Colitis in cats: causes, symptoms and treatment

Summary

Colitis in cats occurs when the colon, also known as the large intestine or large bowel, becomes inflamed, causing frequent small volume diarrhoea, mucus and straining. Triggers include stress, diet intolerance, parasites and infection. A vet exam and faecal tests guide therapy. Dietary management, probiotics and targeted medications usually control signs. Reduce stressors and make gradual diet changes to limit flare ups.

What is colitis in cats?

The colon, also known as the large intestine or large bowel, is the lower part of the digestive tract which is responsible for the final stages of the digestive process. The colon stores and removes water from the faeces (poo) prior to their elimination from the body. When the lining of the colon becomes irritated and inflamed, the colon’s ability to absorb water from the faeces is disrupted, resulting in loose, watery and sometimes bloody faeces.

Feline colitis is a chronic bowel disease resulting from inflammation of the colon which presents as diarrhoea with some distinguishing characteristics, including increased frequency of bowel movements, straining as well as blood or mucus on the faeces.

Colitis in cats can be acute, coming on suddenly and lasting only a few days, chronic, lasting for at least two to three weeks, or episodic, coming and going over time. Occasional bouts of acute colitis are fairly common in some cats and usually resolve on their own. However, it is important to look out for frequent recurrence or worsening of the condition. Chronic feline colitis is more common in middle-aged and older cats and may be associated with an underlying medical condition.

Symptoms of colitis in cats

The symptoms of colitis can range from sporadic and mild to enduring and severe. As the owner of a cat with colitis, you may observe a combination of the following symptoms:

Faeces-related symptoms, commonly observed in cats with acute, chronic and episodic colitis:

• Frequent diarrhoea or abnormal faeces – stools may start off solid but finish off watery and loose
• Straining to defecate, may appear constipated
• Difficult or painful evacuation (dyschezia)
• Frequent bowel movements where little is passed
• Bright, fresh red blood in the faeces (hematochezia)
• Mucus in the faeces
• Increased urgency to get to the litter box, defecating outside the litter box

Additional symptoms more common to chronic and episodic colitis:

• Reduced appetite
• Progressive weight loss
• Lethargy
• Sleeping more than normal
• Vomiting – in around 30% of cases
• Dehydration
• Loss of appetite
• Poor coat and body condition
• Shying away from being touched
• Hiding from people or other pets

Expert advice from Dr Felicia:

Colitis is usually characterised by frequent trips to the litter tray with only small amounts of diarrhoea, often with mucus or blood. Cats with acute colitis are generally otherwise well apart from discomfort associated with using the tray, though some may be a little more reserved and interacting less with the family.

When to see a vet

Contact your vet if your cat has diarrhoea that lasts more than a day or two, keeps coming back, contains blood or mucus, or is accompanied by vomiting, lethargy, weight loss, reduced appetite or signs of dehydration.

You should seek urgent veterinary advice if your cat is repeatedly straining in the litter tray and you are not sure whether they are passing urine or faeces. Straining can be mistaken for constipation or colitis, but a cat that is trying to urinate and passing little or no urine may have a urinary blockage, which is a medical emergency.

Causes of colitis in cats

Inflammation of the colon can be triggered by a wide-range of factors, from ingesting human food products to parasites and fungi in the cat’s gastrointestinal tract. There are also certain diseases, such as hyperthyroidism and diabetes, that can cause or contribute to colitis in cats. It is essential to identify the specific cause in each case of feline colitis, so that appropriate diagnosis and treatment can follow.

Some of the more common causes of colitis in cats are:

• Stress and anxiety – a break in routine, a new pet in the family, moving houses
• A reaction to antibiotics or other medicines
• Dietary intolerance, usually in response to a substance in the diet such as a preservative or food colouring
• Dietary allergy, usually resulting from a reaction with a protein antigen such as beef, wheat and corn
• Consumption of unsuitable foods, for example, spoiled food, a plant or garbage
• Consumption of a foreign body
• Bacterial infections, for example salmonella, campylobacter, E.coli
• Intestinal parasites, for example roundworms, giardia, coccidia, tritrichomonas foetus, protozoal infection
• Viral infections, including Feline leukemia virus (FeLV), Feline immunodeficiency virus (FIV), Feline infectious peritonitis (FIP)
• Specific inflammatory disorders of the colon (different cell types found in the colon may be predominantly inflamed)
• Inflammatory bowel disease (IBD)
• Acute infectious enterocolitis
• A primary disease or disorder that causes or contributes to colitis or colitis-like symptoms in cats, such as colonic and bowel cancers, kidney disease, hyperthyroidism, pancreatitis or intussusception (telescoping of the bowel into itself)

Expert advice from Dr Felicia:

Causes of colitis vary hugely and considerations for addition investigation include whether the appetite is affected, whether any weight loss has occurred and if there are any other significant abnormalities on the physical examination, such as thickened intestines or small, shrunken kidneys.

How is colitis in cats diagnosed?

If a bout of diarrhoea lasts for longer than a few days, or if diarrhoea becomes a recurring issue, it is essential to take your cat to the vet to investigate why. Colitis is a complicated condition that requires an accurate diagnosis before effective treatment can commence. Other illnesses may cause similar clinical symptoms, and these should be considered when a cat is evaluated for colitis.

As there are many potential causes of colitis in cats, you will need to inform your vet of your cat’s complete history, including:

• Symptoms you have noticed
• Recent exposure to other cats
• Diet, and any recent changes to it
• Anything out of the ordinary that your cat may have eaten, such as people-food, trash
• Anywhere out of the ordinary that your cat may gone

If colitis is suspected, your vet will perform a combination of tests to identify the underlying cause, including:

• Chemistry profile to evaluate for kidney, liver, and pancreatic disease
• A complete blood count (CBC) to look for infection, inflammation, anaemia, and other blood-related conditions
• Faecal tests to look for parasites, bacteria and giardia
• Urinalysis to assess kidney function
• X-ray and/or abdominal ultrasound to evaluate the gastrointestinal tract and thickness of the intestines, and to check for abnormalities such as tumours and fluid
• Electrolyte tests to check for dehydration and electrolyte imbalance
• Pancreas-specific tests to rule out or confirm pancreatitis
• Serum thyroid hormone concentration to investigate hyperthyroidism
• Tests to investigate FeLV and FIV status

Additional tests may be performed if routine tests are inconclusive or if the colitis is severe or does not resolve with treatment, such as:

• Colonoscopy with a flexible fibreoptic endoscope, to visualise the lining of colon check for polyps and tumours and take biopsies of the inner surface of the colon for microscopic examination to ascertain the type of inflammatory cell present,
• Proctoscopy (endoscopic examination of the rectum) to examine and take biopsy samples of the terminal end of the colon

Expert advice from Dr Felicia:

Testing for colitis may start off with looking at the faeces, looking at the gastrointestinal tract itself via ultrasound or looking at bloodwork to see if there are metabolic effects of the colitis evident. These can be done in a stepwise manner or all at once for patients with more concerning disease.

Treatment for colitis in cats

The therapeutic goals of treatment for feline colitis are to relieve pain and discomfort, and to restore normal bowel function. If there is an underlying medical condition which is causing colitis or colitis-type symptoms, this will need to be identified and treated.

The choice of treatment will depend on the causes of the inflammation and the frequency and severity of symptoms. Acute colitis often resolves itself in a few days without requiring treatment; however, chronic or episodic colitis almost always requires medical attention and imaging alongside treatment trials which can help to narrow down the cause. Where the cause is an infection or parasite, colitis can be cured, but generally, it can only be controlled through appropriate medical management and dietary modification to promote gut healing and recovery.

Dietary modification

Symptoms of colitis may resolve simply by changing the cat’s diet, often within a week of making the changes. There is no one ideal diet that will consistently resolve colitis in cats.

Your vet may recommend one or more of the following options:

• Bland diet, given in small portions, for example rice, fat-free, plain flavoured yogurt, pumpkin, plain cooked chicken
• Soluble fibre added to the diet (in the form of food or supplements, for example psyllium) – may relieve straining and discomfort; the amount of fibre may be gradually reduced
• Fatty acid supplements – soothe the irritated lining of the colon
• Elimination diet – cutting out certain foods – if food allergies or intolerances are suspected
• Novel protein diet – a single, new form of protein, such as venison, lamb or rabbit (vet-prescribed is preferable to over-the-counter, which may contain allergens not listed on the label)
• Hydrolysed diet – a single protein source, often soy, rice or potato, that has undergone a process that makes them highly digestible

Expert advice from Dr Felicia:

Cats can be fussy and difficult to convince to eat new diets. Usually heating up the food can help to encourage cats to try something different, or the addition of something tasty on top (eg. Home cooked chicken) may entice them.

Medication

Medication may be needed depending on the underlying cause. Your vet may prescribe or recommend:

• Medication that thickens the faeces (oral motility modulator), for symptomatic relief until the inflammation is under control
• Anti-parasitic and deworming medication, if intestinal parasites are identified
• Antibiotics, if dietary modification is unsuccessful, to determine if the colitis is ‘antibiotic-responsive’
• Probiotics, or live microorganisms, that, taken alone or in combination with antibiotics, can be beneficial in modifying the gut bacteria for as long as they are being taken
• Immunosuppressive drugs – corticosteroids –in severe cases and/or where dietary modification and antibiotic treatments have failed, which requires careful monitoring by the vet
• If there is a reduction in appetite anti-nausea medication may be given to help encourage your cat to eat

Expert advice from Dr Felicia:

Cats can be hard to medicate! Discuss with your vet which medications are highest priority and also the possibility of compounding medications into liquids or transdermal formulations so medicating your cat doesn’t become any source of stress for them.

Hospitalisation

Hospitalisation may be required if the colitis is severewhich in particularly young or old patients can cause dangerous dehydration, requiring treatment with intravenous fluid and electrolyte replacement.

Home care and management

For cats recovering from colitis, supportive care at home can help reduce flare-ups and make symptoms easier to monitor. Your vet may suggest:

• Ensure that fresh water is freely available and easily accessible
• Provide a calm, quiet, safe indoor environment, away from other animals if possible
• Only offer cooked food as bacterial and viral load on raw meat is much higher compared to cooked
• For cats with a reduced appetite heating up the food can make it more appealing for them
• Keep the litter tray clean as cats can often be fastidious about the state of their litter tray. Consider offering a second tray if the colitis is so frequent it is hard to keep up with maintaining its cleanliness.

Life expectancy for cats with colitis

The outlook for cats with colitis varies greatly, depending on the cause of the condition and the effectiveness of the treatment provided. If the cause is eliminated or effectively managed, the prognosis for long-term control is good. Most infectious causes of colitis are curable. However, if treatment does not resolve the cat’s colitis, colon cancer or another serious illness or disorder might be involved, which greatly alters the prognosis.

Because it is difficult to predict the costs of veterinary care, it can help to have measures in place to help prepare for the unexpected. Pet insurance can help by covering a portion of the eligible vet bill if the unexpected does happen.

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Can colitis in cats be prevented?

Not every case of colitis can be prevented, but you may be able to reduce your cat’s risk by:

• Feeding a consistent, complete and balanced diet
• Making any diet changes gradually
• Avoiding table scraps and unsuitable human foods
• Keeping parasite prevention up to date
• Reducing stress in multi-cat households
• Providing enough litter trays, resting areas and hiding places
• Keeping toxic plants, rubbish and spoiled food out of reach
• Booking regular veterinary check-ups, especially for older cats

Overview

Colitis in cats occurs when the colon is inflamed, usually resulting in pain and discomfort. Colitis can either be chronic, lasting for long periods of time, or acute, occurring for just a few days and resolving on its own without treatment. One of the main symptoms of colitis is diarrhoea, or loose and watery stools with mucus.

Chronic colitis can be a complex and frustrating condition to treat that may require frequent vet visits, with multiple diagnostics and treatment trials to arrive at anaccurate diagnosis and effective treatment  to manage. Your vet will perform a physical examination and do a combination of tests to identify the cause. Treatment in most cases entails dietary modification and /or medication. More complex cases may involve faecal testing, abdominal imaging as endoscopic biopsy.

Sources:

“Colitis in Small Animals”, MSD Veterinary Manual, https://www.msdvetmanual.com/digestive-system/diseases-of-the-large-intestine-in-small-animals/colitis-in-small-animals. Accessed 23 Jun 2026.

“Differentiation of Small Intestinal from Large Intestinal Diarrhea”, Merck Veterinary Manual, https://www.merckvetmanual.com/multimedia/table/differentiation-of-small-intestinal-from-large-intestinal-diarrhea. Accessed 23 Jun 2026.

“Inflammatory Bowel Disease”, Cornell University College of Veterinary Medicine, https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/inflammatory-bowel-disease. Accessed 23 Jun 2026.

“Diarrhea”, Cornell University College of Veterinary Medicine, https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/diarrhea. Accessed 23 Jun 2026.

“Feline Lower Urinary Tract Disease”, International Cat Care, https://icatcare.org/articles/feline-lower-urinary-tract-disease. Accessed 23 Jun 2026.

“Urethral Obstruction in Cats”, International Cat Care, https://icatcare.org/articles/urethral-obstruction-in-cats. Accessed 23 Jun 2026.