Diarrhea in Cats


Diarrhea is the occurrence of loose, watery stools caused by a gastrointestinal issue. This is a common symptom of a number of disorders in cats which varies in severity from harmless to deadly.

Diarrhea is separated broadly into large bowel and small bowel diarrhea. Among other characteristics, the former often presents with mucus in the stool and the latter with a decrease in appetite.

Diarrhea is characterized as either acute (symptoms came on suddenly and/or recently) or chronic (symptoms have been present long-term, usually for a minimum of two to three weeks).

Diarrhea is caused by a multitude of conditions including dietary factors, parasites, infections, endocrine and metabolic disorders, injury, toxins, and irritants.


Diarrhea varies in severity and the urgency of response to it will vary accordingly. The presence of blood in the diarrhea does not always indicate an emergency. Instead, the urgency of care is determined by the presence and severity of other symptoms.

Small bowel diarrhea: Diarrhea originating from the small intestines usually has the following characteristics:

• Mildly increased frequency • Increased volume • If present, blood appears black and tarry (melena)

• Excess flatulence

Large bowel diarrhea: Diarrhea originating from the colon typically presents with:

• Increased frequency • Straining (tenesmus) • Increased urgency • Decreased volume • Mucus present

• If blood is present, it is usually red (hematochezia)

Possible Causes

Diarrhea is caused by a number of factors which are categorized as follows:

Dietary: • Changing a diet, especially suddenly • Dietary indiscretion or food sensitivity

Parasitic: • Roundworms • HookwormsTapeworms

Infectious Diseases: • Bacterial • Viral• Protozoal

Inflammatory and auto-immune diseases: • Inflammatory bowel disease • Food allergies

Metabolic Diseases: • Liver disease • Kidney disease

Endocrine disorders: • Hyperthyroidism

Cancers: • Stomach cancer • Intestinal cancer • Pancreatic cancer • Lymphatic cancer

Trauma: • Tumors • Hernias • Intussusception • Foreign object in the intestinal tract

Toxic/Poisonous irritants: • Foods • Chemicals • Non-food biologics (plants/mushrooms)

Risk Factors

Most illnesses that cause small bowel diarrhea come on suddenly and show other symptoms like appetite loss, vomiting, and lethargy. Conditions causing large bowel diarrhea are more likely to be chronic and present with a history of weight loss.

If the cat is elderly, pregnant, otherwise chronically ill, or a kitten, it is advisable to reach out to a vet when diarrhea occurs as they are at higher risk of more serious complications.

Testing and Diagnosis

After medical history and physical examination, diagnostics for diarrhea typically include:

• Fecal analysis, including cytology and flotation to look for pathogens

• Blood work, including retrovirus testing, a complete blood count, serum chemistries, and thyroid levels

• Diagnostic imaging. Both x-rays and ultrasound may be used to provide information about the appearance of the digestive tract

Similar symptoms

While the appearance of diarrhea varies widely, it is not difficult to differentiate it from formed stools.

It is often difficult for pet parents to distinguish if a cat straining in the litter box is struggling to defecate or urinate.

Associated Symptoms

Other symptoms often observed alongside diarrhea include;

• Dehydration • Weight loss • Loss of appetite • LethargyVomiting

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