Why Do Cats Get Colitis? Causes, Risk Factors & Diagnosis

Colitis in cats, or inflammation of the large intestine (colon), can develop for many reasons, including dietary factors, stress, parasites, infections, and chronic disease. Understanding the possible causes of colitis and how a veterinarian diagnoses the condition helps lay the foundation for an effective treatment and management plan.

Causes & Risk Factors of Colitis in Cats

Colitis can develop for many different reasons. In some cats, the cause is temporary and easily treated, while in others it may be part of a chronic or more complex medical condition. Identifying the underlying cause is important so your veterinarian can create the best treatment and nutrition plan for your cat.

Dietary Factors

Diet plays a major role in digestive health, and dietary issues are a common cause of colitis in cats.

Potential dietary causes include:

• Dietary indiscretion, such as eating table scraps, garbage, plants, foreign objects, or other inappropriate items  
• Sudden or abrupt diet changes  
• Food allergies or food intolerances  
• Sensitivities to certain proteins, ingredients, or additives  
• Food-responsive enteropathy (FRE), where digestive signs improve with dietary management

Some cats develop colitis after eating something unusual or after a sudden food change. Certain ingredients may also irritate the large intestine in sensitive cats.

Infections & Parasites¹

Infections and intestinal parasites are common colitis in cats causes, especially in kittens, outdoor cats, shelter cats, and in multi-cat households.

Potential infectious causes include:

• Intestinal parasites such as roundworms, hookworms, Giardia, coccidia, and Tritrichomonas foetus  
• Bacterial infections, including Salmonella, Campylobacter, Clostridium, or bacterial overgrowth  
• Viral infections such as feline immunodeficiency virus (FIV), feline leukemia virus (FeLV), or feline infectious peritonitis (FIP)  
• Fungal infections, which are less common

So is colitis in cats contagious? The condition itself is not, but some parasites or infections may spread between animals or be associated with contaminated food, water, or environments.

Stress & Behavioral Factors

Cats are very sensitive to stress and environmental change. Stress and anxiety in cats can affect the digestive tract and the healthy bacteria living within it, sometimes leading to stress colitis in cats.

Common stressors include:

• Moving to a new home  
• Boarding or travel  
• Changes in routine  
• Introduction of new pets or people  
• Conflict with other household pets  
• Litter box changes  
• Loud noises or household disruptions  
• Sudden diet changes

Cats with anxious or nervous personalities may be more prone to stress-related digestive upset.

Bacterial Imbalance & the Gut Microbiome²

A healthy balance of bacteria in the intestinal tract, called the gut microbiome, plays an important role in digestive health. Disruptions in this balance may contribute to inflammation within the colon.

Changes in the microbiome may occur because of:

• Stress  
• Illness  
• Antibiotic use  
• Dietary changes

Disturbances early in life can affect long-term intestinal health in cats.

Inflammatory Bowel Disease (IBD)/Irritable Bowel Syndrome (IBS)

You may be wondering, can cats have IBS or IBD, similar to what people have? The answer is yes.

Chronic inflammation in the digestive tract may be associated with IBD. Cats with IBD can develop recurring vomiting, diarrhea, weight loss, or appetite changes. In some cases, inflammation primarily affects the colon, resulting in chronic colitis signs.

IBS is sometimes used to describe stress-sensitive digestive conditions, although true IBS is less clearly defined in cats than in people.

Other Medical Conditions

Several underlying medical conditions may contribute to colitis or cause similar digestive signs:

• Pancreatitis. Inflammation of the pancreas can cause vomiting, diarrhea, abdominal pain, and decreased appetite.
• Kidney disease. Chronic kidney disease and other kidney problems may contribute to dehydration, nausea, appetite changes, and gastrointestinal issues.
• Liver disease. Liver disorders can affect digestion and may lead to vomiting, diarrhea, weight loss, or poor appetite.  
• Hyperthyroidism. An overactive thyroid gland can cause weight loss, increased appetite, vomiting, and diarrhea in older cats.
• Gastrointestinal cancer. Cancers such as lymphoma, adenocarcinoma, or polyps can cause chronic digestive signs, weight loss, or blood in the stool.
• Intussusception. In this condition, one part of the intestine telescopes into itself, causing blockage and digestive distress.  
• Reactions to antibiotics or medications. Some medications can disrupt normal gut bacteria or irritate the digestive tract, leading to diarrhea or colitis signs.
• Systemic illness or infections. Underlying diseases affecting the body as a whole may also contribute to inflammation within the digestive tract.

Because many of these conditions can cause overlapping symptoms, testing is often needed to determine the underlying cause.

Age-Related Considerations

A cat’s age can sometimes provide clues about the underlying cause of colitis:

• Younger cats and kittens are more likely to develop colitis related to parasites, infections, or dietary indiscretion.  
• Adult cats may develop stress-related colitis, food sensitivities, or inflammatory conditions.  
• Older cats are more likely to have chronic diseases such as IBD, hyperthyroidism, or gastrointestinal cancer.

Idiopathic Colitis²

In some cats, no specific underlying cause can be identified despite testing. This is called idiopathic colitis. Even when a clear cause is not found, many cats can still be managed successfully with nutrition, stress reduction, medications, and supportive care.

Diagnosis of Colitis in Cats²

Because many digestive conditions can cause signs similar to colitis, your veterinarian may recommend several tests to better understand what is affecting your cat’s digestive health.

Diagnosis often starts with a detailed history and physical examination. Your veterinarian may ask about:

• Stool appearance and frequency  
• Blood or mucus in the stool  
• Vomiting, appetite changes, or weight loss  
• Diet and recent food changes  
• Stress or environmental changes  
• Exposure to other pets  
• Travel history  
• Current medications  
• Parasite protection history

A physical exam helps assess hydration, body condition, abdominal discomfort, and overall health.

Fecal Analysis

Fecal testing helps look for parasites, abnormal bacteria, or infectious organisms that may contribute to colitis in your cat. Tests may include fecal cytology or flotation, Giardia testing, and PCR testing.

Blood Work

Blood tests help evaluate overall health and screen for conditions such as:

• Dehydration  
• Hyperthyroidism  
• Infection or inflammation  
• Kidney disease  
• Liver disease

Imaging and Other Tests

• Abdominal x-rays or ultrasound may help identify intestinal thickening, foreign material, masses, or other abdominal abnormalities.
• Urinalysis helps assess hydration, kidney function, and urinary tract health.

In some cases, additional tests such as colonoscopy or biopsies may be needed, especially if cat colon inflammation symptoms keep coming back. These include:

• Endoscopy/Colonoscopy. A small camera is used to examine the digestive tract for inflammation, ulcers, or masses under anesthesia.
• Biopsies. Small tissue samples may be collected to help diagnose conditions such as IBD or gastrointestinal cancer. This may be done as part of an endoscopy or performed surgically.

Conclusion: Recap of Colitis in Cats Causes

The causes of colitis in cats can vary widely, which is why a thorough evaluation is an important step in the process. Identifying the underlying cause allows your veterinarian to develop a targeted treatment and management plan tailored to your cat’s specific needs.

With a diagnosis in hand, the next step is focusing on treatment, nutritional support, and long-term digestive health.

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For more expert tips on cat health, explore our other cat symptom articles.

Nutrition Science sourced from the Purina Institute.  

References

1. Schmid SM. Infectious colitis in dogs and cats: diagnosis, management, and clinical outcomes. Vet Clin North Am Small Anim Pract. 2026;56(3):769-787. doi:10.1016/j.cvsm.2026.01.004

2. Schmid SM. Large-intestinal disorders in dogs and cats: diagnosis, management, and clinical outcomes. Vet Clin North Am Small Anim Pract. 2026;56(3):747-768. doi:10.1016/j.cvsm.2026.01.005