Common lab tests for pets – Part 2

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Common lab tests for pets

Lab tests are an important part of your dog or cat’s routine checkups. Take a close-up look at some of the most common tests, and what they can tell you about your best friend’s health.

Whenever you take your dog or cat to the vet for a routine checkup, the veterinarian does various lab tests to look for potential health problems. It’s regular procedure, but have you ever wondered precisely what the vet is looking for, and what the results actually mean? In the first part of this article (see V19I3), we talked about some common blood tests for dogs and cats. Now we’ll focus on some additional testing that should be done, including urinalysis, fecal testing, radiography and ultrasonography.

1. Urinalysis

A urinalysis is typically done when you visit your own doctor, but most veterinarians do not routinely perform this important test. It may be because it’s harder to collect urine from animals, or because the doctors don’t appreciate the value of urine testing. Regardless, a urinalysis is an important adjunct to blood testing.

The urinalysis can complement results noted in blood tests, as well as give us additional information blood testing may not provide. For example, urine testing shows if glucose or ketones are present (indicating diabetes mellitus). A urinalysis can also detect early protein (albumin) loss through the kidneys, again not something a blood profile can do. Examining the urine microscopically also tells us about the possible presence of inflammation, infection, bleeding, cancer, and bladder stones. Whenever possible, your animal’s urine should be analyzed at least once every six months. A urine culture should also be done.

A urine culture 

Along with a urinalysis, a urine culture tells us two important things:

  1. if the animal has an infection of the kidneys or bladder;
  2. and which bacterium is causing the infection.

If bacteria are seen, they’re cultured and examined for susceptibility to antibiotic responsiveness.

I often see animals with “bladder infections/UTIs” diagnosed by other doctors, but who don’t actually have infections. The (mis)diagnosis occurred because it was based on a urinalysis without a culture. While a urinalysis may indicate a possible infection, only a culture can determine if an infection is present and if antibiotics are needed. In order to reduce the need for antibiotics and prevent further antibiotic resistance (many bladder issues are easily treated without them), a culture is a must before antibiotics are routinely used to treat possible UTIs. (Exceptions would include a animal that has heavy bleeding in his urine, or a urinary blockage in which an underlying infection is a likely cause.)

Another important note: if a dog or cat is treated with antibiotics for a UTI based on a culture, a follow-up culture should be done one to two weeks after finishing the antibiotics to make sure the bacteria are killed, thereby preventing a worse infection due to incorrect treatment.

2. Fecal testing

Healthy dogs and cats should be given a fecal test at least twice yearly, since they can harbor intestinal parasites, some of which may be transmitted to other animals and even people. Positive test results usually indicate the need for a de-worming, with follow-up testing to ensure all the parasites are killed.

Fecal testing is also done on animals with any illness, but especially GI illness that includes vomiting and diarrhea. Several tests can help diagnose the cause of GI signs:

  1. A microscopic fecal examination checks for intestinal parasites.
  2. I also like to do a fecal Gram’s stain to check for overgrowth of abnormal bacteria and yeasts.
  3. Occasionally, I will also do an ELISA test to look for the protozoan parasite Giardia.
  4. If these tests are normal but clinical signs are still present, I will send a fecal sample to one of my outside labs for a fecal PCR test. This newer test looks for the DNA of various parasites, bacteria and bacterial toxins.

Most causes of diarrhea and other GI problems can be diagnosed with repeated fecal testing

3. Radiography

Radiography involves using tiny amounts of X-ray radiation, allowing the doctor to look inside your dog or cat’s body. It is useful for any animal with any type of illness, but is typically used for orthopedic problems (fractures, dislocations) and soft tissue problems (bladder stones, GI obstructions, heart/lung disorders).

Radiography is excellent for the early diagnosis of animals who do not appear to have any specific problems; for example, puppies can be screened for possible hip dysplasia. In my practice, we do radiographs (at a discount) as a screening procedure when the animal is sedated or anesthetized for another procedure such as spaying, neutering and dental cleaning. We often find problems when radiography is done on these “normal” animals, allowing us to present treatment options before they develop serious problems.

We often find problems when radiography is done on “normal” animals, allowing us to present treatment options before they develop serious problems.

One note I want to make deals with two problems I routinely see when clients come in for a second opinion, and bring radiographs with them. First, with very rare exceptions, animals must be sedated in order to get proper positioning for a high-quality radiograph (sedation also minimizes exposure to radiation since fewer pictures are needed). Second, the proper number of radiographs must be taken in order to avoid misdiagnosis. In my practice, I typically take at least three views of the body part and/or the corresponding “normal” anatomy. Poor quality radiographs, or incorrect views or number of views, often mean I have to take even more radiographs.

4. Ultrasonography

I use ultrasonography for several reasons:

  • Whenever I hear a heart murmur during a physical exam, I need to do an echocardiogram (heart ultrasound) to determine the extent of heart disease.
  • If I suspect an internal tumor, I do an ultrasound to screen for cancer.
  • I’ll use ultrasonography any time I see an unexplained illness that isn’t diagnosed with the other tests I’ve discussed in both parts of this article, or if my screening test results for inflammation and cancer (TK, CRP, CRA) are elevated.

Ultrasound exams are safe as they use sound waves rather than radiation. They can usually be done without the need for sedation unless the animal is fractious. Because ultrasound technology images body tissue differently from radiographs, both tests are typically needed (usually starting with radiographs since they are easier and less expensive).

I’ll use ultrasonography any time I see an unexplained illness that isn’t diagnosed with other tests.

Ultrasound exams are also useful as screening tests. For example, Scottish terriers have a high incidence of bladder cancer, while larger dogs (especially retrievers) have a high incidence of cancer in the spleen and liver. I recommend these dogs have twice-yearly screening ultrasounds, beginning around five years of age, to screen for these serious and often fatal diseases.

I hope the two-part article has helped you understand the importance of common lab tests performed on both healthy and sick dogs and cats. By intelligently using these tests, you and your vet can extend your dog or cat’s life with an early diagnosis of health problems, allowing for a quick resolution of illness.