Chronic Diarrhea in Cats

Chronic Diarrhea in Cats – Overview

  • A change in the frequency, consistency, and volume of bowel movement (feces) for more than 3 weeks or with a pattern of episodic recurrence
  • Can be either small bowel (small intestine) or large bowel (large intestine or colon) diarrhea

Signs/Observed Changes in the Pet

  • Underlying disease process determines clinical signs

Small Bowel Diarrhea (Involves the Small Intestines)

  • Larger volume of bowel movement (feces) than normal
  • Frequency of defecation is mild to moderately above normal (2–4 times per day)
  • Weight loss
  • Increased appetite (known as “polyphagia”) in cases with abnormal digestion or absorption of food (known as “maldigestion” or “malabsorption,” respectively) or increased levels of thyroid hormone (known as “hyperthyroidism”)
  • May have black, tarry stools (due to the presence of digested blood; condition known as “melena”); no mucus or red blood in the bowel movement (presence of red blood in the bowel movement known as “hematochezia”)
  • Little to no evidence of painful defecation or straining to defecate (known as “tenesmus”) or difficulty in defecating (known as “dyschezia”)
  • May have excessive gas formation in the stomach or intestines (known as “flatulence”) and rumbling or gurgling sounds caused by movement of gas in the intestinal tract (known as “borborygmus”)
  • Vomiting—variable
  • Poor body condition with some causes of long-term (chronic) diarrhea
  • Dehydration—variable
  • Thickened intestines, abdominal fluid, and enlarged abdominal lymph nodes may be felt by your pet’s veterinarian

Large Bowel Diarrhea (Involves the Large Intestines or Colon)

  • Smaller volume of bowel movement (feces) per defecation than normal
  • Frequency of defecation significantly higher than normal (greater than 4 times per day)
  • No weight loss
  • Often mucus or red blood in the bowel movement (hematochezia); no evidence of black, tarry stools (melena)
  • Painful defecation or straining to defecate (tenesmus) and urgency to defecate
  • Difficulty defecating (dyschezia) with rectal or lower colonic disease
  • Excessive gas formation in the stomach or intestines (known as “flatulence”) and rumbling or gurgling sounds caused by movement of gas in the intestinal tract (known as “borborygmus”)—variable
  • Vomiting—variable
  • Body condition more typically normal
  • Dehydration—uncommon
  • Thickened intestines may be felt by your pet’s veterinarian


  • Inflammatory bowel disease (IBD)—various types, including lymphoplasmacytic enterocolitis, granulomatous enteritis, eosinophilic enteritis/hypereosinophilic syndrome, and idiopathic inflammatory colitis
  • Tumor or cancer—lymphoma, adenocarcinoma, mast cell tumor, and polyps
  • Blockage or obstruction of the small or large intestines—tumor or cancer, foreign body, IBD, folding of one segment of the intestine into another segment (known as “intussusception”), and abnormal narrowing of the intestines (known as a “stricture”)
  • Metabolic disorders—increased levels of thyroid hormone (known as “hyperthyroidism”), kidney disease, liver disease, diabetes mellitus (“sugar diabetes”)
  • Poisons
  • Side effect of medications
  • Parasites—Giardia, Toxoplasma, roundworms (Toxocara cati, Toxascaris leonina), hookworms (Ancylostoma), Cryptosporidium, Cystoisospora, Tritrichomonas
  • Bacterial infections—Escherichia coli, Campylobacter, Salmonella, Yersinia, and Clostridium perfringens
  • Viral infections—feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), and feline infectious peritonitis (FIP)
  • Fungal diseases—histoplasmosis, aspergillosis
  • Non-inflammatory causes of abnormal absorption of food (malabsorption)—dilation of the lymphatic vessels (known as “lymphangiectasia”); condition in which a high number of bacteria are found in the upper small intestine (known as “small intestinal bacterial overgrowth”); diarrhea and other signs caused by absence of a long section of small intestine, usually because of surgical removal (condition known as “short-bowel syndrome”); and ulcers in the upper small intestines (known as “duodenal ulcers”)
  • Abnormal digestion of food (maldigestion)—liver disease and syndrome caused by inadequate production and secretion of digestive enzymes by the pancreas (known as “exocrine pancreatic insufficiency”)
  • Diet—dietary sensitivity, dietary indiscretion (that is, eating substances that should not be eaten), and diet changes
  • Congenital (present at birth) anomalies—short colon; condition in which blood vessels allow blood to flow abnormally between the portal vein (vein that normally carries blood from the digestive organs to the liver) and the body circulation without first going through the liver (known as a “portosystemic shunt”)

Risk Factors

  • Dietary changes and feeding poorly digestible or high-fat diet

Health Care

  • Often must be specific for the underlying cause to be successful
  • When no definitive diagnosis is possible, treatment with dietary management and metronidazole sometimes results in clinical improvement
  • Fluid therapy for dehydration
  • Correct electrolyte (such as sodium, potassium, chloride) and acid–base imbalances


  • A lower-fat, novel protein and carbohydrate (a protein and carbohydrate to which the pet has never been exposed) diet or fiber-supplemented diet may be beneficial; feed for 3–4 weeks; may resolve diarrhea due to dietary intolerance or allergy
  • Food should be highly digestible


  • Biopsy of the stomach, small intestine, and/or large intestine
  • Exploratory surgery of the abdomen and surgical biopsy


  • Medications presented in this section are intended to provide general information about possible treatment. The treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive
  • Medications vary, depending on underlying cause

Follow-Up Care
Patient Monitoring

  • Fecal volume and character, frequency of defecation, and body weight
  • Recheck for intestinal parasites

Preventions and Avoidance

  • Depend on underlying cause

Possible Complications

  • Dehydration
  • Poor body condition
  • Fluid buildup in the abdomen (known as “abdominal effusion”) with intestinal cancer (adenocarcinoma)

Expected Course and Prognosis

  • Depend on underlying cause
  • Resolution usually occurs gradually with treatment; if diarrhea does not resolve, consider re-evaluating the diagnosis

Key Points

  • Complete resolution of signs is not always possible, despite a correct diagnosis and proper treatment
  • Some causes of long-term (chronic) diarrhea result in actual changes to the lining of the intestines that may require many months to resolve or that may not resolve.

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