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.Diagnosis In-depth 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.