Megacolon can have multiple causes, including narrowing of the pelvic area (due to a pelvic fracture), nerve injury, or spinal cord deformities. Rarer causes include cancer and inflammation. In nearly two-thirds of all cases, the condition is termed "Idiopathic Megacolon" because the cause cannot be found. However, it is thought to be due to an abnormality in the smooth muscle of the large intestine.
Symptoms depend upon severity of the condition, but in almost all cases, the stool is reduced or absent and is hard and dry. The cat may strain to defecate, spend long periods of time simply standing in the litter box, or return frequently to the litter box to try to defecate. The cat may defecate outside of the litter box. Severe straining may result in passing of mucous or blood. Occasionally a cat will develop diarrhea because the feces are irritating the intestine. The cat may vomit, even while he is straining to pass stool. As the condition becomes more severe, the appetite can decrease and weight loss is often noted. Ultimately, the cat may become lethargic and dehydrated.
Treatment of constipation and Megacolon
A cat with idiopathic Megacolon will first be appropriately hydrated with IV fluids. Then, a veterinarian will sedate the cat and perform an enema and deobstipation (manual removal of feces). These procedures are often followed with a low-residue diet and medications such as Lactulose and Cisapride. Some cats diagnosed with Megacolon do not recover adequately and may require surgery to remove much of the colon (a sub-total colectomy). In general, the prognosis is favorable, although some cats may experience diarrhea for weeks to months after the surgery.
If you suspect your cat has Megacolon, contact your veterinarian for proper diagnosis and treatment.