Hirschsprung`s disease (Aganglionic Megacolon)
Is a congenital anomaly characterized by partial to complete colonic obstruction associated with the absence of intramural ganglion cells in the distal alimentary tract, the aganglianosis may extend proximally to involve the entire colon and indeed the entire alimentary tract exclusive the stomach.Any newborn presenting with delayed passage of meconium for more than 24hours should be considered as having Hirschsprung`s disease until proved other wise.
Incidence:
Is 1:5000
M:F = 4:1
There is familial incidence in 6 % of cases.
Aetiolology :
The etiology of Hirschsprung disease is unknown.
The disease is due to absence of ganglia in the submucous and inter muscular plexuses .
The affected segment of bowel is spastic & narrow; the normally ganglionic colon proximal to it is markedly dilated.
Clinical features
The problem starts since birth. There is delayed passage of meconium. The mother notices that the infant is suffering from chronic constipation. Defecation occurs every few days or only after insertion of suppository or doing an enema.
Progressive abdominal distension develops.
Sometimes chronic intestinal obstruction culminates into acute obstruction with sever abdominal distension, absolute constipation and there may be vomiting.the most serious complication in the neonatal period is ischaemic entero colitis. The abdomen distended tensely within a few hours and the child vomits profusely while passing large amount of foul smelling gas and loose stools which may be bloody. During the attack the patient develop pyrexia and abdominal distension, the lesion is ischemic necrosis of the mucosa of the bowel above the aganglionic segment, often extending to small bowel.
Least common acute mode of presentation is with intestinal perforation.
Delayed growth and development.
Digital rectal examination reveals an narrow empty rectum and when the finger is removed, it is followed by a sudden gush of gasses or stools.
Investigations
Plain abdominal X ray reveals large bowel obstruction. In the first few days of life, colonic distention with absence of air in the rectum in plain abdominal x-ray is suggestive of Hirschsprungs, disease.Barium enema needs to be done without preparation and a small amount of barium is administered. It usually shows the narrowed aganglionic segment, followed by a dilated normal ganglionic bowel. Barium retention in the colon for 2 3 days may be the only suggestive sign of the disease in infancy, in old children, an easily identifiable transition zone is usually apparent. .Its diagnostic accuracy is 80%.
There is no substitute for a tissue diagnosis .
Rectal biopsy. Previously full thickness rectal biopsy was recommended, but now a day only a small segment of the mucosa and submucosa is taken by special forceps. Ganglion cell in the submucous layer are absent. Various methods of obtaining biopsies have been described .Suction biopsy instruments are widely used in young infants but we have found the use of punch biopsy forceps to be preferable in older children .
Anorectal manometry reveals failure of relaxation of the anal sphincters in response to rectal distension.
Treatment
Patients presenting by intestinal obstruction
Initial conservative treatment by nasogastric tube suction, I.V. fluids and repeated colonic washouts with saline .
If the obstruction is relieved, prepare the patient for later elective surgery.
If the obstruction is not relieved perform urgent colostomy.
Patient without obstruction require elective surgery(pull-through operation).
Surgery is ideally performed at the age of 6-9 months.Definitive surgery for Hirschsprungs disease entails complete excision of the aganglionic segment of the bowel up to 4 inches above the funnel and then anastomosis of the normal colon to the lower half of the anal canal (pull_through).
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