Published by: Ingrid King. Last Updated on: June 25, 2023 by Crystal Uys

vet holding a senior cat

Megacolon is a condition caused when too much fecal waste accumulates in the bowel. Megacolon can be congenital, but more commonly, it is an acquired condition that can be caused by poor diet, a foreign body in the colon, lack of exercise, or litter box and/or behavioral issues.

Constipation occurs when feces are retained in the colon. Feces become hard and firm, and the longer they stay in the colon, the more water is resorbed out of the colon. Eventually, if these fecal masses aren’t eliminated, the colon will become extended. This can lead to the colon muscles becoming so fatigued and stretched that they no longer function normally.


Signs include:

  • Constipation
  • Obstipation (chronic  constipation, which can eventually lead to obstruction)
  • Infrequent elimination
  • Straining to defecate, followed by small amounts of loose stool
  • Vomiting
  • Loss of appetite
  • Dehydration

Diagnosis of megacolon in cats

Your vet will take a complete health history of your cat, and perform a physical exam. Palpation of the rectum will reveal a hardened colon and a rectal exam will most likely find fecal impaction. In order to determine how severe the condition is and to identify or rule out underlying causes, your vet will also recommend other tests, including blood work, urinalysis, an ultrasound, X-rays with barium contrast studies, and possibly neurologic testing.

Vet examining cat in x ray room with e collar
Image Credit: PRESSLAB, Shutterstock

Treatment of megacolon in cats

The goal of treatment is to clean out the colon and identify issues that may have contributed to the condition. The type of treatment will depend on the severity of the condition, and may include use of laxatives and stool softeners. Severe cases may require repeated enemas to completely void the colon; some cats will require sedation for this procedure. Cats who are severely dehydrated may need to be hospitalized and given intravenous fluids. In severe recurrent cases, surgery to remove most of the damaged colon may be required.

Prevention of megacolon in cats

Megacolon can be prevented with healthy lifestyle management.

  • Feed a species-appropriate, raw or grain-free canned diet.
  • Give a good probiotic and digestive enzymes with each meal.
  • Keep your cat well hydrated by providing plenty of fresh water. A fountain can be a good option to get cats to drink more water.
  • Encourage your cat to exercise.
  • Provide enough litter boxes to encourage proper elimination. Some cats prefer separate boxes for urine and stool.

Most cats with megacolon will respond to treatment and lifestyle changes. For those who require surgery, the success rate is high and most cats will continue to lead normal lives.

Image Credit: Creative Cat Studio, Shutterstock

Featured Image Credit: Alice Rodnova, Shutterstock

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12 Comments on Megacolon in Cats: Signs, Diagnosis, Treatment & Prevention

  1. My cat has megacolon. He’s taking cisapride and I just switched him to Miralax because he really hates the lactulose prescribed for him. His brother is diabetic, and as they were strays when they came to the complex where I live there’s no way to know their early medical history, so in case there’s a genetic predisposition to diabetes in these guys I feel uncomfortable giving my cat lactulose. MacGregor’s stools are typically hard and very large, though the firmness has become more manageable with laxative. But he still may go for two days without a bowel movement. He’s eating the Royal Canin Gastrointestinal Fiber Support formula right now. Would you recommend the probiotic formula cited above for him, as well?

    • I would definitely add a good probiotic/digestive enzyme product. I like the Dr. Goodpet product I would also encourage you to discuss a better diet for him with a vet who is holistically oriented.

  2. Hi Ingrid,
    Our baby has had constipation issues off and on. It was much worse ruining medical treatment until we switched foods and changed vets. Now it happens when he is stressed or we are stressed and he’s feeling it. Our vet is recommending miralax 1/8 tsp dailyif it continues but I wanted your opinion. We have been using a probiotic from vetriscience. Any help is appreciated.

    • A probiotic is definitely indicated. You may also want to try canned pumpkin before you try the Miralax, it works really well for some cats.

  3. Our Zoey has “poop” problems. Have you ever heard of a cat that goes only about once a week? That’s Zoey. Despite the fact that she eats wet food only (with water and laxative added to it) and cisipride twice a day.

    What probiotic/digestive enzyme would you recommend? Maybe we should add that to her diet.

    • Once a week, even on canned food and with laxatives added, seems a bit worrisome. I like the Dr. Goodpet Feline Digestive Enzymes, they also contain probiotics:

      • I agree, Ingrid, it has me worried, too. But I’ve talked with my vet about it and she thinks as long as Zoey isn’t straining, isn’t vomiting, is eating, is acting otherwise normal, and when she does go, her *poops* aren’t hard, this may just be her way. I would have Zoey evaluated by a specialist, but she is a terror at vet’s and cannot be handled without being sedated. So I have chosen not to put Zoey through the stress.

        I may try the digestive enzymes and probiotics. If you have any other thoughts, let me know. Thanks.

        • Sounds like the right approach to me. If she’s otherwise happy and healthy, I don’t see the point of putting her through the stress of an evaluation, either. If you decide to try the enzymes/probiotics, let me know how she does.

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