Acute Diarrhea

What is acute diarrhoea?

Acute diarrhoea is when there is an excessive abrupt amount of water within a pets feces for a period of less than approximately 5-7 days. The condition occurs when there are imbalance in mechanisms involved within the intestines. The condition is fairly common, but seen more in young cats and dogs.

Acute Diarrhea

What are the causes?

There are a large number of reasons why acute diarrhea can occur. Most cases are dietary-related issues whereby there may have been an abrupt change in diet, ingestion of foreign material or rotten food. Metabolic diseases such as liver, kidney or pancreatic disease can also cause acute diarrhea. Other causes include the presence of viral/bacterial/parasitic pathogens or ingestion of drugs and toxins.

Does a luxating patella cause any long-term problems for my dog?

This depends upon the grade of the luxation and whether both legs are affected to the same degree. Patellar luxations are graded from Grade I-IV. Some dogs can tolerate this condition for many years, even for their entire life.

However, patellar luxation predisposes the knee to other injuries, such as torn cruciate ligaments. The weight bearing stress on the leg is also altered, leading to changes in the hips, thigh, and shin bones. As the pet ages, arthritis develops and results in decreased mobility and joint pain.

Acute Diarrhea

What are the clinical signs?

Acute diarrhea often occurs as an isolated episode and may not affect the animal systemically. Clinical signs vary depending on disease severity.

Most animals will present with:

  • Change in fecal consistency or vomiting
  • Blood or mucous in stools
  • Reduced appetite.
  • Dehydration
  • Abdominal Pain
  • Weakness and lethargy.
  • +/- vomiting
Acute Diarrhea
Acute Diarrhea

What tests are involved?

Gathering a thorough history of the patient is the first step to evaluating acute onset diarrhoea. After a thorough history is attained the veterinarian will perform a physical examination whilst paying extra attention to the abdomen (e.g. assessing for pain, potential foreign body, abdominal sounds etc).

A veterinarian is like to recommend baseline bloodwork and fecal flotation (to rule out parasites). Additional tests may include abdominal radiographs and ultrasound. More advanced testing (e.g. malabsorption profiles, pancreatic testing, PCR testing for certain organisms/bacteria) may also be required if the pets condition cannot be entirely defined.

How is it treated?

Each condition is treated individually depending on the individual cause. Some cases can be managed with simple dietary management.

In mild cases the veterinarian may manage your pets condition as an outpatient with anti-diarrhoeals, pro-biotics, antibiotics and dietary management

In more serious cases however the veterinarian may recommend hospitalization, IV fluid therapy, antibiotics, analgesia and anti-emetics.

what are we testing for?

By definition, acute diarrhoea will resolve, with or without treatment, within two weeks. Diagnostic testing is therefore infrequently carried out. A study using data from the Small Animal Veterinary Surveillance Network (SAVSNET) reported that diagnostic tests were performed in only 16 percent of cases with diarrhoea that were seen in general practice. The most common tests performed were blood tests (haematology and biochemistry) and faecal analysis (parasitology and bacteriology). Another recent study reported that faecal analysis was carried out in 7.8 percent of dogs and 6.8 percent of cats presenting with diarrhoea. One author writing about the management of diarrhoea in cats recommended reserving faecal cultures for cats which develop sudden-onset, acute, bloody diarrhoea with evidence of sepsis; cats which develop diarrhoea after kennelling or shows; or when multiple cats from one household are affected. These seem reasonable considerations for faecal culture as they are situations more suggestive of potential bacterial infection, although viral, protozoal and parasitic infections should also be considered.

The aim of faecal analysis in cases of acute diarrhoea is to identify the presence of infectious agents to guide treatment or to provide prognostic information. There is no doubt that detection of parasites or protozoa will often indicate that certain treatments are required, or that isolation of certain viruses (eg parvovirus) will help the clinician to provide prognostic guidance for the owner. However, given that Salmonella, Campylobacter, Yersinia and E. coli O157 have all been isolated from healthy animals, detection of these bacteria in faecal samples does not necessarily confirm the cause of the diarrhoea. All of these bacteria are zoonotic, so testing may be indicated if there is concern regarding zoonotic disease within a household (eg presence of children, immunocompromised people or owners with significant symptoms themselves). However, as we will discuss in more detail in part two, the use of antibiotics solely to try to achieve elimination of these bacteria from the pet’s stool samples is questionable.


Part one of this two-part series investigated the potential causes for acute diarrhoea and how difficult it can be to ascertain whether isolation of potentially pathogenic bacteria, from the stools of dogs with acute diarrhoea, is of clinical relevance to an individual patient. Part two will address when and why antibiotics are currently prescribed for acute diarrhoea, whether they are truly indicated and the potential adverse effects of their use.

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