Diarrhea (Long-term) in Cats

Chronic Diarrhea in Cats

Feline chronic diarrhea is defined as a change in the frequency, consistency, and volume of feces for three weeks or with recurrence. The cause of diarrhea may originate in either the large or small intestine.

Symptoms and Types

Symptoms vary depending on the cause and origin. If diarrhea originates in the small intestine, symptoms include:

  • Unusual volume of feces
  • Weight loss
  • Abnormally frequent defecation
  • Black tar-like feces (melena)
  • Vomiting 

Symptoms due to diarrhea originating in the large intestine include:

  • Smaller volume of feces than usual
  • Abnormally frequent defecation
  • Mucus-like substances in feces
  • Vomiting


Chronic diarrhea may stem from a number of causes, including:

  • Irritable bowel disorder
  • Tumors
  • Parasites
  • Exposure to toxic materials
  • Birth abnormalities such as a short colon
  • Dietary sensitivity

Risk factors include:

  • Dietary changes
  • Difficult-to-digest or high-fat diet


A characteristic history based on the symptoms is first used to determine if the diarrhea is stemming from the small or large intestine. A number of additional medical tests may be used to pinpoint the exact cause.

Tests for digestive, metabolic, parasitic, dietary, and infectious causes are given. These include urine tests, fecal examination, analysis of rectal scrapings (which may reveal specific organisms or parasites), x-rays, and thyroid function tests. The thyroid regulates a number of metabolic processes, and diarrhea may stem from hyperthyroidism, a condition caused by overproduction of thyroid hormones.

If these possibilities are excluded, a test where a small, lighted device led through the mouth to the stomach (endoscopy), may be performed to search for irregularities. The procedure concentrates on the protective mucus lining of the stomach and the tube connecting the stomach to part of the small intestine (duodenum). A biopsy is taken during this procedure. A colonoscopy, in which a similar device is inserted into the rectum, may also be done in order to examine the entire colon for abnormalities.

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