Megacolon in Cats


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
  • Painful 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
  • Chemistry panel
  • Urinalysis
  • Abdominal x-rays
  • Careful digital rectal exam
  • Ultrasound
  • Colonoscopy
  • Barium enema
  • Neurological tests
  • 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)
  • Enemas
  • Bulk-forming laxatives
  • Emollient laxatives
  • Lubricant laxatives
  • Hyperosmotic laxatives
  • Stimulant laxatives
  • Drugs that make the colon contract
  • Manual extraction of feces
  • Surgery
  • 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.

    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.
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