Congenital diseases of the colon. Hirschsprung’s disease
OVERVIEW AND HIRSCHSPRUNG DEFINITION
Congenital colonic disorders include Hirschsprung’s disease, congenital megacolon, intestinal malrotation with colonic involvement, congenital stenosis/atresia and rare duplication anomalies. Hirschsprung’s disease is congenital absence of ganglion cells in the submucosal (Meissner) and myenteric (Auerbach) plexuses of a distal bowel segment, causing failure of relaxation and functional obstruction.
EMBRYOLOGY AND PATHOPHYSIOLOGY
Enteric neural crest cells migrate caudally during development. Failure of migration, survival or differentiation leaves a distal aganglionic segment, most commonly rectosigmoid. The aganglionic bowel remains tonically contracted; proximal normally innervated bowel becomes dilated and hypertrophied. The transition zone separates narrow distal bowel from dilated proximal colon. Disease may be short-segment, long-segment or total colonic.
CLINICAL FEATURES
Newborns classically fail to pass meconium within 24–48 hours, develop abdominal distension and bilious vomiting. Passage of explosive stool and gas after rectal examination is a classic but not definitive sign. Older children may present with chronic constipation, abdominal distension, poor growth and dependence on enemas. Hirschsprung-associated enterocolitis is a life-threatening complication with fever, diarrhoea (sometimes explosive/foul), distension, lethargy and sepsis.
DIAGNOSIS
Plain abdominal radiograph may show dilated bowel and distal gas paucity. Contrast enema can demonstrate a narrow distal segment, transition zone and reversed rectosigmoid ratio; it is not definitive, especially in neonates. Anorectal manometry may show absence of the rectoanal inhibitory reflex. Rectal suction biopsy is the diagnostic gold standard and demonstrates absence of ganglion cells, hypertrophic nerve trunks and supportive histochemical/immunohistochemical findings. Biopsy must be taken above the physiologic distal aganglionic zone.
MANAGEMENT
Initial care includes bowel decompression, rectal irrigations, fluid/electrolyte correction and nutritional support. Treat enterocolitis urgently with IV fluids, broad-spectrum antibiotics, bowel rest and rectal irrigations; severe cases need intensive care and possible diversion. Definitive treatment is pull-through surgery, removing or bypassing aganglionic bowel and bringing normally ganglionated bowel to the anus (Swenson, Soave or Duhamel techniques; often minimally invasive). A stoma may be required in unstable, very ill or extensive disease. Confirm normal ganglion cells at the proximal margin.
COMPLICATIONS AND FOLLOW-UP
Complications include enterocolitis, perforation, failure to thrive, constipation, soiling, anastomotic leak, stricture, cuff obstruction and persistent dysmotility. Long-term follow-up assesses bowel function, growth, continence and recurrent enterocolitis.