megacolon

megacolon /mega·co·lon/ (meg´ah-ko″lon) dilatation and hypertrophy of the colon.

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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.

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meg·a·co·lon (mg-kln)

n.

Extreme dilation and hypertrophy of the colon.

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Megacolon

Dilation of the colon.

Mentioned in: Hirschsprung's Disease

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megacolon

[meg′əkōlən]

Etymology: 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 mentally retarded. The colon becomes dilated by an accumulation of impacted feces. Laxatives, enemas, and psychiatric treatment are often necessary.

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megacolon

(meg´kō´ln),
n an abnormal dilation of the colon that may be congenital, toxic, or acquired.

megacolon, acquired,

n a result of a chronic refusal to defecate, usually occurring in children who are psychotic or mentally retarded.

megacolon, congenital,

n caused by the absence of autonomic ganglia in the smooth muscle wall of the colon.

megacolon, toxic,

n a serious complication of ulcerative colitis that may result in perforation of the colon, septicemia, and death.

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megacolon

dilatation and hypertrophy of the colon.

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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.

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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megacolon

A massively distended colon with ↓ activity, due to defective innervation–congenital, intraluminal overgrowth of microorganisms or of psychogenic origin Clinical Intestinal obstruction, constipation, vomiting, abdominal distension, poor weight gain, retarded growth Management Temporary colostomy for bowel rest, followed by resection of affected bowel segment Prognosis Sx eliminated in ± 90% of Pts with surgery; outcomes better with early intervention

Megacolon

Congenital megacolon Congenital aganglionosis, Hirschsprung's disease A disease affecting 1:5000 live births, with a sibling risk of 1% for girls and 5% for boys; Hirschsprung's disease–HD is ten-fold more common in Down syndrome; other anomalies in HD include hydrocephalus, VSD, cryptorchism, diverticulosis of the urinary bladder, renal cysts and agenesis, polyposis coli, Laurence-Moon-Biedl syndrome Treatment Resection of aganglionic colon

Acquired megacolon A condition related to narcotics or disruption of ganglionic innervation–eg idiopathic hypomotility, neuropathies–parkinsonism, multiple sclerosis, myotonic dystrophy, diabetic neuropathy, Chagas' disease, smooth muscle disorders–amyloidosis and progressive systemic sclerosis and metabolic disease–hypokalemia, lead poisoning, porphyria, pheochromocytoma, hypothyroidism and may be due to intraluminal overgrowth of microorganisms in Crohn's disease and ulcerative colitis–toxic megacolon–characterized by mucosal necrosis, transmural inflammation and systemic 'toxicity' associated with high fever, tachycardia, leukocytosis and diarrhea; in psychogenic megacolon, no radiologic or pathologic defects are present–the condition may be related to a 'fixation' in Freud's anal retentive stage of psychosexual development, with constipation of later onset than in HD, possibly 2º to abuse of anthracine laxatives