Testing for Vomiting

By Ryan Llera, BSc, DVM; Krista Williams, BSc, DVM; Kristiina Ruotsalo, DVM, DVSc, Dip ACVP & Margo S. Tant BSc, DVM, DVSc

What causes vomiting in a pet?

Many different diseases and conditions cause vomiting. Sometimes the cause is obvious, such as the pet that starts to vomit after getting into the kitchen garbage. The diagnosis would be upset stomach or gastritis due to dietary indiscretion (eating inappropriate things). However, the cause of the vomiting is not so clear in many cases.

Here is a list of just some of the many causes of vomiting:

  • Disorders of the gastrointestinal tract (stomach and bowel), including inflammation, bacterial or viral infections, parasites, tumors, dietary indiscretion, pancreatitis, constipation, and blocked bowel due to eating inedible material such as corn cobs, bones, socks (dogs), or string (cats)
  • Endocrine (hormonal) diseases, such as severe uncontrolled diabetes mellitus, hyperthyroidism in cats (overactive thyroid gland), and hypoadrenocorticism (Addison's disease 
  • Systemic diseases that affect the whole body, such as kidney failure, liver disease, pancreatitis, and serious bacterial infections (septicemia).
  • Miscellaneous conditions, such as motion sickness, neurological disorders, heatstroke, pain, fever, and eating toxic or poisonous material.

How can the cause of vomiting be determined?

Determining a 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. In a vomiting pet, this includes details such as how long the vomiting has been going on, whether your pet has eaten anything unusual (plants, garbage, table scraps), and whether your pet is feeling poorly or is bright and alert. This information can be beneficial; a vomiting cat with a history of playing with string may have an intestinal blockage from eating string, a large breed dog with a history of vomiting after eating may have a bloated or twisted stomach, and a normal active puppy may be vomiting because of intestinal parasites.

"Determining a diagnosis starts with a complete history and physical examination."

A physical examination involves looking at all parts of the body, listening to the heart and lungs with a stethoscope, and palpating the abdomen (gently squeezing or prodding the abdomen with the fingertips to assess the internal organs). A complete physical examination may give clues about the cause of vomiting. For example, a tense painful abdomen could be a sign of pancreatitis, a large amount of hard stool in the lower abdomen could indicate constipation, a fever might indicate an underlying infection, and an abdominal mass could be a tumor.

Sometimes, a diagnosis can be made just with history and physical examination; however, 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 often provide further clues about the underlying problem.

What screening tests are recommended, and why?

The most common screening tests for a vomiting pet include a complete blood count (CBC), serum biochemistry profile, and urinalysis. Other screening tests might include a fecal flotation for intestinal parasites, especially in puppies and kittens, and a serum thyroxine (total T4) test in middle-aged and older cats. Screening tests will likely provide clues to the cause of the vomiting. In addition, they may uncover problems caused by vomiting, such as electrolyte disturbances and dehydration.

"The most common screening tests for a vomiting pet include a complete blood count (CBC), serum biochemistry profile, and urinalysis."

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 in a vomiting pet might show elevations or decreases in red and white blood cells, which may help target the problem or area of the body causing the vomiting.

Serum biochemistry profile refers to the chemical analysis of serum, the pale, yellow liquid part of blood that remains after the cells and clotting factors have been removed. There are many substances in serum, 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. In a vomiting pet, a serum biochemistry profile might show changes affecting the kidneys, liver, blood glucose, pancreas, or electrolytes which can further guide your vet in determining the underlying cause or severity of the condition.

Urinalysis reveals the physical and chemical composition of urine. It measures how well the kidneys are working, identifies inflammation and infection in the urinary system, and helps detect diabetes and other metabolic disturbances. Urinalysis is necessary for adequately interpreting the serum biochemistry profile and should be done at the same time as blood testing. In a vomiting pet, changes that could be seen on a urinalysis include changes in the concentration, the presence of white blood cells, high levels of glucose and ketones (seen with diabetes), or bilirubin (seen with liver disease).

Testing for internal parasites that can cause vomiting, especially in kittens and puppies, may be performed. The most straightforward test for intestinal parasites is a fecal flotation, in which a small amount of fresh stool is prepared and examined microscopically for the presence of parasite eggs. 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 slightly better test that uses a concentration technique.

Serum thyroxine (total T4) can diagnose hyperthyroidism in cats. Hyperthyroidism is a common disorder in middle-aged to older cats and is caused by an overactive thyroid gland. The gland produces excessive thyroid hormones, substantially increasing the body’s metabolic rate and often causing vomiting and diarrhea. Most cases can be diagnosed with a single blood test measuring the total thyroxine level in the bloodstream. Affected cats typically have markedly elevated levels of T4 in their blood.

Do all these tests need to be done if my pet is vomiting?

No. If your pet is bright and alert and everything seems normal on physical examination, your veterinarian may delay testing. This is especially true if the vomiting seems to be an isolated event or the cause seems obvious, such as dietary indiscretion. However, suppose the vomiting does not clear up with treatment; if the vomiting recurs, or your pet is clearly unwell and showing signs of fever, lethargy, or painful abdomen, screening tests are strongly recommended.

What additional tests might be recommended for a vomiting pet?

Depending on the results of your pet’s history, physical examination, and screening tests, many additional tests might be recommended.

If screening tests suggest the vomiting is part of a systemic disease, such as liver or kidney disease, hypoadrenocorticism, or ketoacidosis (uncontrolled diabetes), additional testing specific to those diseases will be recommended.

If screening tests suggest the problem involves only the gastrointestinal tract, further tests to examine the stomach and intestines will be recommended, including:

  • Radiographs (X-rays), including a barium study (a series that shows how material moves through the stomach and intestines); sometimes radiographs will be done before other screening tests if something is felt during the exam.
  • Elimination diet trials to find out if there is a food hypersensitivity (allergy)
  • Ultrasound
  • Endoscopy
  • Exploratory surgery
  • Biopsy samples, often collected during an ultrasound, endoscopy, or exploratory surgery may provide a definitive diagnosis.
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