Cat & Dog - Diarrhoea and Vomiting Tests

Do diagnostic tests help?

Diarrhoea and vomiting are common in our pets and can be due to many causes.  It is only as a result of careful history taking combined with a thorough clinical examination, including laboratory examination of samples, that the cause can sometimes be pinpointed.  Some causes are very obvious, such as dietary indiscretion, the dog that has raided the rubbish sack suddenly starts with vomiting and diarrhoea.  Similarly a puppy with diarrhoea containing worms obviously has a problem due to the worms.  Unfortunately the underlying cause is often not so obvious.

Intestinal causes

Vomiting and diarrhoea can be related to gastro-intestinal inflammation due to bacterial or viral infections, parasites, or ingested foreign material.  In addition vomiting alone can be due to a twisted or obstructed bowel or an internal blockage.

Diarrhoea without vomiting can be due to conditions such as maldigestion or malabsorption of food.

Non-intestinal causes

Both vomiting and diarrhoea can be due to non-intestinal causes such as endocrine (hormone) problems, e.g. sugar diabetes and kidney disease, as well as upsets due to certain drugs and toxins.

Vomiting can be associated with systemic diseases such as chronic kidney failure, liver disease and pancreatitis.

How is the cause determined?

1. Some diseases are more common in certain species (i.e. dog or cat) or breeds, or within certain age groups (i.e. puppies and kittens compared with adults). This can narrow down the range of possibilities.
2. Careful history including details of any medications or supplements that your pet has received or may have had access to can provide useful clues.  
3. Physical examination may also yield further clues which will then lead us to decide which screening tests are necessary.

Are any of these tests carried out routinely?

This depends upon each individual case.  A young dog with sudden vomiting and diarrhoea following known rubbish eating is unlikely to be subjected to a full blood test immediately.  If the condition has not improved following simple treatment for 24-48 hours then routine blood tests are indicated. See handouts on Routine blood tests and Routine laboratory tests 1 and Routine laboratory tests 2.

In addition to the standard blood and urine tests, faeces analysis for worms or other intestinal parasites is useful.  More specific tests depend on the individual case.  For example, in middle aged or older cats thyroid function tests (T4) are often very useful, particularly if there is recurrent vomiting.

What do standard screening tests usually reveal?

Complete Blood Count (CBC)

This gives an indication of the red blood cells, white blood cells and platelets.  The total number of cells together with specific cellular characteristics are recorded.  In addition, other parameters will indicate if dehydration is an issue.  Any blood loss will be indicated even if not visible in either the vomit or diarrhoea.

An elevated white blood cell count may suggest inflammation or infection.  Some conditions may be accompanied by increases in specific white blood cell types.  Thus an increase in eosinophils is often noted in cases of parasite problems or food allergies, and white cell numbers are reduced with some viral infections.

Serum biochemistry

Serum is the liquid part of the blood. The analysis of serum allows us to measure a whole range of substances, such as carbohydrates, fats, proteins.  Waste products (e.g. creatanine and urea) can indicate kidney inefficiency causing vomiting and/or diarrhoea.  Certain liver enzymes also give an indication of hepatitic efficiency.

Urine analysis

A urine analysis conducted on a sample obtained at the same time as the blood sample can be useful.  If the serum reveals increased blood urea nitrogen (BUN) and creatinine values, and the urine analysis indicates very dilute urine, it is possible that the vomiting and/or diarrhoea are due to chronic kidney failure.

On the other hand, if serum biochemistry and creatinine levels are elevated but urine is concentrated, this indicates dehydration and treatment will be entirely different.

Routine urine tests will also show the presence of red and white blood cells, glucose, protein and bilirubin (a pigment often associated with liver problems).  The presence of glucose in the urine sample accompanied by increased serum glucose indicates diabetes mellitus (sugar diabetes).

Faecal tests will pick up the common endoparasites (such as roundworms, tapeworms, hookworms, etc.) and microscopic organisms (such as coccidia or Giardia) which could be the underlying problem, particularly in cases of recurrent diarrhoea.

What further tests could be required?

This depends upon the individual animal and the results of the screening test.  In the majority of cases the screening test will either provide a specific diagnosis or show that further investigation is needed.

What further investigation is likely to be involved?

This depends entirely on the circumstances.  For example, T4 tests may be appropriate in the case of middle aged or older cats.  In the case of hypoadrenocorticism, if Addison's disease is suspected, specialised tests will be required to confirm the problem.

A dog or cat suffering from chronic recurrent diarrhoea may be suffering from exocrine pancreatic insufficiency (EPI) and special tests (TLI) may have to be performed.  Occasionally diagnostic imaging (x-rays, ultrasound, etc.) may be required.  Sometimes contrast radiology or exploratory surgery may have to be undertaken.

We will be happy to discuss any concerns.