Overview of Megacolon in Cats
Megacolon is a condition of extreme dilation and poor motility of the colon, usually combined with accumulation of fecal material and the inability to evacuate it. The majority of cases (62 percent) are “primary” or “idiopathic,” which means there is no obvious reason for the condition. Some cases are “secondary,” meaning that something has interfered with normal defecation for a prolonged period of time, causing chronic constipation, with megacolon occurring as a sequela. Recent studies have shown that cats with idiopathic megacolon have a defect in the ability of the muscle in the colon to contract.
Megacolon can occur in any age, breed, or sex of cat, however, most cases are seen in middle aged cats (average age is 5.8 years). Most cases are in males (70 percent males, 30 percent females). Megacolon can be a frustrating and difficult condition.
What to Watch For
Decreased or absent defecation
Multiple, unproductive efforts to defecate
Dry, hard feces
Other systemic signs of illness as a result of prolonged inability to defecate, such as anorexia, lethargy, weight loss and vomiting
Diagnosis of Megacolon in Cats
Megacolon is typically diagnosed based on history and physical exam finding. Determining the severity and any underlying causes requires diagnostic tests. Tests may include:
Complete blood count
Careful digital rectal exam
Treatment of Megacolon in Cats
Treatment for megacolon is aimed at removing the fecal matter and trying to correct any underlying causes of megacolon. Treatment may include:
Dietary modification (high fiber diets)
Drugs that make the colon contract
Manual extraction of feces
Home Care and Prevention
Home care for megacolon is to maintain a proper diet and exercise. This can help the cat to eliminate feces. Also important is the administration of all prescribed medication.
If you find your cat straining excessively, vomiting or not eating, or if there is or no stool production, prompt examination and treatment by your veterinarian is recommended.
Prevention of megacolon can be difficult. Proper diet, exercise and regular grooming can help reduce the risk of constipation. Preventing constipation in cats with megacolon may require the occasional use of laxatives.
In-depth Information on Feline Megacolon
Constipation is a clinical sign characterized by absent, infrequent, or difficult defecation associated with retention of feces within the colon and rectum. In cats, the colon has evolved to serve two functions: extraction of water and electrolytes from the colon contents and to control defecation. Anything that prevents normal defecation for a prolonged period of time can lead to megacolon, which is a condition of extreme dilation of the colon with inability to expel feces.
There are a variety of conditions that lead to megacolon.
Excessive narrowing of the pelvic canal, which blocks the passage of the feces, most commonly due to abnormal healing of pelvic fracture (23 percent)
Neurologic injury (6 percent)
Manx cats born with a spinal cord deformity (5 percent)
Idiopathic, which means there is no known reason why the condition developed (62 percent)
Recent research has shown that cats with idiopathic megacolon have a defect in the muscle present in the walls of the colon.
Although most cats with the disorder are brought to the veterinarian because of reduced, absent, or painful defecation ranging from days to weeks, some cats will be seen to have blood in their feces, or diarrhea. This is because the dry hard feces can irritate the lining of the colon and cause it to produce blood and excessive mucus, which can be mistaken for diarrhea. The prolonged inability to defecate can also lead to some non-specific systemic signs such as weight loss, poor or absent appetite, lethargy, and vomiting.
Diagnosing the underlying potential cause of megacolon can be difficult. Various diagnostic tests are recommended to evaluate the overall health of your cat as well as try to find an underlying cause.
Complete blood count, chemistry panel, urinalysis. Although most cases of megacolon are unlikely to result in significant changes in these routine laboratory tests, they need to be performed to rule out some causes or contributing factors to constipation, such as dehydration, hypokalemia (low serum potassium levels) and hypercalcemia (elevated serum calcium levels.)
Abdominal X-rays should be performed in all cats to help assess the severity of the impaction and to identify predisposing factors such as ingestion of foreign material such as bone fragments, tumors that might be obstructing the passage of feces, pelvic fractures impinging on the pelvic canal, or spinal cord abnormalities.
Careful digital rectal exam. Because cats are smaller than dogs, digital rectal exam is more difficult to perform and cats are less cooperative; sedation or anesthesia is usually required. Improper healing of a pelvic fracture, rectal foreign bodies, strictures or tumors can often be detected via digital rectal exam.
Abdominal ultrasound. This procedure is usually not necessary. However, if a tumor is impinging on the colon and impeding the passage of feces, ultrasound may help characterize the tumor further and an ultrasound-guided biopsy might be warranted.
Colonoscopy allows evaluation of the colon non-invasively using an endoscope. The inside surface of the colon can be examined for inflammatory disorders, the formation of pouches (sacculations), diverticula and strictures. Biopsies can be taken during this procedure.
Barium enema. If colonoscopy is not available, a barium enema followed by radiographs may also reveal strictures, sacculations, and diverticula. All of these can impede the passage of feces and cause constipation and its sequela, megacolon.
Complete neurologic examination. A complete neurologic examination, possibly even involving cerebrospinal fluid analysis, myelogram, which is a specialized radiographic dye study to evaluate the spinal cord, and electrophysiologic studies, which include evaluation of muscle function and nerve conduction, should be considered. These tests help to identify neurologic causes of constipation, for example, spinal cord injury, nerve trauma, or spinal cord deformity in Manx cats.
The therapy for megacolon depends on several factors including the severity of the constipation and fecal impaction and the underlying cause. Initial episodes of constipation, if mild, may not need any therapy at all. Mild or moderate episodes that recur usually require some kind of treatment. There are many treatment options. The most successful therapy usually involves a combination of treatment interventions.
Dietary modification. Fiber helps to attract water into the feces, and helps bulk up the stool. This helps ameliorate constipation to some degree. Fiber can be added to the cat’s regular diet, using products such as Metamucil, or a high fiber prescription diet (such as Hill’s W/D or R/D) or an over the counter diet (Hill’s Feline Maintenance Light Formula) can be fed. Wheat bran and canned pumpkin are other natural sources of fiber.
Enemas. Mild or moderate episodes of constipation that recur will sometimes require the administration of enemas. Although clients are often willing and able to administer a packaged enema to their cat at home, enemas are best performed in a veterinary setting. Extreme care must be taken if enemas are purchased and given at home. Certain types of enemas can have serious and potentially fatal results in cats.
Laxatives. Laxatives usually cause elimination of formed feces. There are several types of laxatives available.
Bulk forming laxatives. Most of these laxatives are dietary fiber supplements.
Emollient laxatives such as dioctyl sodium sulfosuccinate are available in oral form and in enema form. The clinical effectiveness of these laxatives are not as well documented as other laxatives.
Lubricant laxatives. Mineral oil and white petrolatum (Vaseline®) are common lubricant laxatives used to treat constipation. They tend to work better in cases of mild constipation.
Hyperosmotic laxatives. Lactulose is the best known and most effective of the hyperosmotic laxatives. Laculose is a complex carbohydrate. When it gets fermented in the colon, it stimulates the colon to secrete fluid and soften the feces, as well as stimulate propulsive motility in the colon.
Stimulant laxatives. These are laxatives that are capable of stimulating propulsive motility in the colon. Bisacodyl (Dulcolax®) is the most effective stimulant laxative in the cat.
Colonic prokinetic agents (drugs that make the colon contract). Cisapride is a drug that enhances the propulsive movements in the colon. It has been well documented to have a good effect on the colon in cats with mild or moderate megacolon. Long-standing constipation or severe megacolon is less likely to respond. This is a human pharmaceutical, and although no significant side effects have been observed in cats given cisapride, serious side effects in humans have caused the manufacturer to cease production of this drug. Two other drugs, ranitidine and nizatidine, are reported to stimulate colonic motility, and may be useful in the treatment of megacolon.
Manual extraction of feces. Cats that are unresponsive to enemas may require manual extraction of impacted feces. Cats are given fluid therapy so that they’re well hydrated, and then usually are anesthetized. The veterinarian administers warm water or saline into the colon, while breaking down the firm feces manually via the rectum, and by manipulating the colon by abdominal palpation.
Surgery. Cats that are unresponsive or poorly responsive to medical therapy may benefit from surgery. The surgery most commonly performed is called a subtotal colectomy. Cats generally have a favorable prognosis for recovery after colectomy. Postoperatively, cats will usually maintain a soft or semisolid fecal consistency that most owners find acceptable. The stress of repeated enemas and long-term laxative therapy is alleviated, and unless there are underlying disorders, most cats go on to live normal lives. An occasional cat may suffer recurrences of constipation.
Follow-up Care for Cats with Megacolon
Optimal treatment for your cat requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your cat does not rapidly improve. Administer all prescribed medication as directed. Alert your veterinarian if you are experience problems treating your cat.
Feed a diet high in fiber to bulk up the feces and help attract water to the stool, improving its consistency. Regular grooming is recommended, as impaction of the colon with ingested hair (as well as other foreign material) is a very common cause of constipation in the cat. Regular exercise has been found to help prevent or minimize recurrences of constipation and the occasional use of laxatives when excessively firm stool is noticed in the litter box may be helpful.