Hirschsprung disease — structured clinical encounter

Station 1 — recognition

The baby is 54 hours old and has not passed meconium. His abdomen is soft but distended, and he has features of Down syndrome. The combination of delayed meconium beyond 48 hours, abdominal distension and trisomy 21 puts this child at very high risk of Hirschsprung disease. Approximately 90 per cent of term neonates with Hirschsprung disease have delayed meconium beyond 48 hours, and roughly 10 per cent of all Hirschsprung patients have trisomy 21. The pre-test probability is therefore substantially elevated. I would assess and stabilise the child and arrange a suction rectal biopsy as the gold-standard diagnostic test. [1] [12]

Station 2 — investigation

You arrange investigations. The plain film shows distended loops with absent rectal gas. The contrast enema shows a narrowed distal rectosigmoid with a possible transition zone. The contrast enema finding of a narrowed distal segment with a transition zone is consistent with but not diagnostic of Hirschsprung disease. The transition zone on imaging is only approximately 70 per cent accurate at predicting the level of aganglionosis. The definitive investigation is the suction rectal biopsy, which samples mucosa and submucosa 1 to 3 cm above the dentate line. Histology with calretinin staining will show absent ganglion cells and absent calretinin if the diagnosis is confirmed. I would not rely on the contrast enema alone. [5] [10]

Station 3 — initial management

While awaiting the biopsy result, I keep the child nil by mouth, establish intravenous access and give maintenance fluids. I pass a nasogastric tube on free drainage for decompression. I start regular rectal washouts with warm normal saline to decompress the bowel, which reduces the risk of preoperative enterocolitis by clearing the stasis that drives bacterial overgrowth. I involve the paediatric surgical team and begin planning for definitive surgery. I also check the child for cardiac and other anomalies associated with trisomy 21. [1] [2]

Station 4 — definitive surgery

The biopsy confirms short-segment Hirschsprung disease. The surgical team plans a primary transanal Soave pull-through. The principle is to resect or bypass the aganglionic bowel and bring ganglionic bowel to the anal canal. In the Soave procedure, the mucosa and submucosa of the aganglionic rectum are removed, leaving the outer muscular wall as a sleeve, and the ganglionic colon is pulled through this sleeve and anastomosed at the anal verge. At operation, frozen-section levelling biopsies confirm the presence of ganglion cells at the anastomotic level. A primary neonatal transanal pull-through avoids a stoma and a second operation, and is the standard approach for uncomplicated short-segment disease. [9] [1]

Station 5 — complications and safety-netting

The parents ask what could go wrong and what signs to watch for after surgery. The most important complication to warn about is Hirschsprung-associated enterocolitis, which can occur even after a successful pull-through. I would teach the parents the warning signs: fever, abdominal distension, lethargy, poor feeding and explosive foul-smelling diarrhoea. If any of these occur they must seek urgent medical review, as enterocolitis is the leading cause of death. I would also discuss the possibility of persistent constipation or obstructive symptoms, which may need botulinum toxin injection of the internal anal sphincter. In the long term, a significant minority of children have persistent bowel dysfunction including soiling, and ongoing follow-up is essential. I would also offer genetic counselling for the family given the heritable component of the condition. [2] [9]