Jeff Kahler: What could blood in cat’s stool mean?

Angela shares an apartment with her 6-year-old cat Andy. Andy has spent all his life indoors. Recently, Angela has noticed small amounts of blood in his stool. The stool is otherwise normal. It does not seem to show blood on every bowel movement but it has become increasingly prevalent. His diet consists of Science Diet Feline Maintenance in a dry form with occasional wet food of the same brand.

Visible blood in feces is usually the result of irritation to the colon. The colon is the large intestine at the end of the digestive tract and when it becomes irritated, it can bleed. There is a possibility that the stool can become bloody if there is a wound around the rectal area or a problem with one of the anal glands causing some bleeding. I am betting on the colon as the source.

The colon has the primary job of resorbing water from the stool. This is one of many mechanisms in a cat’s body to keep from wasting water. There is really no digestion of food done in the colon. Digestion of food and absorption of nutrients occurs primarily in the small intestine. After the small intestine does its job, the leftover material is passed into the colon where water is resorbed and, finally, the stool is excreted.

When the colon becomes irritated, we term this condition colitis – inflammation of the colon. Colitis can be either primary, due to a problem with the colon itself or, secondary, due to a problem somewhere else in the body causing the colon to become irritated.

Secondary colitis can be a common finding when there is a digestive problem in the small intestine. If the small intestine for any number of reasons is not completely digesting food, it can send inadequately digested product into the colon. The colon is not equipped to handle this stuff and the normal bacteria within the colon will begin to ferment this partially undigested material. The fermentation process can be very irritating to the colon to the point of causing the colon wall to bleed. If the irritation is severe enough, the colon can be impaired from its normal duty of resorbing water causing a change in the stool consistency. This can show up as loose stool or stool with a gelatinous mucous material surrounding it.

Diet change, although not apparently relevant in this case, can cause colitis. If a companion is suddenly fed a new diet without a weaning process, their digestive tract, specifically the small intestine, may not handle the new product well, leading to secondary colitis manifesting as blood in the stool and often diarrhea.

Primary colitis can be caused by any primary insult to the colon. A mass or multiple masses within the colon can cause colitis. So too can some types of intestinal parasites.

A visit to Andy’s veterinarian should provide an avenue to a diagnosis as to the cause for the intermittent blood his stool. Radiographs can be a very helpful tool in trying to distinguish between primary colitis and secondary colitis due to small intestinal inflammation. If the colitis is being caused by small intestinal disease, a biopsy of the small intestine may be necessary to determine the underlying cause and armed with a definitive diagnosis, appropriate treatment can be initiated to hopefully eliminate his problem.

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