Acute and chronic megacolon

Abstract

Megacolon, defined as dilation of the abdominal colon, may occur acutely or in a chronic form. Acute megacolon that occurs in association with severe inflammation of the colon is known as toxic megacolon, whereas acute megacolon without obvious colonic disease is known as Ogilvie's syndrome. The pathophysiology and management of toxic megacolon, Ogilvie's syndrome, and chronic megacolon in adults differ significantly, and it is critically important to distinguish among these entities. Toxic megacolon is a medical emergency that requires coordinated intensive medical and surgical management. In addition to vigorous resuscitation with fluids, electrolytes, and blood products, medical treatment consists of parenteral corticosteroids, broad-spectrum antibiotics, and close monitoring of the patient. Surgical intervention is required if there is no improvement, or deterioration after 12 to 24 hours of intensive medical management, or if there is evidence of colon perforation. Ogilvie's syndrome usually occurs in hospitalized patients with serious underlying medical or surgical illnesses. Management is directed at preventing ischemia and perforation of the distended colon. Supportive therapy includes nasogastric suction, correction of fluid and electrolyte imbalances, stopping potentially aggravating medications, and decompressing the colon with a rectal tube and positional changes. Intravenous neostigmine is the only pharmacologic agent of proven efficacy; colonoscopic decompression is an alternative in patients who do not respond to neostigmine or who have conditions that contraindicate its use. Daily oral administration of polyethylene glycol electrolyte solutions appears to decrease the relapse rate after initial decompression is achieved. Chronic megacolon in adults represents advanced colon failure that does not respond to pharmacologic stimulation. Goals of therapy are to cleanse the colon, prevent impaction, and minimize stool volume and gas buildup. For patients with disabling symptoms, surgical exclusion of the colon, decompression and antegrade enemas via cecostomy, or subtotal or segmental resection may be palliative.