megacolon /mega·co·lon/ (meg´ah-ko″lon) dilatation and hypertrophy of the colon.
acquired megacolon colonic enlargement associated with chronic constipation, but with normal ganglion cell innervation.
aganglionic megacolon , congenital megacolon Hirschsprung's disease; that due to congenital lack of myenteric ganglion cells in a segment of the large bowel, with loss of motor function in that segment and massive dilatation of the colon proximally.
idiopathic megacolon acquired m.
toxic megacolon that associated with amebic or ulcerative colitis.
| idiopathic megacolon n. Megacolon resulting in constipation, associated with faulty bowel habits and thin musculature of the colon. |
megacolon
dilatation and hypertrophy of the colon.
acquired megacolon
colonic enlargement associated with chronic constipation, but with normal ganglion cell innervation. Most common in dogs and cats, the usual causes are dietary factors, lack of exercise, prostatic enlargement, anal disease and neurological deficits.
aganglionic megacolon
due to congenital absence of myenteric ganglion cells and abnormal motor activity in a distal segment of the large bowel. There is continuous spasm in the aganglionic segment that causes a stenosis, and a massive distention of the normal proximal colon develops secondarily. The disease in humans is called Hirschsprung's disease and a similar, but not identical, condition occurs in piebald mice and Overo horses. Congenital megacolon may occur in dogs and cats, but acquired disease is much more common. Called also congenital megacolon.
congenital megacolon
see aganglionic megacolon (above).
idiopathic megacolon
recurrent episodes of constipation in aging cats over a long period of time is believed to lead to the progressive development of a dilated colon.
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Barium enema in an aged cat with idiopathic megacolon. By permission from Ettinger SJ, Feldman E, Textbook of Veterinary Internal Medicine, Saunders, 2004
inherited megacolon
is presumed in fattening pigs in which there is abdominal distention and wasting without rectal stricture.
psychogenic megacolon
seen in cats and dogs that will not defecate indoors. Prolonged fecal retention causes loss of the defecation reflex, especially in aged patients.
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