Diarrhea in Cats

Diarrhea is defined as an increase in the liquidity of stools.

How is diarrhea classified?

​Pathophysiology classification:

• Osmotic diarrhea: Caused by an increase in the amount of unabsorbed and osmotically active solutes.  This type of diarrhea can occur when food is not digested properly.

• Secretory diarrhea: Caused by excessive secretion of fluid into the gut.  This type of diarrhea can be caused by enterotoxigenic bacteria, parasitic disease, and inflammatory disease such as IBD

• Altered permeability diarrhea: Caused by disruption of the integrity of the intestinal mucosa (lining) or ulceration leading to a loss of blood, proteins, etc. into the gut.  This type of diarrhea can be caused by severe inflammation (such as IBD), lymphoma/cancer, and NSAID treatment.

• Altered motility diarrhea: Increased peristalsis can lead to diarrhea; however, this is rarely a primary cause.

Classification by source:

• Large bowel diarrhea: Hallmarked by decreased or normal volume but a markedly increased frequency of defecation.  Straining is often present.  Stools can contain mucous and may show signs of fresh blood. Weight loss is not common.

• Small bowel diarrhea: Hallmarked by increases in both volume and frequency of defecation.  Straining is generally absent.  There is minimal mucous and blood, if present, is dark and tarry in appearance.  Weight loss is common.

What are the causes of diarrhea in cats?

There are many diseases, both within the GI system and outside of it, in which diarrhea is a symptom.  Some causes are more common in kittens whereas other causes are generally associated with older cats.  A brief list of possible causes can include:

Primary gastrointestinal

• Food allergy
• Food intolerance
• Infectious diseases including Salmonella, Campylobacter, and E.coli
• Inflammatory bowel disease (IBD)
• Cancer
• Non-specific inflammation
• Parasites including nematodes, Giardia, Tritrichomonas, Cryptosopridium, Isospora/Coccidia

Extra-gastrointestinal (i.e. systemic disease that have vomiting as a symptom)

• Exocrine pancreatic insufficiency
• Cancer
• FIV and/or FeLV
• Liver disease
• Hyperthyroidism
• Renal failure

How is diarrhea diagnosed?

Note: If your cat is being seen for diarrhea then it is essential that you bring in a fresh stool sample with you at the time of your appointment.

​As diarrhea has many possible causes, there are several steps in diagnosing a cause.

• History: Important history can include when did the diarrhea start, what the diarrhea looks like (i.e. is there mucous or blood), frequency of defecation, signs of straining, recent changes in diet, exposure to plants or a history of getting into garbage.  Other information such as additional changes (i.e. changes in water intake or weight loss) may help in cases of systemic illness.  Age of the patient as well as any previous treatment can be useful in determining where to start

• Physical exam will look for signs of systemic disease as well as assess the overall health of the kitty 

• Lab work:
  • If parasites are suspected, than a fecal analysis may be run.
  • As bacteria and viruses cannot be identified under the microscope and some parasites, such as Tritrichomonas, do not do well outside the host body or, like Cryptosporidum, are very small to see if fecal samples then newer lab tests are available that look for parasite/infectious disease DNA and RNA in a fecal sample to diagnose these infectious agents.
  • Stool culture can be done to identify pathogenic bacteria such as Salmonella
  • Basic blood work and urine analysis can be run to look for signs of systemic illness, including changes in liver enzymes and pancreatic digestive enzymes.  In older cats, this blood work with include a check of thyroid hormones to rule out hyperthyroidism.  If pancreatic insufficiency is suspected, then additional blood work such as checking enzyme levels may be required
  • FIV, FeLV screening is a must in all cats.

What are the treatment options for diarrhea?

Treatment will depend on the underlying causes of the diarrhea but can include diet change, deworming, antibiotics, etc.