Megacolon is the result of decreased motility and irreversible dilation of the large intestine. It may be a consequence of recurring episodes of constipation or obstipation.  The underlying cause of megacolon can be idiopathic or it can be acquired due to numerous other disease processes.   

History

Megacolon can be observed in cats of any age, sex, or breed.  Patients usually present for reduced, absent, or painful defecation for a period of time ranging from days to weeks or months. Cats with low physical activity, painful conditions that prevent squatting to defecate, and Manx cats may be at increased risk for developing megacolon.

Clinical signs are usually chronic and/or recurrent for months to years and include:

• Straining with small or no fecal output        

• Small amounts of diarrhea/mucous

• Intermittent blood in feces                           

• Vomiting/anorexia/weight loss

• Hard, dry feces                                            

• Infrequent defecation

Diagnosis

The first step to diagnosis is a physical examination which will reveal colonic impaction. Dehydration and abdominal pain may also be present.  Additional testing is needed to determine the cause and the best treatment.

These tests may include:

1.      Neurologic exam

2.      Blood tests  (CBC, Metabolic profile)

3.      Radiographs of the abdomen

4.      Rectal examination under general anesthesia

5.      Endoscopy/colonoscopy, ultrasound, barium contrast studies, or CT/MRI

Treatment

The specific therapeutic plan will depend on underlying cause, but initial medical management is designed to restore hydration, correct metabolic abnormalities and relieve the colonic impaction.   The patient is hospitalized and placed on intravenous fluids; then warm water enemas are administered as needed to soften the feces.  Most patients receive oral laxatives and medication to stimulate colonic motility. For some patients general anesthesia and manual extraction of feces may be necessary. Treatment over several days may be required to remove the fecal mass. Specific therapy is directed at correcting predisposing factors and preventing recurrence.  When megacolon is unresponsive to medical management, surgery will be needed. The kitty will be referred to a boarded veterinary surgeon for a subtotal colectomy.

Management is life-long and consists of daily administration of laxative medication, motility modifying agents, and special low residue diets.  Clean litter should be provided at all times to encourage regular defection, long-hair cats should be groomed to remove loose hair before it is ingested, ingestion of constipating/abrasive material should be prevented and physical activity encouraged.

The prognosis is guarded for medical management of this disease.  Treatment is life-long and can be frustrating since recurrent constipation/obstipation is common.  Surgery is the only other option if medical treatment is unsuccessful.