digestive system: diarrhea

The Classic Comprehensive Handbook of Cat Care


Diarrhea is the passage of abnormally soft and/or frequent stools. This sign is often associated with vomiting, but may also occur by itself.
When present, diarrhea often causes cats to fail to use their litter pans.


Diarrhea has many causes; the most common are related to diet. Diets containing cows’ milk often cause diarrhea. Spicy table scraps and decomposed food are other common offenders, but any food, including commonly fed commercial diets, can cause diarrhea in certain cats.

Viruses, bacteria, and intestinal parasites (e.g., worms, coccidia) may infect the bowel and cause diarrhea. This occurs most often in kittens.
Diarrhea can also be caused by diseases of the liver and/or pancreas, bowel obstruction, cancer, and metabolic problems. Even psychological stress gives some cats diarrhea. Trips to the veterinary hospital or the addition of a new cat to the household may result in stress-induced diarrhea, but this type usually subsides quickly without any treatment being required.

Inflammatory bowel disease (IBD) is also frequently accompanied by diarrhea. In this disorder, various types of blood cells that become active during bowel inflammation infiltrate the small intestine and/or colon and/or the stomach causing chronic dysfunction of the gastrointestinal tract. Unlike other causes of diarrhea, in IBD the veterinarian is not usually able to identify any specific agent that triggers the inflammatory process.

However, food allergies are not uncommonly involved. Vomiting is one of the frequent signs of inflammatory bowel disease in cats, but diarrhea is also a common sign that may occur by itself or accompany the vomiting.

When the large intestine (colon) is involved the affected cat may pass soft bowel movements containing excessive mucous and fresh blood. Left untreated diarrhea associated with inflammatory bowel disease can result in permanent damage to the bowel and an increased incidence of bowel cancer.