Clinical Pathology and Procedures

Collection and Submission of Laboratory Samples

Each veterinary diagnostic laboratory offers a unique set of diagnostic tests that is subject to frequent changes as better tests become available. The increasing availability of tests based on newer molecular biology techniques is an excellent example of this trend. The protocols for sample collection and submission are therefore also subject to change. The practitioner and diagnostic laboratory staff must maintain good communication to complete their diagnostic efforts efficiently and provide optimal service to the client. Practitioners must be specific and clear in their test requests. The laboratory staff can provide guidance when there are questions regarding sample collection and handling, as well as offering assistance in interpretation of test results. Most diagnostic laboratories publish user guidelines with preferred protocols for sample collection and submission, but the following broad recommendations are fairly standard.

Diagnostic Imaging

Radiography comprises the majority of diagnostic medical images generated in veterinary practice, but other imaging modalities such as ultrasonography, CT, MRI, and nuclear imaging are also very important and commonly available in specialty practices and academic centers. Imaging provides a large amount of information by noninvasive means. It does not alter the disease process or cause unacceptable discomfort to the animal. Although radiography itself is painless, sedation is often desirable to reduce anxiety and stress associated with the procedure, to promote acquisition of good diagnostic studies with minimal repeats, and to control pain associated with manipulation in animals with painful disorders such as fractures and arthritis.

Diagnostic Procedures for the Private Practice Laboratory

Numerous laboratory tests can be done in a private practice laboratory. Use of a commercial laboratory versus in-house testing should be evaluated to determine whether in-house testing is practical and economical. Because the availability of diagnostic laboratories and their reporting intervals may be problematic (eg, nights and holidays), performing some diagnostic screening tests in-house is often desirable. However, because the people performing these tests often have minimal technical training, quality control procedures must be rigorous. The time and care that must be devoted to quality control issues may preclude in-house testing in many practices. Errors may occur not only in testing procedures but also in sample collection and handling and in recording results.

Disposal of Carcasses and Disinfection of Premises

When animals die or are slaughtered on farms, carcasses and parts that are unfit for use as food should be disposed of properly. Safe and environmentally responsible disposal of animal carcasses, whether an individual death or during significant mortality events, is an essential consideration. Premises should be promptly cleaned in a manner that prevents any infectious or toxic health hazard to domestic or wild animals or people. Information on the safe and lawful disposal of carcasses can be obtained from local environmental protection agencies. When the circumstances under which death has occurred suggest a transmissible disease or toxic hazard, the nearest animal health official should be notified immediately.

Euthanasia

Euthanasia is the term used to describe ending the life of an animal in a way that eliminates or minimizes pain and distress. Animal slaughter, depopulation, and humane killing are distinguished from euthanasia, because they are performed for reasons different than sparing an animal from unresolvable painful or distressful conditions. Euthanasia of animals is a common procedure performed by veterinary professionals, and because of the seriousness of the action, it deserves appropriate consideration. Some of the most difficult euthanasia decisions that veterinarians are required to make involve the euthanasia of healthy animals when no other alternative for their care can be identified. A veterinarian must be fully prepared to speak frankly about the animal’s condition and be knowledgeable about all possible alternative care resources when interacting with animal owners, caretakers, and control professionals. Recognizing the importance of a "good death" in the humane termination of an animal’s life, many countries and professional organizations have developed guidelines and recommendations for animal euthanasia; some are more specific for certain species and environmental settings. Most recommendations emphasize certain factors that personnel performing euthanasia should consider when selecting the best method of euthanasia. These factors include: 1) ability of the method to induce loss of consciousness and death with minimal pain and distress; 2) time required to induce loss of consciousness; 3) reliability; 4) safety of personnel; 5) irreversibility; 6) compatibility with intended animal use and purpose; 7) documented emotional effect on observers or operators; 8) compatibility with subsequent evaluation, examination, or use of tissue; 9) drug availability and human abuse potential; 10) compatibility with species, age, and health status; 11) ability to maintain equipment in proper working order; 12) safety for predators or scavengers should the animal’s remains be consumed; 13) legal requirements; and (14) environmental impacts of the method or disposition of the animal’s remains.

Meat Inspection

Inspection of meat by qualified individuals to eliminate unwholesome, adulterated, or mislabeled meat or meat products from the food supply protects consumers from the physical, infectious, and toxic hazards that may originate in food animals, the environment, or people. The standard procedures do not cover every possibility concerning the acceptability of carcasses, organs, or other animal parts; personal judgment is also required to ensure that only wholesome, unadulterated product is approved for food. (Also see Chemical Residues in Food and Fiber.)

Prepurchase Examination of Horses

Also see The Lameness Examination in Horses.

Prepurchase Examination of Ruminants and Swine

Also see Biosecurity.

Radiation Therapy

Radiation therapy has seen dramatic increases in demand and sophistication in recent years, which has led to creation of a board specialty in radiation oncology, granted by the American College of Veterinary Radiology. The sophistication and scope of both veterinary imaging and radiation therapy has advanced to the point that only a few radiologists now actively practice in both the fields of imaging and therapy.

Veterinary Manual