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Many different diseases and disorders can cause diarrhea in pets. It can be as simple as a pet having intestinal parasites (worms) or eating spoiled food. However, in many cases, the cause is more difficult to determine. The following are just a few of the many causes of diarrhea:
Diagnosis starts with a complete history and physical examination. A pet’s history is the information you give your veterinarian about your pet’s illness, including details about the frequency, urgency, and appearance of the diarrhea.
Other helpful information includes whether your pet has eaten anything unusual, such as house plants or table scraps, or whether the pet is showing other signs of illness such as weight loss, poor appetite, or vomiting. To help you put this history together before visiting your veterinarian, please see the handout "Diarrhea Questionnaire and Checklist".
A physical examination involves checking out all parts of the body and may give clues about the cause of diarrhea. For example, a lethargic puppy with a fever and bloody diarrhea may have a parvovirus infection, a cat with thickened bowels may have intestinal cancer, and a dog in good body condition that frequently passes small amounts of diarrhea may have colitis (inflammation of the lower bowel).
Sometimes, a diagnosis can be made based on history and physical examination, but in most cases, additional diagnostic tests will be needed. Your veterinarian may recommend basic screening tests that provide information about your pet's overall health and may provide further clues about the underlying problem.
The most commonly recommended screening tests for a pet with diarrhea include a complete blood count (CBC), serum biochemistry profile, urinalysis, and fecal parasite tests. Thyroxine (total T4) concentration is also recommended for middle-aged to older cats. Screening tests may provide clues to the cause of the diarrhea. In addition, they may uncover problems caused by diarrhea, such as electrolyte disturbances and dehydration.
Complete Blood Count (CBC) is a simple blood test that provides information about the different cell types in blood. These include red blood cells, which carry oxygen to the tissues, white blood cells, which fight infection and respond to inflammation, and platelets, which help the blood clot. The CBC provides details about the number, size, and shape of the various cell types and identifies the presence of abnormal cells in circulation (see handout “Complete Blood Count”).
In a pet with diarrhea, some changes that could be seen on a CBC include:
Serum biochemistry profile looks at many substances, including proteins, enzymes, fats, sugars, hormones, and electrolytes. Measuring the levels of the various substances in the blood provides information about the health of the body’s organs and tissues, such as the liver, kidney, and pancreas. Changes and abnormalities found in the biochemistry profile can help diagnose various diseases and disorders (see handout “Serum Biochemistry”).
In a pet with diarrhea, some changes that could be seen on a serum biochemistry profile include:
Urinalysis is a simple test that analyses urine's physical and chemical composition. It measures how well the kidneys are working, identifies inflammation and infection in the urinary system, and helps to detect diabetes and other metabolic disturbances. Urinalysis is essential for adequately interpreting the serum biochemistry profile and should be done at the same time as blood testing.
In a pet with diarrhea, some changes that could be seen on a urinalysis include:
Testing for intestinal parasites that can cause diarrhea, especially in puppies and kittens. No test can detect all intestinal parasites, and several different tests may be used. The most straightforward test is fecal flotation, in which a small amount of fresh stool is prepared and examined microscopically for the presence of parasites or parasite eggs. Multiple fecal flotations may be needed to detect infection. A simple version of the fecal flotation can be done in the veterinary clinic, or a sample can be sent to the laboratory for a more sensitive test that also screens for parasite DNA.
Some intestinal parasites, such as Cryptosporidium, Toxoplasma, Giardia, and Tritrichomonas, are challenging to detect with flotation methods. Specialized testing, including blood tests, may need to be done. Samples may be sent to a veterinary referral laboratory for these tests.
Serum thyroxine (total T4) is used to diagnose hyperthyroidism in cats. Hyperthyroidism is caused by an overactive thyroid gland and is common in middle-aged to older cats. The gland produces excessive thyroid hormones, substantially increasing the body’s metabolic rate and often causes vomiting and diarrhea.
If your pet is bright and alert and the physical examination is normal, screening tests may not be immediately recommended. This is especially true if there is an obvious reason for the diarrhea, such as a sudden change in diet or a history of eating table scraps. However, screening tests are strongly recommended if diarrhea continues or reoccurs or your pet shows other signs of illness, such as fever or abdominal pain.
Depending on the results of a pet’s history, physical examination, and screening tests, many additional tests might be recommended. If the diarrhea seems to be caused by problems that do not involve the gastrointestinal tract, such as liver disease, kidney failure, Addison’s disease, or heart disease, specific testing for those conditions would be recommended.
If screening tests suggest the problem involves only the gastrointestinal tract, further testing will focus on stomach and bowel disorders. Some examples of testing that might be recommended include:
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2611 Route 52 Hopewell Junction, NY 12533
(845) 221-PETS (7387) info@hopewellanimalhospital.com
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