megacolon /meg″əkōlən/ [Gk, megas + kolon, colon] , abnormal massive dilation of the colon that may be congenital, toxic, or acquired. Congenital megacolon (Hirschsprung’s disease) is caused by the absence of autonomic ganglia in the smooth muscle wall of the colon. Toxic megacolon is a grave complication of ulcerative colitis and may cause perforation of the colon, septicemia, and death. Colonoscopy and surgery are the usual treatments for toxic and congenital megacolon. Acquired megacolon is the result of a chronic refusal to defecate, which usually occurs in children who are psychotic or cognitively impaired. The colon becomes dilated by an accumulation of impacted feces. Laxatives, enemas, and psychiatric treatment are often necessary. See also Hirschsprung’s disease.
