Dr. Jenni Bass
Should you decide to have a necropsy performed on your pet, your reptile veterinarian will start by taking a thorough history of the animal, the husbandry conditions and the signs, or symptoms it showed before death. Obviously, if the animal experienced a protracted illness, or was under veterinary care when it died, your vet will already be familiar with the events preceding the loss of your pet. The cause of death may already be suspected. The results of tests performed when the animal was alive may have yielded a diagnosis or clues as to where to look during the necropsy.
If the animal is one of several in a collection, your veterinarian will want to know the health status of other animals and whether or not there were any recent introductions to the group, changes in husbandry or medical therapy. Again, records can prove extremely useful. Important details may come to light in a retrospective consideration of records, which ensure that the most information possible is gained from the necropsy, and increases the likelihood that the factors that led to the death of the reptile will be determined.
Depending on the case, your reptile veterinarian may perform the necropsy himself, or he may send the body to a veterinary pathologist. His decision will be based on the particular features of the case. For example, if a zoonosis (a disease transmissible from animals to man) is suspected, precautions may have to be taken during the procedure and in disposal of the body, which require facilities found only in laboratories or some veterinary practices.
Whether for financial reasons, or because the cause of death has been determined early in the process, not every necropsy will involve every step listed below. The veterinarian or veterinary pathologist performing the procedure has been trained to follow a logical sequence of steps, developed to maximize the knowledge gained from the procedure. He will proceed systematically, examining the body's tissues and organs, and taking the required samples.
The first step in the necropsy procedure is an external examination of the reptile's body. This will include an assessment of the animal's body condition, skin, mouth cavity, limbs and digits (if present) and an examination for external parasites. Any wounds, or abnormalities will be noted and measurements, such as length or weight may be taken. Relevant samples might include a biopsy of skin and any parasites to be identified. A culture of a wound or discharge might also be performed, to identify bacteria or fungus, where relevant. In some cases, a radiograph (X-ray) can provide useful information, even after death. Radiographs can reveal fractures or bone disease. Some foreign bodies, particularly those made of metal, can be seen on a radiograph. These may or may not be the immediate cause of death, but will be easier to locate, particularly in the case of larger animals, if the anatomic location can be pinpointed. Examples include coins and fish hooks.
Next the veterinarian will follow a sequence of steps as he opens the body cavity to examine internal organs. Most veterinarians, as a matter of training and habit, proceed in the same fashion each time a necropsy is performed. This makes it less likely that a step will be missed. First, the relative position of the organs is noted. This gives a clue as to whether an enlargement in one structure is pushing other organs out of their normal positions. The amount of fat in the body cavity and the muscle mass are assessed. This may shed light on the animal's nutritional state or the duration of disease. The organs are removed from the body cavity for further examination. The digestive tract is examined along its length, and foreign bodies or other blockages might be found at this time. The contents of the digestive tract may be submitted for further analysis. This might include testing for toxins (note that there is no one test which "checks for poison"- specific tests must be chosen, based on the toxin suspected). Samples taken from the contents of the digestive tract, or from the walls of the digestive tract may reveal parasites.
Cultures of bacteria are also commonly taken during the necropsy, not just from the gastrointestinal tract, but from any suspected sites of infection. The inside of a reptile's body is not necessarily a sterile place, and a culture of bacteria from within the body can help the veterinarian to determine if infection was the cause of death, or a secondary problem. This assessment is based on the type of bacteria, their location and their relative numbers.
Certain anatomical features are common to all animals and others are peculiar to reptiles or to a given group or species of reptile. For example, the kidneys of a snake are segmented and layered, in a flat, shingled sort of arrangement, and are located about 2/3 of the way down the body, one after the other. By contrast, the kidneys of the green iguana are more like a bean in shape and are normally located within the pelvis. Lungs and digestive tracts are also highly variable between groups of reptiles. Normal liver tissue is by and large similar in appearance to the naked eye. Given the vast range of normal and abnormal variation in the appearance of organs and tissues within one species, as well as between species of reptile, almost every necropsy will add to a veterinarian's knowledge base.
Regardless of the species, certain findings are always abnormal and can be seen without magnification: an enlarged heart, internal bleeding due to trauma, a blocked intestine leading to death of the digestive tract wall. It can be a mistake, however, to stop at the first sign of disease, and call it a diagnosis. White spots on the surface of the internal organs are often gout, and a swollen, pale liver often is shown to have excessive fat accumulation. An enlarged, abnormally textured ovary may be infected or cancerous, however, and certain bacterial and fungal infections can look very like cancer. Cancerous organs very commonly become infected. Even if one can with some experience make an educated guess at the nature of the disease process, it is never possible to be sure without further tests. All too often, our reptile patients have experienced more than one problem, and a complete necropsy lessens the chance that something will be missed.
During the gross post mortem, your reptile veterinarian will likely take samples. Most commonly these include skin, liver, kidney, gastrointestinal tract, spleen, ovary or testicle, pancreas, lung and heart. He may also sample muscle, brain or other nervous tissue, bone, bone marrow, bladder and reproductive tract. He may also take a sample of any discharge or foreign body, or tissue which he cannot identify. Samples may be processed in a variety of ways, depending on the nature of the sample and the disease process being investigated. In some cases a direct impression of the cut surface of the tissue, pressed on a glass slide leaves bacteria, parasites or distinctive cells, which may yield a diagnosis when processed and examined under the microscope.