Megacolon
Congenital Megacolon (Hirschprung’s disease)
•Megacolon= larger colon
•Dolicocolon= longer colon
•HD is characterized by the absence of myenteric and submucosal ganglion cells in the
distal alimentary tract;
•decreased motility in the affected bowel segment
Frequency
•Approximately 1 per 5000 live births.
•Sex: 4 times more common in malesthan females.
•Age:
–Nearly all children with Hirschsprung disease are diagnosed during the first 2 years of
life.
–one half are diagnosed before they are aged 1 year.
–Minority not recognized until later in childhood or adulthood.
•Mortality/Morbidity:
1
, –The overall mortality of Hirschsprung enterocolitis is 25-30%, which accounts for almost
all of the mortality from Hirschsprung disease.
Pathophysiology
•Absence of parasympathetic ganglion cells in the myenteric and submucosal plexus of
the rectum and/or colon.
•Failure of migration of neuroblasts into the gut from vagal nerve trunks at the end of
the first trimester of fetal life. (proximal colon by 8 weeks and in the rectum by 12
weeks)
•Arrest in migration leads to an aganglionic segment.
•Loss of ganglion cells extends for a variable distance above the anorectal junction.
•This absence of normal parasympathetic innervation prevents gut peristalsis, leading to
functional constipation.
•The proximal colon hypertrophied by trying to overcome functional obstruction.
•Transitional zone exists between normal and abnormal aganglionic intestine.
•Failure of the internal sphincter to relax with rectal distention is pathognomonic.
•Acetylcholine concentrations in aganglionic segments are threefold lower than in
ganglionic segments
HD can be classified by the extension of the aganglionosis as
follows:
Classical HD (75% of cases): Rectosigmoid
Long segment HD (20% of cases)
Total colonic aganglionosis (3-12% of cases)
Rare variants include the following:
–Total intestinal aganglionosis
–Ultra-short-segment HD (involving the distal rectum below the pelvic floor and the anus)
Clinical presentation:
•Newborns:
–Failure to pass meconium within the first 48 hours of life
2
Congenital Megacolon (Hirschprung’s disease)
•Megacolon= larger colon
•Dolicocolon= longer colon
•HD is characterized by the absence of myenteric and submucosal ganglion cells in the
distal alimentary tract;
•decreased motility in the affected bowel segment
Frequency
•Approximately 1 per 5000 live births.
•Sex: 4 times more common in malesthan females.
•Age:
–Nearly all children with Hirschsprung disease are diagnosed during the first 2 years of
life.
–one half are diagnosed before they are aged 1 year.
–Minority not recognized until later in childhood or adulthood.
•Mortality/Morbidity:
1
, –The overall mortality of Hirschsprung enterocolitis is 25-30%, which accounts for almost
all of the mortality from Hirschsprung disease.
Pathophysiology
•Absence of parasympathetic ganglion cells in the myenteric and submucosal plexus of
the rectum and/or colon.
•Failure of migration of neuroblasts into the gut from vagal nerve trunks at the end of
the first trimester of fetal life. (proximal colon by 8 weeks and in the rectum by 12
weeks)
•Arrest in migration leads to an aganglionic segment.
•Loss of ganglion cells extends for a variable distance above the anorectal junction.
•This absence of normal parasympathetic innervation prevents gut peristalsis, leading to
functional constipation.
•The proximal colon hypertrophied by trying to overcome functional obstruction.
•Transitional zone exists between normal and abnormal aganglionic intestine.
•Failure of the internal sphincter to relax with rectal distention is pathognomonic.
•Acetylcholine concentrations in aganglionic segments are threefold lower than in
ganglionic segments
HD can be classified by the extension of the aganglionosis as
follows:
Classical HD (75% of cases): Rectosigmoid
Long segment HD (20% of cases)
Total colonic aganglionosis (3-12% of cases)
Rare variants include the following:
–Total intestinal aganglionosis
–Ultra-short-segment HD (involving the distal rectum below the pelvic floor and the anus)
Clinical presentation:
•Newborns:
–Failure to pass meconium within the first 48 hours of life
2
