Diarrhoea in cats ranges from a single loose stool after a change of food to a sign of serious disease. What separates them is how long it lasts, what it looks like, and how the cat is in itself.

Why it happens

The most common causes are a sudden change of food, eating something they should not have, intestinal worms, and stress. Beyond those: bacterial and viral infections, giardia and other protozoa, inflammatory bowel disease, pancreatitis, food intolerance, hyperthyroidism and kidney disease.

In kittens, worms and infectious causes dominate. In older cats, systemic disease becomes more likely.

Small intestine or large intestine

This sounds technical but it is something you can observe, and it helps us.

Large volume, watery, a few times a day, with weight loss suggests the small intestine.

Small amounts, many times a day, with straining, mucus or fresh red blood suggests the large intestine.

Note which pattern you are seeing before you come in.

What you can do at home

If your cat is bright, eating, drinking and there is no blood, you can watch it for a day.

Keep fresh water available at all times
Feed small amounts of a bland, easily digested food
Do not fast a cat for more than a few hours, and never for a full day
Keep the litter tray clean so you can see what is being passed
Do not change the food again in the middle of this

Do not give human anti-diarrhoeal medication. Several are toxic to cats. Do not give milk; most adult cats cannot digest lactose and it makes diarrhoea worse.

When to stop managing it at home

Bring your cat in if the diarrhoea lasts more than two days, if there is fresh blood or the stool is black and tarry, if vomiting starts as well, if the cat stops eating or drinking, if it becomes lethargic, or if it is a kitten or an older cat.

Dehydration is the real danger. A useful check is the gums: they should be moist. Dry, tacky gums mean fluid is being lost faster than it is going in.

What we do

An examination, a faecal test for worms and protozoa, and depending on the findings a blood count and biochemistry. Treatment addresses the cause; fluids are given under the skin or intravenously where the losses warrant it.

Bring a fresh stool sample if you can. It saves a day.

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