megacolon

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Related to mega colon: Hirschsprung disease, toxic megacolon

megacolon

 [meg″ah-ko´lon]
dilatation and hypertrophy of the colon.
Megacolon. From McKinney et al., 2000
acquired megacolon colonic enlargement associated with chronic constipation, but with normal ganglion cell innervation.
acute megacolon toxic megacolon.
aganglionic megacolon (congenital megacolon) Hirschsprung's disease.
toxic megacolon acute dilatation of the colon associated with amebic dysentery or ulcerative colitis; called also acute megacolon.

meg·a·co·lon

(meg'ă-kō'lon),
A condition of extreme dilation of the colon.
Synonym(s): giant colon

megacolon

(mĕg′ə-kō′lən)
n.
Extreme dilation and hypertrophy of the colon.

megacolon

A massively distended colon with decreased peristaltic activity, due to defective innervation (congenital), intraluminal overgrowth of microorganisms or of psychogenic origin.

Clinical findings
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
Symptoms eliminated in ± 90% of patients with surgery; outcomes better with early intervention.

Megacolon—Congenital and Acquired
Congenital (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 and Laurence-Moon-Biedl syndrome.
 
Pathology
In affected regions the colon is narrowed and the intramural ganglion cells are absent in both the submucosal (Meissner’s) and myenteric (Auerbach’s plexi).
 
Molecular genetics
Megacolon is associated with mutations in the RET gene.
 
Management
Resection of aganglionic colon.
 
Acquired
A condition related to narcotics or disruption of ganglionic innervation (e.g., 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. It may be due to intraluminal overgrowth of microorganisms in Crohn’s disease and ulcerative colitis (toxic megacolon), characterised by mucosal necrosis, transmural inflammation and systemic toxicity with high fever, tachycardia, leukocytosis and diarrhoea.

In psychogenic megacolon, no radiologic or pathologic defects are present; it  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.

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  

meg·a·co·lon

(meg'ă-kō-lŏn)
A condition of extreme dilation and hypertrophy of the colon.

megacolon

Enlargement (hypertrophy) and widening (dilation) of part or all of the COLON associated with severe and intractable CONSTIPATION. Megacolon may be CONGENITAL or acquired. Congenital megacolon is an AUTOSOMAL RECESSIVE condition caused by the local absence of the nerves responsible for PERISTALSIS.

Megacolon

Dilation of the colon.

meg·a·co·lon

(meg'ă-kō-lŏn)
Condition involving extreme dilation of the colon.