samples of most visceral organs, 24 hours is usually sufficient. Waste formalin is considered hazardous waste and must be handled following current state and federal regulations, as well as U.S. Environmental Protection Agency guidelines. Similarly, the size and quantity of formalin containers that can be shipped may be limited, which may be of particular importance when multiple samples are collected.
For shipping samples, four layers of packaging are generally required to include a primary watertight inner receptacle, absorbent material, a secondary watertight inner receptacle, and sturdy outer packaging. The second receptacle should contain any required clinical history and request forms. Both the shipping company and the receiving laboratory should be consulted to ensure proper packaging prior to sample submission. Remaining samples can be placed and stored in a large plastic container of formalin in case additional samples are needed.
5.4.2.4 Tissue Checklist for Necropsy
The following tissues should be preserved in 10% buffered formalin at a ratio of 1 part tissue to 10 parts formalin. Tissues should be no thicker than 1 cm.
1 Liver – sections from each lobe, including gall bladder
2 Kidney – sections should extend from cortex to medulla and be collected from each kidney (see Figure 5.5)
3 Stomach – sections from fundus (body) and pylorusFigure 5.5 Sections to be submitted for histological analysis need to be thin enough to properly fix in formalin. In this example, the (a) kidney has been cut along a (b) mid‐sagittal plane. (c) A properly cut section for fixation in 10% buffered formalin is pictured.
4 Gastrointestinal (GI) TractOral/pharyngeal mucosa and tonsil – plus any areas with erosions or ulcerationsTongue – cross section near tip including both mucosal surfaces Segmental (up to 5 cm long) sections of:EsophagusSmall intestines – duodenum, jejunum, ileumLarge intestines – cecum, colon
5 Spleen
6 Pancreas
7 Adrenal gland
8 Heart – longitudinal sections including atrium, ventricle and valves from both left and right sides
9 Lung – regional samples including cranioventral, caudodorsal, and hilar with major bronchus included
10 Lymph nodes – possibilities include iliac, mesenteric, hilar, mandibular, retropharyngeal
11 Thymus (if young animal)
Other possible tissue sections to consider (case dependent):
1 Skin – any affected regions
2 Brain – if there are neurologic signs, the entire brain should be submitted, cut longitudinally along the midline
3 Reproductive tract – entire uterus and ovaries with longitudinal cuts into the lumen of uterine horns, or both testes (transversely cut) with epididymis
4 Salivary gland
5 Trachea
6 Nasal turbinates
7 Thyroid/parathyroids – leave intact
8 Urinary bladder, ureters, urethra‐ cross‐section of the bladder and 2 cm sections of ureter and urethra
9 Eye – intact
10 Spinal cord (if neurologic disease)‐ sections from cervical, thoracic and lumbar cord
11 Skeletal muscle – diaphragm, cross‐section of thigh muscles
12 Bone marrow – Opened rib or longitudinally sectioned ½ femur; marrow must be exposed for proper fixation
5.5 The Diagnostic Shelter Necropsy
Consider the following case history:
There is an outbreak of diarrhea, with a concurrent increase in mortality, in cats and kittens in a large, municipal shelter. Several cats and kittens have been found dead within the past few weeks. The bodies were disposed of and the cages cleaned thoroughly but even with isolation procedures in place, the number of affected animals appears to be increasing. The shelter manager and part‐time veterinarian at the shelter both suspect that the feline panleukopenia virus is the culprit. Animals are vaccinated at intake and every two weeks during their stay, but the disease presentation seems more aggressive than they have seen in the past, and several older cats have been affected. A fecal antigen test was performed on two affected animals, but the result was negative for viral antigen on the first and weakly positive on the second animal. Although apparently well yesterday, a cat and a three‐month old kitten were found dead at morning rounds. They believe both animals are part of this outbreak, although diarrhea was seen in the cat's cage but not in the kitten's cage. What is the best way for staff to establish the cause of gastrointestinal disease in their feline population?
This scenario is not at all uncommon in shelters. If accurate (sensitive and specific) pre‐mortem tests are available and results are consistent in affected animals, a cause for increased morbidity and mortality is comfortably determined. However, there are many reasons (e.g. less sensitive test, unusual presentation for a disease, unusual behavior of the disease in a population, non‐responsive to treatment for that disease) a shelter might seek additional information about a disease. In this case, although feces from one cat was positive for the presence of feline panleukopenia virus, the disease seemed to be occurring in the face of vaccination and isolation and was occurring in animals less commonly associated with the suspected disease (older animals).
What should they do? Staff are understandably very busy and need to efficiently diagnose the problem. The tests have been somewhat equivocal and doing full necropsies on each of these animals would likely be very time‐consuming; moreover, they are not sure the gross exam will be helpful since they are not exactly sure what they are seeing.
In a shelter (herd) situation, it is sometimes practical, sufficient, and time‐efficient to ask a more specific (limited) question about disease or death of an animal. Gastrointestinal and respiratory diseases, in particular, are frequent problems in shelters. To ask a more limited question of a necropsy means that the necropsy itself can be simplified. Necropsy samples can be the best samples to definitively diagnose a cause of disease, and proper necropsy sampling in a sentinel case or an infectious outbreak will save other animals.
5.5.1 Sampling a Carcass, General Considerations
The success of infectious disease diagnosis depends largely on the quality of the specimen and the conditions under which the specimen is transported and stored before it is processed in the laboratory. It would be naive to generalize; depending on the suspected agent and the test, the optimum sample and optimum conditions for stabilization during transport are variable. For example, if a bacterial agent is suspected, freezing the specimen could compromise future culture; however, DNA would remain intact and a PCR test relying on extracted bacterial DNA would be unaffected. Some viruses, on the other hand, can withstand freezing, especially if samples are stored in the proper media. There are specific transport media that stabilize viruses and prevent bacterial overgrowth. What this means, of course, is that if the cause of the disease is completely open and multiple tests are going to be performed, multiple types of samples
