Moderate severity

Colitis (Inflammation of the Colon)

Inflammation of the large intestine that causes typical "large-bowel diarrhoea" — frequent, urgent, small stools often streaked with fresh red blood or slimy mucus.

⚠️ Common symptoms

Frequent, urgent trips to the litter tray, often producing only a little each timeSoft or watery stools with a jelly-like coating of mucusStreaks or fresh drops of bright red blood on the stoolStraining and discomfort while passing a motionAccidents outside the tray because of the sudden urgencyUsually still bright and eating in mild cases, though it may recur

Colitis simply means inflammation of the colon, the large intestine, and it produces a very recognisable pattern that vets call large-bowel diarrhoea. Rather than large puddles of watery stool, an affected cat makes frequent, urgent, small deposits — often dashing to the tray again and again, straining, and producing just a little each time. That little is typically soft and coated in a jelly-like mucus, and it is frequently streaked with fresh, bright red blood. The blood looks alarming but, because it comes from the very end of the gut, it is usually a sign of surface irritation rather than a catastrophe.

One reassuring feature of many colitis cases is that the cat often seems otherwise well — bright, eating, and behaving normally between urgent trips to the tray. That said, the urgency can lead to accidents outside the box, which owners sometimes mistake for a behaviour problem when it is really a physical one.

The list of possible causes is long. Parasites and infections are among the most common, which is why vets often treat for worms and protozoa as part of the work-up. Dietary factors loom large too: an abrupt food change, scavenged rubbish, or a food the cat cannot tolerate can all inflame the colon. Stress is a genuine trigger in some cats, and in cases that keep coming back the real culprit is often inflammatory bowel disease or a food allergy simmering underneath.

Most acute bouts respond well to simple measures — a bland or novel diet, added fibre, parasite treatment and a little time — and settle within days. The reason to involve a vet rather than wait it out is twofold: to relieve the cat and to find out what is driving it, particularly when blood, mucus and recurrence point towards a treatable underlying condition. Chronic or repeated colitis is a signal to dig deeper rather than simply riding out each flare.

🔍 Causes

Colitis has many possible triggers. Intestinal parasites and infections are common culprits, as are dietary upsets — a sudden food change, dietary indiscretion, or a food intolerance. Stress can provoke or worsen it, and in longer-standing or recurrent cases the underlying problem may be inflammatory bowel disease, a food allergy, or, less often, growths in the colon. Sometimes an acute bout has no single identifiable cause and settles with simple supportive care.

🛡 Prevention

Introduce any new food gradually over a week or more rather than switching overnight, keep cats up to date with routine worming, and prevent scavenging of bins or spoiled food. Keeping stress low — with predictable routines, enough litter trays, and calm introductions to new pets or people — helps cats prone to stress-related flare-ups. For a cat with a known food trigger, sticking rigidly to the diet that suits them is the best prevention.

💊 Treatment

Treatment depends on the cause but often starts with a short spell of a highly digestible or novel-protein diet and added fibre to bulk and settle the stool. A vet may prescribe treatment for parasites even before results come back, since these are a common trigger, and may add anti-inflammatory medication or specific therapy where an underlying disease such as inflammatory bowel disease is found. Probiotics can help restore a healthy balance of gut bacteria. Ensuring the cat stays hydrated matters, and identifying and removing any dietary or stress trigger is key to stopping it coming back.

When to see a vet: See a vet if diarrhoea contains blood or mucus, if it keeps returning, or if it lasts more than a day or two, and sooner if your cat is also lethargic, off its food, vomiting, or straining without producing anything. While a single mild bout may pass, blood in the stool and recurring diarrhoea always warrant investigation, both to treat the cause and to rule out parasites, infection or the inflammatory bowel disease that often lies behind chronic colitis.

⚕️ Medical disclaimer

  • This information is educational only and is not a substitute for veterinary advice.
  • Symptoms overlap between conditions — only a vet can diagnose accurately.
  • Never withhold treatment or self-medicate based on information found online.
  • When in doubt, call your vet. Early intervention almost always leads to better outcomes.

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