gently 26

remove its contents. Examine the contents and qualify and the thickness of the walls. Note for the presence of ulcers, evidence of calcification, strictures, perforations, foreign bodies, and exudates. Free the entire length of the intestine by cutting close to the mesenteric attachment segment by segment. While freeing the duodenum, exercise care not to damage the pancreas which should be examined at this stage. Note for nodule formations, colour, and texture of the organ. Examine also the adjacent adipose tissues and look for evidence of necrosis of fat. Cut open the intestine as the segment is freed from its attachment. Some workers suggested that the whole segment of the gastrointestinal tract be opened. While this is ideal, the time involved in opening the whole segment may be staggering. For an average sized animal, this may reach to four meters and consequently require much time. Also, the subdivisions of the intestinal tract may not be appreciated if the whole segment is freed and lying as a straight tubular structure on the table. Moreover, accidental cutting of segments may leave the examiner losing track of the continuity of the structure. As an alternative, the intestines may be examined leaving their mesenteric attachment intact. Locate and open a representative segment of the duodenum, jejumum, ileum, caecum and colon. Examine the contents, the appearance of the mucosal surfaces, thickness of the walls, presence of ulcers and strictures, foreign bodies, and exudates. Qualify the color, odour, and consistency of the contents. Samples taken from the segments of the gastrointestinal tract intended for laboratory examination should be evaluated as to its relative merits. Considerations should include the time elapsed since death of the animal.

Examination of Thoracic Organs The next step is to examine the thoracic organs. Removal of the organs from their attachments in the thoracic cavity is recommended. To do this, grasp the tounge, trachea and oesophagus lying close to the thoracic inlet. While lifting these structures and pulling backwards, cut the pleural attachments of the lungs. Severe the aorta and other vessels to free the lungs and the heart. Lay the freed organs at one side of the table. Inspect the dorsal and ventral surfaces of the tounge. Note for the presence of ulcers and suppurative foci and wounds. Palpate the tounge muscles and look for nodules or abnormal masses. Inspect the thyroid and parathyroids at both sides. Cut open the whole lenght of the oesophagus and examine the mucosa for the presence of ulcers, strictures, and abnormal tissue masses. Open the trachea and examine for haemorrhages, fluid or froth content, foreign bodies and broken cartilage rings. Continue examining the trachea down to its minute bronchial terminations in the lungs. Look for evidences of dilatation, collapse, foreign bodies, fluid and/or froth content. Animals that died from lung oedema may show a stable froth in the trachea. Examine the surfaces of the lungs and pleural investments by ocular inspection and 27

palpation. Look for changes in colour and consistency of individual lobes, collapsed or dilated lobes, and for the presence of abnormal tissue masses. Areas of consolidations should be characterised as to location and degree of involvement of lung parenchyma and its distribution. An apical distribution is most often an indication of bronchopneumonia.

Examination of the Heart and Blood Vessels It is convenient to examine the heart that is still attached to the lungs. Grasp the heart on one hand and examine the outer surfaces of the pericardial sac for thickness and transparency. Open the pericardial sac and note the colour, tubidity, amount and quality of pericardial fluid. Examine the pericardium and note for haemorrhages and the amount of fat in the pericardial groove. Qualify the shape of the heart and note any change in the bulk of the chambers. Grasp the heart by one hand and rotate it so that the anterior surface faces upward, with the right chamber facing the examiner. As an aid in orientation, the triangular extremity of the right auricle and the pulmonary artery would point at the direction of the examiner's right side when the heart is rotated. Cut open the right auricle starting from the site for entry of the posterior vena cava and horizontally towards the opposite extremity. Remove any clotted blood and examine the patency of the tricuspid valves and the inner surfaces of the right auricle. Position the knife inside the right ventricle. Cut the muscle close to the septum starting from the examiner's left side then downwards and into the entire length of the pulmonary artery. This will form a V-shaped flap of the right side of the heart. Continue opening the pulmonary artery and its branches deep in the lung parenchyma. Examine the thickness of the right chambers, the tricuspid valve and associated papillary muscles, and the endocardium. 28

Figure 5. Opening the Right Chambers

Figure 6. Opening the left chambers

Rotate the heart until the left auricle faces the examiner. Make a horizontal cut at the left auricle extending to its extremities. Remove any clotted blood and note the patency of the bicuspid valve. Open the left ventricle by positioning the knife vertically into the chamber wall. Cut open the wall down to the apex. Examine closely the bicuspid valve and the papillary muscles. After doing this, position the knife into the opening of the aorta which is partly covered by the bicuspid valve. Cut open the valve and the aorta. When all the chambers have been Figure 5. Opening the heart while still opened, compare the thickness of the attached to thoracic viscera muscles and valves. For the heart valves, note its thickness, presence of strictures and/or local tissue masses, and torn moderator bands. Examine the endocardial surfaces and note for areas of haemorrhages, egenerations, fibrosis, anomalous openings among others. Then, examine the lumen of great vessels and note for evidence of regurgitation of blood. At this point of the examination, go over the rest of the carcass and cut open the entire length of the aorta down to the iliac bifurcation. Look for possible areas of thrombosis.

Examination of Other Visceral Organs The examination of the rest of the organs still attached to the carcass follows. Examine the intact and cut surfaces of the liver and note for colour, texture, consistency, changes in the acinar patterns, abnormal masses among others. Make several slices of the liver for closer inspection. Cut open the gall bladder and note the quality and colour of bile, and the appearance of the mucosa. Examine the adrenal glands which are located above the anterior pole of both kidneys. Cut them open longitudinally and note the relative thickness of the cortex in relation to the medulla. Carefully remove the kidneys from their attachments without severing the ureters. Grasp the kidney gently between one hand and cut it into halves longitudinally. Examine the kidneys for haemorrhages, areas of necrosis and/or infarcts, evidence of mineralisation, and compare the thickness of the cortex to that of the medulla. Trace the opening of the ureter and cut it open until it enters the urinary bladder. Puncture the urinary bladder and collect the urine and measure the volume. Cut open the urinary bladder and note for areas of haemorrhages, necrosis, presence of stones, and fibrosis. 29

For male animals, slice and examine the prostate and cut open the urethra up to the penis. Look for possible small calculi that usually lodge at the urethral flexure. In female animals, free the vulva and the vagina from their attachments in the pelvic cavity. Cut them open and examine.Lymph nodes are examined whenever they are encountered during dissection. In cases of suspected malignancy, it is imperative to examine the regional lymph node and look for evidence of metastases.

Examination of the Brain The examination of the brain requires removal of the head from the rest of the carcass, and opening the calvarium. To remove the head from the rest of the carcass, severe all attachments at the atlanto-occipital joint. While doing this, take care not to unnecessarily pull the spinal cord damaging it on the process. Skin the head and remove all muscles to expose the vault of the cranium. To open the vault of the cranium and expose the brain, a hacksaw may be used to saw off the overlying bones. Alternatively, a chisel may be used but take care not to penetrate the cavity and damage the brain. If a vise is not available to hold the severed head in position, grasp firmly the head and press it against one corner of the table Figure 10. Sample skull of the dog. Arrows illustrate the and carefully saw the bone lines where the cuts shall be made. slowly. Hold the head firmly with the aboral surface (occipital bones) slightly tilted and facing the examiner. A mechanic hacksaw may be used to saw off the overlying bones. Alternatively, a chisel may be used but take care not to penetrate the cavity and damage the brain. If a vise is not available to hold the severed head in position, grasp firmly the head and press it against one corner of the table and carefully saw the bone slowly.

Hold the head firmly with the aboral surface (occipital bones) slightly tilted and facing the examiner. Grasp the whole head with one hand pressing the thumb against the nasopharyngeal openingAnchor the index finger on the orbital rim and support the nasal region with the rest of the fingers. Press firmly the head on one corner of the table. Carefully saw the condyloid fossa just above the occipital condyles. Continue the 30

cut slightly oblique and forward cutting the junction of the squamous temporal and occipital bones, and up to the supraorbital process of the frontal bones. Take care when cutting the lateral part of the temporal bone since at this part the bones are relatively thin and lie close to the brain. After completing cuts at the right side of the head, rotate the head to cut the bones at the other side. Grasp the head with the thumb anchored on the orbital rim and the index finger pressed against the nasopharyngeal opening. Support the head using the rest of the fingers grasping the nasal region. Make a similar cut until both the cuts at both side of the head meet at the median plane. Place the head on the table and hold it firmly with one hand. Make a diagonal cut continuing the cuts made at either side, and saw off about quarter thick of the head. This completes the cuts to open the calvarium.

Hold the head slightly tilted with the foramen magnum facing the examiner. To remove the sawed portion of the calvarium, pry it open by sticking the knife or a flat instrument onto the sawed portion where the occipital and temporal bones meet forming a ridge. This part of the skull is relatively thick. Twist the knife and force open the sawed bone. If the cuts made were deep enough, this should pry open the calvarium without much difficulty. Once the sawed portion is lifted and removed, cut the meninges covering the brain. The brain is now exposed for examination. Before removing the whole brain from the cavity, examine the surface of the brain and look for evidence of oedema such as cerebellar coning and flattening of the gyri and sulci. Remove the brain by inverting the head with the palm supporting the falling brain. With the aid of a pair of scissors, cut all the cranial nerves and attachments until the whole brain drops slowly to the palm of the hand holding the head. The whole brain is best fixed in ten-times the brain volume of 10% formalin solution overnight before examination. This will harden the brain and makes it amenable to slicing and manipulation. Detailed examination of the brain requires making serial sections no thicker than 0.5 cm. In looking for possible lesions in the brain, the idea of duplication in the appearance of both sides of the brain should be considered. Any alteration on the appearance of one side compared to that of the other side may be a suspect for possible lesion, provided that cuts were made perpendicularly. When slicing the brain, note any difference on the diameter of the ventricles and any abnormal tissue masses. Save the slices of the brain in fresh formalin solution. For routine histopathological evaluation of the brain, at least six sections are required composed of the following transverse sections: 1) Root of spinal cord 2) Mid cerebellum 31

3) Cerebrum at either side (2 sections) including the hippocampus 4) Brain stem taken at the level of the pons 5) Cerebral peduncle

Examination of the Spinal Cord Clinical history of sudden and/or progressive paralysis warrants the examination of the spinal cord, nerve plexus, and associated ganglia. Remove the entire spinal column by sawing off all attachments of the ribs at either side and muscles. Cut the spine from the rest of the carcass at the articulation of the last lumbar and first sacral vertebra. Remove as much muscles as possible. Note for evidence of fracture and/or dislocations. The spinal cord should be removed by opening the spinal column. Two approaches may be used to do this. First, the spinal column may be split Figure 11. Diagram of the vertebra showing the sites (dorsal through the aid of a saw cutting arches and/or splitting of the vertebra) where the cuts should be made. about one third of the vertebra, and second, by removal of the dorsal arches. Splitting the vertebral column enables the examination of the intervertebral discs and vertebral canal. To do this, hold the spinal column with one hand pressing it on the far end of the table. With one or three vertebral bodies extended beyond the edge of the table, carefully saw the vertebral body longitudinally. Keep the blade of the saw positioned medially to the spinous process cutting the dorsal arches and the vertebral body at one side. Complete the cuts until the whole length of the spinal column is split open adjusting the Figure 12. Illustration showing the the sawed segment of the spinal column by splitting extended portion one or two the verterbra. 32

vertebral bodies at a time as cuts are made. While sawing, be careful not to damage the enclosed spinal cord. Once the spinal column is split opened, mark the specific regions (cervical, thoracic, and lumbar regions) using pins or by loosely tying pieces of twine at each division. Lift the cord by grasping the spinal meninges and severe all attachments. The second alternate method employs the removal of the dorsal arches. This may be accomplished using a chisel cutting the arch of each vertebral body. For large animals however, it may be convenient to detach first the individual vertebral bodies and saw off the dorsal arches. The spinal cord, like the brain is best examined after fixation in 10% formalin solution. After fixation, remove the meningeal covering. Hold the cord vertically on one hand. Gently palpate the cord passing it between the thumb and the index finger. Note for pits and depressions, and difference in texture. Examine also the vertebral canal and note for narrowing of the lumen, evidence of fractures, and character of the intervertebral discs. Evidence of disc degeneration includes dryness and changes in the colour of the disc (from yellowish to greenish) with or without apparent protrusion into the spinal canal.

Examination of Bones and Joints Bones and joints are seldom examined unless the clinical history suggests lameness. Also, by doing the examination samples of bone marrow which often reveals some clues on the haemopoeitic status of the animal could be collected for laboratory examination. While the hip joint is probably the most accessible joint usually examined during the dissection stage, other joints may be included should the need arises. To open the stifle joint, skin the hind leg. Cut the quadriceps femoris muscle at its tendon lying on the anterior surface of the hindlimb overlying the patella. Slit the tissues at both sides of the patella and expose the distal articular surfaces of the femur and proximal part of the tibia. The almost flattened fibrous structure located between the distal articular surface of the femur and proximal surface of the tibia are the menisci and ligaments of the joint capsule. Dissect and examine these structures. Examine the articular surfaces of the bones for evidence of erosion, cracks and fissures, and the presence of osteophytes. Note also the character, colour, amount and consistency of synovial fluid including the synovial membranes. Reactive synovial membranes usually present small papillae which are best recognised by submerging the specimen in water or saline. Following the examination of the stifle joint, remove the femur for evaluation of the bone and bone marrow. Split the bone longitudinally into halves using a hack saw. Examine the cut surface of the bone. Note the amount of compact and spongy bone material.

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Examination of Eyes and Ears The examinations of eyes and organs of hearing are seldom done unless clinical history suggests otherwise. The eyes are best examined at the first instance. Since the eyes often do not allow easy handling, it is best to have them fixed in formalin. To examine the organs of hearing, examine the middle external ears, then trace and cut open the external ear canal and note its contents. Examine the middle ear by opening the tympanic bullae and note its contents.

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4

Chapter

Cosmetic Necropsy

T

he bonds between owners and their pets have progressed to a point that pet animals are no longer considered as mere pets but members of the household. This is particularly true for dogs and cats that have been elevated to a certain position in the society where their principal role is not just to provide companionship, but as part of the family. Society has changed and currently recognizes the rights of these animals. Thus, in cases of unexpected death, the dead animal body is accorded equal respect. Accordingly, it is not uncommon to find pet owners objecting in part to have their pet be a subject for necropsy examination. While it may be argued that pet owners do not object to the aim of the necropsy per se, what might be intolerable are the procedures employed in routine necropsy. As evident by now, routine necropsy accompanies dismemberment of body parts eventually turning the dead carcass into one heap of dissected bones and flesh. This obviously would be revolting to some pet owners who would most likely want to have their pet a decent burial in one piece. Despite the development of techniques of post mortem examination in human medicine, the autopsy procedure itself being cosmetic in nature, description of the same technique in animals remains to be developed. While veterinary students are taught the procedures for routine necropsy, the incorporation of a suitable technique that will not hurt the sensibilities of pet owners received little attention. Thus, when confronted with such a case, students and practitioners alike hardly had the interest to pursue the necropsy examination. Cosmetic necropsy, as the term suggests employs methods aimed at limiting the procedures that will disfigure the carcass while maximizing the information gained during necropsy. As such, cosmetic necropsy requires carefully planned incisions and the methods for the restoration of the specimen into its original appearance after the examination. The proceeding sections attempt to define the basic procedure for cosmetic necropsy of domestic animals, with the dog as the animal model.

PRELIMINARIES As in routine necropsy, the exterior of the animal should be carefully examined. Evaluate the clinical history and decide which organs of organ systems must be 35

examined. Evaluate the conditions by which such organs will be made accessible considering the limitations of the cosmetic necropsy procedures. Should examination of the same will produce unsightly incisions and cuts, it is best to explore the alternatives and discuss these with the pet owner. If the intentions are discussed exhaustively with the pet owner describing the benefits of doing such an examination for the formulation of a diagnosis, consent may be sought with little difficulty. Under no circumstances that extra incisions and maneuvers be made without the owner's consent. Even then, the standard cuts that will be mentioned in the proceeding sections should be cleared with the owner to prevent possible misunderstanding and unfavorable outcomes.

NECROPSY PROCEDURES The rule of thumb in cosmetic necropsy is to limit the number and the length of incisions to as few as possible. In planning the incisions, a few things must be considered: 1) The organs or systems that must be examined; 2) The site for incisions that will not disfigure the specimen, and with due considerations that the incisions would not be so obvious once sutured back to place; 3) The length of the incision considering the accessibility of the organs; and 4) The time that will be involved in the examination.

The best approach is to position the animal lying on its back (dorsal recumbency). The head of the carcass should face the left side of the examiner. Sandbags or other objects placed at either side of the thorax would help to hold the carcass in place. Using a sharp knife, make a straight longitudinal incision on the skin only from the xiphoid cartilage of the sternum and to the midabdomen. Dissect the skin towards the side taking care not to damage the hide,

Figure 13. Illustration showing the lines of incision for cosmetic necropsy.

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and expose the underlying tissues. Open the abdominal wall by cutting open the abdominal muscle at the exposed site. Note for the presence of fluid and try to assess the arrangements of organs. Retract both sides of the opened abdominal wall and reach for the diaphragm. From this small opening, puncture the diaphragm and note for the presence of a negative pressure. Open the thoracic cavity by cutting the diaphragm close to the inner walls of the rib cage. Grasp the thoracic organs and free them from their attachments. Drag the thoracic organs en masse and reach for the esophagus and trachea at the thoracic inlet. Cut free these structures and set them aside for examination later. From the same opening at the abdomen, grasp the visceral organs out of the cavity and severe all attachments. Remove first the liver, and then the stomach with the spleen. Drag the segments of the intestine and cut the mesenteries close to the intestinal wall segment by segment. Remove the intestine and set them aside for examination. Reach for the kidneys at both sides and severe them from their attachments. Palpate the urinary bladder, and if required, reach for it and severe its attachments. After these, examine the visceral organs as with routine necropsy. After removal of most organs, it is recommended to drain the carcass of blood and other body fluids. If needed, the body cavities may be washed with saline or tap water. Examine the body cavities and allow the carcass to drain. The examination of the brain should only be done if clinical history suggests neurological disturbance. To remove the brain from the bony calvarium, make a midline incision from Figure 14. Illustration showing the between the eyes and towards the procedures for opening the brain level of the first cervical vertebra (atlas). Dissect the skin and reflect all muscles covering the calvarium, cutting them towards the side. The vault of the cranium is best opened using a mallet and a sharp chisel. With the skin and muscles reflected at either side, cut the bone starting from the frontal region and around the exposed portion of the vault of the cranium. Take care not to damage the enclosed brain. After removing the vault of the cranium, cut the meninges 37

to expose the brain. Severe the spinal cord and lift the brain carefully. Cut all the nerves at the vase. Tilt the head upward and backward to simplify removal of the brain from the cranial cavity.

POST EXAMINATION One basic requirement of cosmetic necropsy is to restore the animal carcass back to its original state as much as possible. Sutures should close all incisions, and soiling of the hide by blood and body fluids should be cleaned. After examination of organs and before suturing back the incisions, the organs examined may be returned to the body cavities to give form to the carcass. Alternatively, the spaces may be stuffed with old newspapers that while giving forms to the hollow cavities, it also absorbs much of the remaining blood and body fluids. In closing the incisions made a continuous suture on the skin using heavy twine and surgical needle will be sufficient. In restoring the form of the head following removal of the brain, replace the chiseled vault of the cranium. Suture back the reflected skin at this site. Neat sutures and arranging the hair or fur will sufficiently hide many sutures. Other organs and body parts may be examined when deemed required, planning all incisions and suturing them back is required. While cosmetic necropsy provides some ways by which dead animal carcasses may be examined without hurting the sensibilities of the owner, some organs or body parts (example, the spinal cord) may be difficult to reach using this method. As was previously discussed, it is best to discuss with the owner all the necessary procedures that will be done in the carcass. Doing so assure confidence and by that maximizes the information gained during necropsy examination.

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5

Chapter

Avian Necropsy

N

ecropsy examination of the fowl present special problems. First, diseased or dead birds submitted for necropsy examination most often come from a large flock. Thus, there are no guarantees that the bird samples submitted represent the true picture of the health status of the flock. Isolated cases of diseases are therefore possible, and information gained following necropsy may thus be difficult to interpret for the rest of the flock. The basic question that must be answered is whether necropsy examination will shed light on the disease process affecting a significant proportion of the flock. Therefore, for necropsy examination to be meaningful, careful sampling of the flock is essential, and that samples submitted for necropsy should be those representing a wide spectrum of clinical signs observed on the flock. It is best to submit birds that are showing the earliest signs of the disease in question, at its worse state, and include also those dead birds that succumbed from the disease in question. Second, avian species tend to have a limited repertoire of signs following disease, such that critical history taking is essential. Moreover, it is generally recognised that most avian diseases are multi-factorial in aetiology. Information on the type of housing, ventilation, diet, husbandry practices, sources of stocks, number of birds affected, the stage of production, and the rapidity by which the disease spread of in terms of days elapsed following the appearance of the clinical signs should be obtained to properly evaluation the situation. Third, diagnosis of most avian diseases requires ancillary laboratory tests apart from necropsy. In most cases, there are no substantial gross changes that may be considered diagnostic, although clues may be derived from these gross changes on the best laboratory test that must be employed. Fourth, it must be remembered that species difference exists, and that the examiner should be aware of these differences between and within species of birds. Many veterinarians are caught off guard whenever species other than domestic chicken is presented for necropsy. The fact that birds has feathers lend themselves not amenable to physical examination, the feathers causing much difficulty for the examiner. Consider the number of birds submitted for necropsy for a given disease in question, this may require a considerable amount of time. Yet, physical examination is an essential prelude to necropsy. The proceeding discussions of the techniques for avian necropsy will use the domestic chicken as the model. The same technique may be easily adapted to the necropsy examination of most avian species.

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PHYSICAL EXAMINATION Birds submitted alive for necropsy should first be examined prior to euthanasia. A systematic approach in the physical examination of the samples should be done. Ruffling of the feathers to view the skin from the head and proceeding caudally is best. For live birds, take particular attention to the body conformation and the behavior of the birds bearing in mind what is supposed to be normal for the species, breed and age. Allow the birds to rest for a while if they were transported. If blood samples may be required, it should be taken at this stage.

Figure 15. Cervical disarticulation in domestic fowl. Note the positioning of the thumb and the rest of the fingers. Inset: Direction of pull.

Take note of any swelling on the infraorbital sinuses, discharges on the nostrils, beak deformation, feathering, distention of the crop, the appearance of the foot pads and cloacal discharges. With the aid of a magnifying glass, ruffle the feathers under the wings and around the cloaca and examine for the presence of ectoparasites. The skin should be examined for the presence of lumps, bruises, wounds and other abnormalities. In interpreting cloacal discharges, it must be remembered that the cloaca or vent is the common opening for both the alimentary and uro-genital system. Soiling of the feathers around the vent need not indicate gastrointestinal pathology. The discharges should be qualified as to nature, colour, consistency and odor.

EUTHANASIA Most avian species can be humanely killed by atlanto-occipital disarticulation. This technique however requires practice and care must be taken not to break the skin or totally obliterate the head from the neck makes a lot of mess. To do this, hold both legs and the wings with one hand. Grasp the head and neck with other hand. Secure the head between the thumb and the pointing finger. Position the thumb at the base of the neck and the pointing finger at the base of the lower beak. Hold the bird firmly and with a sudden jerk, twist the hand holding the head to disarticulate the neck.

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Large birds may react violently to the procedure such that adequate restraint is essential. Alternatively, chemical means of euthanasia may be done. For large birds, intraperitoneal or intravenous administration of barbiturates may be used. Small birds may be euthanased using inhalant agents such as chloroform or ether. Soak a piece of cotton in any of these agents and put it on a container with a lid. Place the bird on the container and close the lid.

OPENING THE BODY CAVITIES Minimal equipment is often required in fowl necropsy and these include a pair of scissors, forceps, bone cutter and a knife. Prior to opening the bird, it is best to wet thoroughly the whole bird in a detergent solution. This will lessen the chances of feathers floating around the area while the examination progresses. Lay the bird on a pad of newspaper on the table. The paper serves to absorb most blood and fluid, and provide a convenient wrapper for the carcass after examination. Position the bird so that the legs and feet are facing the examiner. For your birds, break the skin in between the thighs towards the back, disarticulating the hip joint on the process. This will enable the specimen to be laid down flat on the table. The skin at this portion of the body may be easily broken in most domestic fowl. In old and large birds however, this may not be easily done and incisions through the skin and adductor muscle using a knife may be required. Grasp and cut the portion of the skin still covering the abdomen and pull the skin towards the neck region exposing the abdomen and breast on the process. At this point, note the amount of flesh in the breast and thighs of the bird, and any discoloration on the subcutaneous tissues. Dissect the skin covering the crop and the neck. With the aid of a pair of forceps, lift gently the muscle at mid-abdomen and cut through it horizontally using a pair of scissors. While doing this, examine the paired abdominal airsac. Note the opacity of the sac and its contents if any. Continue the cut until it reaches both side of the abdomen and upward towards the last set of ribs. Lift 41

Figure 16. Skinning the bird. The skin is manually dissected from the abdomen to the neck region. Note the line of incision to open the abdominal cavity

the breast and cut the set of ribs at both sides. While doing this, examine the paired anterior and posterior thoracic air sacs. Free the breast from attachments of the liver and heart. Using bone cutter or a large heavy-duty scissors cut the pectoral muscle and clavicle at both sides to free the breast. Care must be exercised not to unnecessarily severe the trachea, syrinx, brachial vessels, or cut open the crop. Remove the freed breast. Next, position the bird so that the feet are facing the left side of the examiner and the head of the bird facing the examiner's left side. Open the mouth and insert the point of the scissors at the commissure of the beak. Cut the commissure of the beak and Figure 17. Schematic diagram of the relative location of the air sacs in domestic fowl. Ce- cervical; Cl- clavicular; continue the cut towards the throat. Locate the opening of the Ax- axillary; At- anterior thoracic; Pt- posterior thoracic; oesophagus and cut through Ab- abdominal air sacs. towards the crop. Examine the contents of the crop and the appearance of the mucosa. Do the same for the trachea and cut through towards the syrinx. While doing this, examine the thymii, thyroids and parathyroids which are located at the lower neck region and at the thoracic inlet. Reposition the bird so that the feet are facing the examiner.

DISPLAY STAGE Examine the organs in situ after completing the preliminary cuts to expose the visceral organs. As in mammalian necropsy, the arrangements of the organs, presence of fluids in body cavities, and evaluation of the appearance of most organs are done at the display stage. Also, samples for laboratory examination may be obtained at this stage. The relative size of the organs can be gauged at this stage, but the normal conformation for the species, breed and age should be known. Since most students of necropsy encounter difficulties identifying some structures in avian species, a short review follows. In birds, there is no structure homologous to the mammalian diaphragm. Thus, there is no distinct separation between thoracic and abdominal cavity except for two thin membranes, the pulmonary aponeurosis and oblique septum. The lungs are small 42

and are attached to the ribs. The liver is usually large and bi-lobed. A gall bladder may be present in some species (e.g., chicken, duck and goose) or may be absent (e.g., pigeons). The gizzard is usually reflected to the right side of the specimen. An ovoid spleen is positioned near the proventriculus. Segments of the intestines, caecum, and colon can be observed in the intestinal mass reflected with the gizzard. The duodenum forms a loop that accommodates the pancreas. From the duodenum, there is no clear demarcation into jejunum and ileum. A paired caeca is present, and a short large intestine is not clearly delineated into colon and rectum. This enters into the formation of the cloaca. The kidneys are lobulate and closely attached to the sub-lumbar region. The ureters open into the cloaca. A urinary bladder is absent in avian species. Located close to the cloaca is the bursa of Fabricius. A left ovary and oviduct are always found at the left side, the right structures being undeveloped. There are no lymph nodes in birds. The long bones usually contain air spaces with minimal amount of marrow at the extremities.

EXAMINATION STAGE The visceral organs in avian species may be examined in situ. If required, the liver, spleen, gizzard, proventriculus, and the whole intestinal tract may be detached to facilitate the examination of other organs. Grasp the proventriculus and cut the oesophagus. Lift the gizzard, the proventriculus, liver and the whole intestinal tract and severe their attachments. Cut the large intestine a short distance from the cloacal opening. Lay the severed organs at the table. Examine the liver and spleen. Open the proventriculus and gizzard longitudinally and note the contents and the mucosal surfaces. Peel the keratinised layer on the mucosal surface of the gizzard. Examine the pancreas and cut open the duodenal loop. Cut open the other parts of the intestine, preferably the whole segments. Note the colour and consistency of the contents, colour and appearance of the mucosa. Open the caecal junction and the caecum at either side. Examine the colour, consistency and appearance of the mucosa and its contents. Open the trachea down to the syrinx. Closely examine the mucosa of the trachea by sliding the blunt portion of the knife or scissors at the opposite side. Incise the lungs and note for any exudate and tissue masses. Remove the heart and make transverse section through it. Examine the kidneys, adrenals, ovaries/testes, and oviduct. Cut open the cloaca and examine its mucosa, contents and discharges. Locate the bursa of Fabricius and cut it open.

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Dissect out the muscles at the posterior portion of the legs to expose the sciatic nerves. Do the same for the other leg and compare the size of the nerve. Note for any haemorrhage on adjacent tissues. Examine also the brachial plexus by cutting the muscles between the scapula and the vertebral column. Note for any enlargements of the nerves. Examine the muscles, joints and tendons of the legs and wings. Remove the head from the rest of the carcass. Cut away the skin at the cranium. Using bone cutters or heavy duty scissors, cut the bones just behind the orbits and extend the cut caudally to the foramen magnum. Remove the cranial vault to expose the meninges and the brain. As in mammalian necropsy, fix the brain in 10% formalin solution prior to slicing. To remove the spinal cord, it is best to cut the dorsal arches of the spinal column, taking care not to damage the cord. Alternatively, severe the spinal column segment and fix them in 10% formalin prior to dissecting out the spinal cord. Figure 18. Display stage in avian necropsy

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