Feline Megacolon
Stephen Sheldon, D.V.M.

Although the name of this feline disease sounds funny, anyone whose cat had had it can tell you it is no laughing matter. Megacolon is the name of a disease that causes the colon or large intestine to enlarge to astronomic proportions. These poor kitties undergo a lot of pain and discomfort trying to defecate and many are euthanized due to the difficulty treating the condition.

The most common form of megacolon in cats is the Idiopathic form. This means we don’t know what causes it. What we do know is that it is a disease of the smooth muscles of the colon (ok, who knows the 3 types of muscles present in mammals? Answer later). Any age cat can be affected and males often outnumber females in many studies. Other forms of megacolon are called acquired or congenital. Congenital megacolon is caused by a birth defect; Manx cats are suspected of having this form. It is similar to Hirschsprung’s disease in humans in which the nerves to the rectum don’t form properly and feces becomes retained causing an obstruction.

Acquired megacolon has many causes, the only real common one being behavioral. Some cats have psychological problems defecating in the litter box. A new type of cat litter may be the cause or it could be competition with another cat or the cat may just be a very nervous type. Feces becomes retained and the colon stretches, and, just like a pair of panty hoses the colon loses its’ elasticity. Another cause of megacolon is trauma to the pelvic region. Fractures, tumors, prior surgeries with excess scar tissue, and rectal strictures are all examples of trauma. There are also some metabolic conditions reported to cause megacolon: high blood calcium, low blood potassium, and low thyroid hormone levels have all been implicated.

So how do you know if your cat has megacolon. Well, first off they will be spending a lot of time in the litterbox trying to defecate. Most of these cats are very constipated and some may even be obstructed. Believe it or not some may have diarrhea as liquid portions of stool may be the only thing that can escape around the blockage. I have seen more than one kitty with megacolon where the presenting complaint was for diarrhea. Some owners may notice unusually hard stools or notice that their cats have not had a bowel movement in a few days (some cats, like some people, do not regularly defecate daily. Personally my theory is if they could learn to read the sports page they would defecate more regularly). Other common signs are crying when defecating, weight loss, anorexia, and depression.

The diagnosis of megacolon is pretty straightforward. The history of the patient with a physical examination and radiographs are all that is usually needed to diagnose it. A good abdominal palpation can often reveal a huge colon with fecal retention, and/or obstruction. Radiographs are used to confirm this. Further tests will be done to try and nail down a cause; if one is not found we call it idiopathic megacolon.

Treatment is tedious and can be difficult. First the patient must be rehydrated using intravenous fluids. Then they are anesthetized and the feces must be manually extracted from the colon via the rectum. This is painful and traumatic for the kitties and it can be difficult for the doctors. Often we can only get a portion of the feces out in one session and may need to repeat it daily for a few days to get the colon cleaned out. If we are successful we place the patients on a high fiber diet and medications such as lactulose to soften the stools and propulsid to help the muscles of the colon contract more forcefully.

Pumpkin pie filler is also a good way to add bulk and fiber to the diet. Many of these cats will suffer relapses even with appropriate diet and medications. Laxatone and other petroleum based hairball products are ineffective for megacolon

If we cannot remove the obstruction or if the owners have difficulty medicating the cat or if we just get too many relapses we can correct the problem surgically. The procedure is called a subtotal colectomy and about 90% of the colon is removed. It has a high rate of success (once we get by the immediate post op complications which can occur because this is often a "dirty" surgical field). Unfortunately, cats with a subtotal colectomy also occasionally suffer relapses of constipation even though they don’t have a colon. As I mentioned earlier, many cats with this condition are euthanized by frustrated owners and veterinarians alike.

So now you know another feline disease with a funny name. If this disease is detected in its’ earlier states it is much easier to manage than if it is allowed to progress. This isn’t always easy to do as there are no tests that will show us which cats are at risk. If your cat is having difficulty defecating go to your veterinarian sooner than later; the more the colon stretches out the harder it will be to treat.

Trivia Answer: By the way, the 3 types of muscles in mammals are: smooth, skeletal, and cardiac.