megacolon

A condition of extreme dilation of the colon. SYN: giant colon.

- acquired m. m. occurring on the basis of an acquired disease; occurs in inflammatory bowel disease (toxic m.) and Chagas disease (South American trypanosomiasis).

- congenital m., m. congenitum congenital dilation and hypertrophy of the colon due to absence (aganglionosis) or marked reduction (hypoganglionosis) in the number of ganglion cells of the myenteric plexus of the rectum and a varying but continuous length of gut above the rectum; also seen in dogs. SYN: Hirschsprung disease.

- idiopathic m. an acquired m., found in children and adults, without distal obstruction or absence of ganglion cells; the muscle of the dilated colon is thin.

- toxic m. acute nonobstructive dilation of the colon, seen in fulminating ulcerative colitis and Crohn disease.

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mega·co·lon 'meg-ə-.kō-lən n extreme dilation of the colon that may be congenital or acquired see HIRSCHSPRUNG'S DISEASE

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n.

dilatation, and sometimes lengthening, of the colon. It is caused by obstruction of the colon, Hirschsprung's disease, or longstanding constipation, or it may occur as a complication of ulcerative colitis (toxic megacolon).

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mega·co·lon (meg″ə-koґlən) an abnormally large or dilated colon; the condition may be congenital or acquired, acute or chronic. Called also macrocolon.