# Hirschsprung Disease > NEET-PG Surgery notes on Hirschsprung disease: aganglionosis, suction rectal biopsy, absent RAIR, Swenson Duhamel Soave pull-throughs and enterocolitis. - Canonical URL: https://prepelephant.com/topics/neet-pg/surgery/hirschsprung-disease - Exam / course: NEET-PG · Subject: Surgery - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Hirschsprung Disease", PrepElephant, https://prepelephant.com/topics/neet-pg/surgery/hirschsprung-disease ## Direct answer Hirschsprung disease is congenital aganglionosis of the distal bowel from failure of neural crest migration, producing a tonically contracted segment with proximal functional obstruction and megacolon. The flag in a term neonate is delayed passage of meconium beyond 48 hours with distension and bilious vomiting; older infants and children show chronic constipation, failure to thrive and a child who has never soiled. Diagnosis is by suction rectal biopsy — absent ganglion cells, hypertrophic nerve trunks, raised acetylcholinesterase — supported by anorectal manometry showing absence of the rectoanal inhibitory reflex. Definitive treatment is a pull-through operation — Swenson, Duhamel or Soave — after stabilisation, with Hirschsprung-associated enterocolitis the principal cause of death. ## What you must remember - **Genetics and epidemiology:** incidence around 1 in 5000 live births, male predominance roughly 4:1; RET proto-oncogene variants account for a share of cases, and about 5-10% have Down syndrome. - **Length of disease:** rectosigmoid (short segment) in about 75-80%, long-segment colonic disease around 10%, total colonic aganglionosis in 5-8% — the length defines the operation. - **Diagnostic gold standard:** suction rectal biopsy taken at least 1 cm above the dentate line (the distal 1 cm is physiologically hypoganglionic), showing absent submucosal ganglion cells, hypertrophied nerve trunks and raised acetylcholinesterase. - **Screening test:** anorectal manometry with absent rectoanal inhibitory reflex (no internal sphincter relaxation on rectal balloon distension). - **Barium enema:** shows the funnels-shaped transition zone between dilated ganglionic colon and narrow aganglionic rectum, but may be unhelpful in small neonates. - **Operations:** Swenson (endorectal-free pull-through and direct anastomosis), Duhamel (retrorectal pull-through leaving an aganglionic- plus ganglionic side-to-side pouch), Soave (endorectal mucosectomy pull-through within the aganglionic muscular cuff); all now often performed transanally, with or without a preliminary levelling colostomy. - **Levelling colostomy:** the stoma is sited on ganglionic bowel confirmed by intraoperative frozen-section biopsy. - **Enterocolitis (HAEC):** fever, explosive diarrhoea (often paradoxically bloody) and a toxic distended abdomen, before or after pull-through — treated with rectal washouts, decompression, broad-spectrum antibiotics and metronidazole; the leading killer. ## Confirming the diagnosis, then correcting it Sequence the pathway as the examiners do. A term baby has not passed meconium at 50 hours; a finger stimulus or gentle rectal examination triggers an explosive release of gas and meconium — the classic immediate clue — and the baby returns with distension within days. Anorectal manometry shows no relaxation of the internal sphincter on balloon inflation: absent RAIR. Suction rectal biopsy at 1, 2 and 3 cm above the dentate line shows no ganglion cells and thick acetylcholinesterase-positive trunks: diagnosis closed. A contrast enema maps the transition zone but never overrides histology. Correction may be staged or primary: the modern default is a primary transanal pull-through in a well baby, with a levelling colostomy reserved for late presentation, enterocolitis, malnutrition or a long segment — the colostomy level chosen on frozen section, because pulling through aganglionic bowel is the catastrophe of this surgery. Family counselling covers the recurrence risk in siblings and the long-run expectations of soiling and constipation, which persist for a substantial minority. ## Where marks are lost The first error is biopsy depth: sampling within 1 cm of the dentate line reads "aganglionic" in a normal child because that zone is physiologically hypoganglionic, and the false positive lands a healthy baby in theatre. The second is trusting the neonatal contrast enema — a transition zone may be absent in the first weeks, so a normal enema never excludes the disease when histology is pending. The third is misreading enterocolitis as simple gastroenteritis: a post-pull-through child with fever and foul diarrhoea has HAEC until washouts and antibiotics say otherwise, and a plain film may show the jagged mucosal "saw-tooth" outline of the aganglionic segment. The fourth confuses the operations — remember them by their different failures: Swenson's pelvic dissection risks continence nerves, Duhamel leaves a blind spurring pouch with faecal stasis, Soave leaves a muscular cuff that can stricture. Finally, total colonic aganglionosis is the answer to the "baby with normal rectal biopsy but whole-bowel dilatation" variant — level of disease above the sampled segment. ## Frequently asked questions ### Which investigation is the gold standard for Hirschsprung disease? Suction rectal biopsy at least 1 cm above the dentate line, showing absent ganglion cells with hypertrophic acetylcholinesterase-positive nerve trunks. ### What does anorectal manometry show in Hirschsprung disease? Absence of the rectoanal inhibitory reflex — the internal anal sphincter fails to relax on rectal balloon distension — making it a useful screening test. ### Which finding raises suspicion in a neonate? Failure to pass meconium within 48 hours of birth in a term infant, often with explosive discharge after rectal stimulation. ### What is Hirschsprung-associated enterocolitis? The life-threatening complication of abdominal distension, fever and foul often-bloody diarrhoea from stasis and bacterial overgrowth, treated with washouts, decompression and antibiotics. ### How do the Swenson, Duhamel and Soave operations differ? Swenson resects the aganglionic segment and anastomoses colon to the low rectum, Duhamel pulls ganglionic colon through a retrorectal track, and Soave pulls it through a mucosectomised aganglionic cuff.