Megacolon in Cats

What is megacolon?

The gastrointestinal tract terminates in the large intestine with a tubular organ called the colon. The colon serves as a site for the absorption of water and storage of fecal material; it ends at the rectum. The walls of the colon contain muscles that are stimulated to contract by nerves from the spinal cord. When the colon contracts, fecal material is pushed out of the body.

If the nerves to the colon do not function normally, the muscles of the colonic wall will not contract properly. If this happens, the muscles become stretched and the colon enlarges in diameter. This enlarged colon may have a diameter three to four times that of a normal cat. Rather than being pushed into the rectum in a normal manner, fecal material accumulates in the distended colon, resulting in severe constipation called obstipation. This massive enlargement of the colon and the resulting constipation is called megacolon.

What causes megacolon?

An injury to the spinal cord can cause megacolon. In addition, mechanical obstruction caused by tumors, foreign bodies, hairballs, and strictures can lead to megacolon.

" In most cases, we cannot determine the reason that the nerves to the colon stop functioning."

However, in most cases, we cannot determine the reason that the nerves to the colon stop functioning. This disease generally occurs in middle-aged to older cats, but has also been seen in cats as young as three to four years old. In cases that do not have an identifiable cause, the condition is termed idiopathic megacolon.

How is megacolon treated?

Usually, a medical approach is tried first, with surgery reserved for unresponsive or advanced cases. A medical approach involves the use of laxatives, stool softeners, colon wall stimulants, and high fiber diets. These do not correct the underlying cause, but they do allow fecal material to pass so the cat does not become constipated and ill.

"Medical approach may be successful for several months or years..."

The medical approach may be successful for several months or years, but will generally fail at some time. When this happens, surgery must be considered. A procedure called subtotal colectomy removes the non-functioning part of the colon. Although this procedure may involve removal of most of the colon, the anal sphincter will be left intact, so the cat should not lose bowel control. Most cats do reasonably well after this procedure with few permanent side effects.

Can the cat function without its colon?

Since one of the colon's primary responsibilities is to remove excess fluid from the fecal material, the cat that has had a subtotal colectomy will have rather soft stools immediately after surgery. In addition, it may pass several bowel movements each day. However, after one to two months, the stools will become formed and the cat will have an average of three bowel movements every two days. There should be no loss of fecal control.