Hirschsprung disease — branching viva

Opening — framing the problem

The examiner begins: a full-term male neonate has not passed meconium at 52 hours. He is feeding poorly and his abdomen is distended. What is your first thought? [1]

My first thought is that failure to pass meconium within 48 hours in a term neonate is abnormal, and the combination with distension and poor feeding points to a low intestinal obstruction. The diagnosis I must exclude is Hirschsprung disease, because missing it risks the child developing Hirschsprung-associated enterocolitis, which is the leading cause of death. I would assess and stabilise the child and arrange a suction rectal biopsy. [1] [6]

Branch A — the pathophysiology

Why does the aganglionic bowel obstruct? What goes wrong in development? [12]

During weeks 5 to 12 of gestation, neural crest cells migrate craniocaudally along the developing gut to form the enteric ganglion cell plexuses. When migration stalls before it reaches the anal canal, the distal bowel is left aganglionic. The aganglionic segment lacks inhibitory interneurons and cannot relax ahead of a peristaltic wave, so it stays tonically contracted and behaves like a fixed obstruction. Stool and gas accumulate proximally, causing dilation and hypertrophy of the ganglionic bowel. [12]

Branch B — confirming the diagnosis

How do you confirm the diagnosis, and how reliable is the contrast enema? [5]

The gold standard is a suction rectal biopsy, sampling mucosa and submucosa 1 to 3 cm above the dentate line. Histology shows absent submucosal ganglion cells with hypertrophied nerve trunks. Modern practice uses calretinin immunohistochemistry, which is absent in aganglionic bowel, as a faster and more reliable alternative to acetylcholinesterase staining. Sensitivity approaches 100 per cent with adequate samples. [5] [6]

A contrast enema may show a transition zone between a narrowed distal segment and a dilated proximal colon, but it is only approximately 70 per cent accurate. A normal contrast enema does not exclude Hirschsprung disease. The biopsy always overrides the imaging. [10]

Branch C — the operation

The biopsy confirms short-segment Hirschsprung disease. What operation is done and what are the key principles? [9]

The principle is to remove or bypass the aganglionic bowel and bring ganglionic bowel to the anal canal. The three classical operations are the Swenson (complete resection with end-to-end anastomosis), the Soave (endorectal pull-through through a retained muscular cuff) and the Duhamel (retrorectal pull-through creating a side-to-side neorectum). At operation, frozen-section levelling biopsies confirm the presence of ganglion cells at the anastomotic level. For uncomplicated short-segment disease, a primary transanal Soave pull-through in the neonatal period is now the preferred approach, avoiding a stoma and a second operation. [9] [1]

Branch D — the child with enterocolitis

Now a different scenario: an infant with known Hirschsprung disease awaiting surgery presents with fever, explosive foul-smelling diarrhoea and abdominal distension. What is happening and what do you do? [2]

This is Hirschsprung-associated enterocolitis until proven otherwise. It is the leading cause of death, driven by stasis and bacterial overgrowth behind the obstructed bowel. I would resuscitate aggressively with isotonic intravenous fluid boluses, start broad-spectrum antibiotics including metronidazole for anaerobic cover and an aminoglycoside for Gram-negative cover, decompress with a nasogastric tube and frequent rectal washouts, and involve the surgeon and intensive care immediately. This presentation may shift the surgical plan from a primary pull-through to a staged approach with an initial stoma. [2]

Closing — the safety rule

Give me the single rule you want every junior to hold about Hirschsprung disease. [1]

A term neonate who has not passed meconium within 48 hours has Hirschsprung disease until proven otherwise, confirmed by a suction rectal biopsy. And any child with known or suspected Hirschsprung disease who develops fever, distension and explosive diarrhoea has enterocolitis until proven otherwise, and needs aggressive resuscitation, antibiotics and decompression immediately. [1] [2]