Additional pediatric resources: GeneralPediatrics.com | PediatricEducation.org | SearchingPediatrics.com
Michael P. D'Alessandro, M.D.
Peer Review Status: Internally Peer Reviewed
Etiology/Pathophysiology:
Large bowel obstruction due to congenital absence of ganglion cells
in the myenteric plexus of the colon starting at a transition point
and extending all the way to the rectum. Peristaltic waves cannot
pass beyond this transition point which leads to a functional
obstruction. The transition zone is seen most frequently in the
rectosigmoid region, in 70% of cases, but it can be seen in the small
bowel. Five to ten percent of cases involve the entire colon and are
called total colonic Hirschsprung disease. The most serious
complication is enterocolitis which has progressive colonic dilation
with decreased ileal and colonic fluid resorption, stasis with
bacterial overgrowth and mucosal ischemia which can progress to acute
fluid loss into the bowel with diarrhea and dehydration leading to
shock, anuria and death. A high percentage (17-28%) of children with
Hirschsprung disease develop enterocolitis.
Pathology:
The definitive diagnosis is made by a full thickness rectal biopsy
which shows a lack of ganglion cells in the myenteric plexus of the
colon.
Imaging Findings:
The plain film may show multiple dilated loops of small bowel with
air fluid levels. The radiographic diagnosis is made by demonstrating
the transition zone, but this may not be possible in the newborn
because it takes weeks for the bowel to dilate. The aganglionic
segment is of normal caliber without stricture or constriction. The
normally innervated bowel is dilated above the transition zone.
In total colonic Hirschsprung's Disease, the colon is of a normal caliber and no transition zone is identified within it. The colon may appear somewhat foreshortened with a loss of the normal sigmoid redundancy, and the ileum is markedly dilated as this is where the transition zone is.
In Hirschsprung's enterocolitis, the colon is dilated, and pneumatosis may be present. Enemas should be avoided during bouts of enterocolitis because of the possibility of perforating the colon.
DDX:
Low Bowel Obstruction in a Newborn
References:
Additional pediatric resources: GeneralPediatrics.com | PediatricEducation.org | SearchingPediatrics.com
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