Hirschsprung Disease
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Direct answer
Hirschsprung disease is congenital aganglionosis of the distal bowel — neural crest cells failed to migrate into the rectum and a variable length of colon — producing functional obstruction: the aganglionic segment cannot relax, so stool cannot pass. The neonatal clues are delayed passage of meconium beyond 48 hours in a term baby, abdominal distension and bilious vomiting; the older child has severe constipation from birth with a scaphoid empty rectum on examination and, tellingly, no soiling. Diagnosis is confirmed by rectal suction biopsy showing absent ganglion cells, and the feared complication is Hirschsprung-associated enterocolitis, which remains the major cause of death.
What you must remember
- A term newborn should pass meconium within 24 hours in about 90 per cent of cases and virtually all by 48 hours — delay beyond 48 hours is the single best neonatal clue.
- Male-to-female ratio about 4:1; rectosigmoid (short-segment) disease accounts for roughly 75–80 per cent of cases.
- Associations: Down syndrome in roughly 5–10 per cent, RET and GDNF gene mutations, and Waardenburg with other neurocristopathies.
- Classic examination sign: on digital rectal examination the rectum is empty and stenosed-feeling, followed by explosive discharge of gas and stool on withdrawal — the "squirt sign".
- Contrast enema: transition zone between dilated proximal and narrow distal bowel, decreased rectosigmoid index, retained barium at 24 hours.
- Anorectal manometry shows absent rectoanal inhibitory reflex — a useful screening test in older children, but rectal biopsy remains the standard.
- Diagnostic gold standard: rectal suction biopsy at 1–2 cm (and 3–4 cm) above the dentate line showing absent ganglion cells in the submucosal plexus, hypertrophied nerve trunks and increased acetylcholinesterase activity.
- Hirschsprung-associated enterocolitis: fever, explosive foul diarrhoea, abdominal distension and sepsis, due to stasis and bacterial overgrowth; it can occur before or after surgery — treat with rectal decompression, broad-spectrum antibiotics and resuscitation.
- Definitive surgery: pull-through procedures (Swenson, Duhamel, Soave — transanal endorectal pull-through is now common), increasingly as single-stage procedures in the neonatal period; a diverting colostomy precedes pull-through in complicated or late-presenting cases.
- Distinguish from functional constipation: Hirschsprung starts from birth, has no soiling, empty rectum and failure to thrive; functional constipation has intermittency, overflow soiling and stool palpable in the rectum.
A typical exam case
A two-day-old term boy has not passed meconium at 52 hours and now has gross abdominal distension with bilious vomiting. Pass a warm rectal examination: tight lower rectum, then a gush of gas and meconium on withdrawal — relief that is temporary and diagnostic in direction. Plain radiograph shows dilated loops; resuscitate, decompress with rectal irrigation, and obtain a contrast enema demonstrating the transition zone. Confirmation is by rectal suction biopsy: no ganglion cells, hypertrophied nerve trunks. Plan a pull-through — many centres now do a primary transanal endorectal pull-through in the stable neonate — counselling that enterocolitis remains possible even after successful surgery.
The second presentation earns its own question: a three-year-old with abdominal distension, chronic constipation since the neonatal period, ribbon-like stools, poor growth and never any soiling, in whom abdominal examination finds distension but the rectum is strikingly empty. That constellation — constipation from birth plus empty rectum plus no soiling — should make you request anorectal manometry and biopsy rather than prescribing another laxative. And the emergency stem: a known Hirschsprung baby returns with fever, explosive diarrhoea and a distended, tender abdomen — enterocolitis, needing fluids, broad-spectrum antibiotics, decompression, gentle rectal irrigation and urgent surgical review, because perforation and toxic megacolon kill.
Where students slip
The recurring errors are shortcut errors. First, treating barium enema or the transition zone as diagnostic — radiology suggests, but only biopsy proves, and a transition zone may be absent in long-segment disease or misleading in enterocolitis. Second, forgetting the biopsy level: sampling too low or too high gives false negatives because of the normal hypoganglionic zone within a centimetre of the dentate line. Third, missing soiling logic in the older child — functional constipation produces overflow soiling while Hirschsprung does not, and inverting that relationship costs the mark. And candidates who counsel "surgery cures everything" forget post-pull-through enterocolitis and persistent constipation, which dominate follow-up questions in viva.
Frequently asked questions
Which finding in a term newborn most strongly suggests Hirschsprung disease?
Failure to pass meconium within 48 hours of birth — the vast majority of term infants pass meconium in the first day, so delay demands evaluation alongside distension and vomiting.
What is the confirmatory diagnostic test?
Rectal suction biopsy showing absent submucosal ganglion cells with hypertrophied nerve trunks and increased acetylcholinesterase staining, taken 1–2 cm above the dentate line.
How does Hirschsprung-associated enterocolitis present?
With fever, abdominal distension and explosive, often bloody diarrhoea due to stasis and bacterial overgrowth; it is the leading cause of death, may precede or follow surgery, and needs antibiotics with rectal decompression.
Which type of Hirschsprung disease is most common?
Short-segment disease confined to the rectosigmoid in about three-quarters of cases, with a male predominance of about 4:1.