Megacolon is nothing to laugh about, even though I can’t help but picture a segment of large intestine decked out as a superhero right now (have I been spending too much of my free time with five-year-olds this summer?). The disease is all too common in cats, and despite having a fair prognosis, can be extremely frustrating to deal with.

Megacolon is characterized by a distended large intestine (colon, in other words) that is filled with abnormal amounts of feces. This may occur as a primary disease, typically caused by colonic muscles that don’t contract normally, or as a result of prolonged or severe constipation essentially stretching out and damaging the large intestine. Whatever the root of the problem, affected cats have some combination of the following symptoms:

  • Straining to defecate
  • Pain while defecating
  • Producing small amounts of hard fecal matter that may contain blood
  • Loss of appetite
  • Abdominal discomfort

Some cats produce small amounts of liquid feces after straining, which can lead owners to think that they are suffering from diarrhea rather than constipation.

Diagnosing megacolon is not too difficult. A veterinarian will usually feel a feces-filled large intestine during the physical exam and abdominal X-rays can confirm that the colon is much bigger than it should be. Additional diagnostic tests (e.g., blood work, a urinalysis, and abdominal ultrasound) may be necessary to determine if megacolon has developed in response to another problem.

Treatment for megacolon involves getting the impacted feces out and preventing future build-ups. The best case scenario involves giving the constipated cat an enema and standing back while he or she takes care of business from there. Unfortunately, things don’t always play out that way. Some of my more vivid memories from veterinary practice involve manually removing huge numbers of hard-as-rocks fecal balls from constipated cats. This procedure necessitates anesthesia (for the cat, not for me, unfortunately) and lots of water, lubrication, patience, and faith in latex gloves.

To help prevent future episodes of constipation, I prescribe some combination of fluid therapy, stool softeners (lactulose), medications that enhance muscular contractions within the wall of the colon (cisapride), and a change in diet. Most cats respond best to a highly digestible food that reduces the amount of feces they produce. If that doesn’t work, we’ll try a high-fiber diet, which can make the cat’s stool softer and easier to pass.

Many cats respond to this type of treatment well, although some may need the occasional enema to keep things moving freely (Never use an enema on your cat without first consulting a veterinarian. Some of them are toxic.)

When medical management fails, surgically removing the non-functioning portion of a cat’s colon is the best remaining option. It sounds extreme, but most cats respond to the surgery very well. Many form looser than normal stools post-operatively, but the situation generally improves with time and dietary manipulation. The surgery can return life to near normal for a cat and its owner alike and probably needs to be recommended more frequently than it currently is. 

Dr. Jennifer Coates

Image: Chan Wing Tat / via Shutterstock