Megacolon in Cats

Megacolon manifests as chronic constipation. Alongside difficulty defecating and dry, hard fecal matter, associated symptoms include:

• Pain in the abdomen
• Lack of appetite
• Lethargy

Constipation in cats requires prompt veterinary care. Early diagnosis of chronic constipation and treatment to remove fecal burden prevents permanent damage to the colon. Once the colon is permanently dilated, the defect requires surgical treatment.

Constipation and megacolon are common in cats. Prompt veterinary attention is necessary for cats suffering from chronic constipation in order to prevent megacolon. Most cases are initially managed through medical treatment, including enemas or manual removal of feces. Depending on the underlying cause, repeated episodes of megacolon may occur. In recurring cases or severe cases, surgical intervention is required to remove areas of permanently damaged colon. Most cases have a good long-term prognosis with appropriate management.
Depending on the underlying condition, constipation may recur despite medical management. Each episode has the potential to cause permanent damage, and requires prompt veterinary care.

The three types of megacolon are hypertrophic, neurogenic, and idiopathic dilated.

Hypertrophic megacolon is the result of an obstruction in the colon that disrupts the passage and evacuation of stool. Feces collects in the colon, compacting into an overwhelming burden which dilates the colon. If left untreated, permanent colon damage results. Underlying causes of hypertrophic megacolon include:

• Injuries, such as pelvic fractures, that narrow the pelvic canal (pelvic canal stenosis)
• Poorly digested, hard matter (hair, bones, litter) in the feces
• As a secondary response to other medical intervention such as medication, radiation, or electrolyte imbalances that disrupt colonic contraction
• Compression of the colonic wall by scar tissue, tumors, or herniation

Hypertrophic megacolon is reversible if detected early.

Neurogenic megacolon results from neurological disorders that disrupt the innervation of the large bowel. Disruption of the innervation results in the failure of the colon or rectum to relax when stimulated by the passage of feces, causing an accumulation of fecal material and dilation of the colon.

In cases where hypertrophic and neurogenic megacolon are excluded, the diagnosis is idiopathic dilated megacolon, meaning the chronic condition does not have a known cause. Any case of untreated, repeated constipation leads to obstipation, the permanent loss of function of the colon.

Diagnostic tools to investigate chronic constipation include

• Physical exam
• Blood work
• Diagnostic imaging, including ultrasound and X-rays
• Contrast studies of gastrointestinal tract
• Colonoscopy

Initial treatment focuses on medical management of constipation. Strategies include:

• Hydration, including IV fluids where necessary
• Enema
• Deobstipation: a surgical method to manually remove feces from the bowel

Note: there is no safe way to perform an enema on a cat at home. Phosphorous fleet enemas are toxic to cats and should never be performed.

Once the fecal burden is removed, medical management to avoid further constipation includes moving to a low residue diet, prescription laxatives, and medication to promote gastrointestinal motility. If constipation is resolved before permanent damage occurs, follow-up management with laxatives and medications may be recommended to prevent future episodes. In cases where the cat does not respond to medical management, or stops responding, surgical treatment is necessary. Subtotal colectomy is the surgical removal of the part of the colon that is no longer functioning and is often curative in these cases. After surgery, diarrhea, increased frequency of defecation, difficult defecation, and occasional dropped stool may occur for a few weeks to months. Post-operative constipation occurs in some cases. Rarely, some dysfunctional bowel is left intact and requires a second surgery. Long-term medical support may be required. Some cats experience recurrent obstipation that is progressively more difficult to solve.

Avoiding the underlying causes of constipation helps prevent some causes of megacolon. Considerations include:

• A high fiber diet
• Adequate hydration
• Proper electrolyte balance
• Brushing cats regularly to prevent ingestion of loose hairs during grooming
• Preventing dietary indiscretion

Megacolon is common in cats.

Treatments include:

• Enemas
• Laxatives
• Surgical removal of feces.
• Removal of tumors, strictures, or hernias
• Subtotal colectomy