Much of what happens daily while delivering health care revolves around making a diagnosis. The process of arriving at a diagnosis directly impacts our pet companions and their care givers. Understanding what a diagnosis is and how it is obtained can significantly improve communication and understanding of recommended testing and therapy. A diagnosis is, in loose terms, a description of what is wrong. Sometimes arriving at a diagnosis is simple, and other times it is a complicated process filled with challenges.

An example of a simple diagnosis is a dog with a broken femur after an encounter with a car: The diagnosis is a fractured femur bone. The specific type and location of the fracture will be described as part of the diagnosis (i.e. a comminuted fracture). In this example, arriving at a diagnosis involves a stepwise process beginning with the history (dog was OK before the car), physical exam (swollen, unstable, painful leg) and radiographs of the leg (shows the broken bone). This stepwise assessment is important, because the radiograph shows the fracture but does not tell you that the cranial cruciate ligament (CCL) in the knee is also torn. Assessment of the CCL occurs during the physical exam.

Making a diagnosis in other situations can be more challenging, requiring more detective work. For example, a cat with chronic diarrhea has a long list of possible causes and diagnoses. Identifying the exact cause provides the diagnosis. The sidewise process again starts with a clear history. This history is important because diarrhea in cats is one of their most common problems and has so many causes. Some causes directly relate to the digestive tract, while others do not. 

The history, including lifestyle (i.e. indoors only, likes to eat house plants, multiple cats in the house, etc.), age (older cats generally have different problems than younger cats), appetite, how long the diarrhea has been occurring and if vomiting is also present. These historical observations help to provide focus for the diagnostic workup and can shorten the list of possible causes. This list can be further narrowed with the findings of the physical exam. For example, a cat with diarrhea that has been drinking lots of water, urinating frequently, has an increased appetite and weight loss could have a problem with the thyroid or diabetes mellitus (other causes are possible). The physical exam can identify the presence (or absence) of enlarged thyroids, which could point toward a diagnosis of hyperthyroidism. However, the absence of enlarged thyroids in the neck does not rule out hyperthyroidism, because the enlarged glands can slide into the chest.

Once the history and physical exam are completed, specific testing is often needed to finalize the diagnosis. In our example, a complete blood count, serum chemistry profile, urinalysis and T4 (thyroid test) are important. These tests can show if there is an increased glucose in the blood implying diabetes as the diagnosis. However, cats can increase their blood glucose to high levels when they are stressed (such as a car ride to the veterinarian), giving a false impression of diabetes. An additional test (fructosamine) may be needed, because this gives information on what the glucose was a couple of weeks before. Glucose present in the urine implies diabetes, but there are other causes. Also many diabetic cats have bladder infections, so the urine tests have multiple diagnostic uses.

What happens if all the initial tests come back in the normal range? Then additional evaluation becomes necessary. For a diarrhea problem, this could include abdominal radiographs and ultrasound, testing of the pancreas, evaluation for infectious causes or food allergies, and assessment for cancer or inflammatory bowel disease.

The body is a complex group of organs, glands and other tissues that interact to maintain a balance that we interpret as health. There is also a tremendous ability to cover up or compensate for problems. Because the cat is a master at not showing signs of illness, having a complete workup is essential for diagnosis.

If all this sounds complicated, it can be. This is why so much training is necessary for a veterinarian and why clear communication between the veterinarian and pet care giver is critical. Your veterinarian recommends tests that will guide them to a diagnosis. Without those tests, many problems cannot be adequately assessed or diagnosed.

Ron Carsten, DVM, PhD, CVA, CCRT was one of the first veterinarians in Colorado to use the integrative approach, has lectured widely to veterinarians, and has been a pioneer in the therapeutic use of food concentrates to manage clinical problems. He is also the founder of Colorado Animal Rescue (CARE). In addition to his Doctor of Veterinary Medicine, he holds a PhD in Cell and Molecular Biology and is a Certified Veterinary Acupuncturist and Certified Canine Rehabilitation Therapist. He practices integrative veterinary medicine in Glenwood Springs.