congenital megacolon


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Related to congenital megacolon: fever blister, congenital aganglionic 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.

con·gen·i·tal meg·a·co·lon

, megacolon 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; seen in humans and dogs.

congenital megacolon

Hirschsprung disease

A condition of infant onset characterised by the absence of myenteric nerves in the distal colon, extending proximally from the anus for a variable distance. It affects an estimated 1:5000 live births, and is more common in males (male:female ratio, 4:1); up to 10% have Down syndrome. 

Clinical findings
Failure to pass meconium or stool in first 24 hours post-partum; abdominal distention; vomiting; constipation at birth. Peristalsis is absent in aganglionic segment, causing proximal pseudo-obstruction and gross dilatation, enterocolitis and perforation. In older children, Hirschsprung disease is characterised by chronic constipation, abdominal distention and stunted growth.

Diagnosis
By rectal suction biopsy; must include submucosa, taken at least 2 cm above pectinate line.

Management
Resection of aganglionic segment, guided by intraoperative frozen sections from myenteric plexus.

congenital megacolon

1. Hirschsprung's disease.
2. Megacolon, see there.

con·gen·i·tal meg·a·co·lon

, megacolon congenitum (kŏn-jen'i-tăl meg'ă-kō-lŏn, kon-jen'i-tŭm)
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 colon above the rectum.
Synonym(s): Hirschsprung disease.

Hirschsprung,

Harald, Danish physician, 1830-1916.
Hirschsprung disease - congenital dilation and hypertrophy of the colon. Synonym(s): congenital megacolon

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.
Enlarge picture
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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