Key Facts

Hirschsprung disease is a congenital motility disorder caused by failure of neural crest cell migration to the distal bowel during embryonic development, resulting in an aganglionic segment that fails to relax. It is the most common cause of lower intestinal obstruction in neonates.

Epidemiology

Incidence is approximately 1 in 5,000 live births. Male predominance is 4:1 for short-segment disease but approximately 2:1 for long-segment. Associated with Down syndrome in 5-10% of cases. Familial cases occur in ~5% (higher in long-segment disease — up to 20%). Other syndromic associations include MEN2A/2B, Waardenburg syndrome, and Smith-Lemli-Opitz syndrome.

Aetiology

Hirschsprung disease results from failure of neural crest cell (enteric ganglion cell precursor) migration from the vagal neural crest to the distal bowel during weeks 5-12 of gestation. Migration proceeds craniocaudally, which is why the rectum is always affected.

Genetic factors: RET proto-oncogene mutations are the most common identifiable cause (~50% of familial, ~20% of sporadic cases). Mutations in EDNRB, EDN3, SOX10, and GDNF are also implicated.

Pathophysiology

Absent ganglion cells in the myenteric (Auerbach's) and submucosal (Meissner's) plexuses → failure of inhibitory relaxation of the aganglionic segment → functional obstruction. The proximal normally innervated bowel dilates (megacolon) as it tries to propel contents past the non-relaxing segment. The internal anal sphincter fails to relax (absent rectoanal inhibitory reflex). Stasis of bowel contents predisposes to Hirschsprung-associated enterocolitis (HAEC).

Neonatal Presentation (80%)

• Failure to pass meconium within 48 hours of birth (most common presenting feature)
• Abdominal distension
• Bilious vomiting
• Reluctance to feed
• 'Explosive' passage of stool and gas after digital rectal examination ('blast sign')

Late/Older Child Presentation

• Chronic constipation refractory to medical management
• Abdominal distension
• Failure to thrive, poor weight gain
• Ribbon-like stools
• Recurrent faecal impaction

Hirschsprung-Associated Enterocolitis (HAEC)

• Fever, abdominal distension, explosive foul-smelling diarrhoea
• Lethargy, poor feeding
• May progress rapidly to sepsis, perforation, and death
• Can occur pre- or post-operatively (most common complication)

Red Flags

• Failure to pass meconium >48 hours — investigate for Hirschsprung disease
• Enterocolitis symptoms in known/suspected Hirschsprung — emergency management
• Chronic constipation from birth with empty rectum on examination (rectum is usually full in functional constipation)
• Abdominal distension out of proportion to constipation

Bedside

• Abdominal examination: Distension, palpable faecal masses
• Digital rectal examination: Empty rectum with explosive release of stool/gas on withdrawal of finger ('blast sign')
• Passage of meconium: Document timing

Bloods

• FBC, CRP: If enterocolitis suspected
• U&Es: Electrolyte imbalance from vomiting/third-space losses
• Blood gas: Metabolic acidosis if sepsis/perforation
• Blood cultures: If HAEC suspected

Imaging

• Abdominal X-ray: Dilated loops of bowel, absence of rectal gas
• Contrast enema (unprepared): Shows transition zone (calibre change between narrow aganglionic distal segment and dilated proximal segment); 24-hour delayed film may show retained contrast (abnormal in Hirschsprung)

Special Tests

• Suction rectal biopsy: Gold standard — absence of ganglion cells in submucosal plexus with hypertrophied nerve fibres and positive acetylcholinesterase staining; calretinin immunohistochemistry (absent in Hirschsprung)
• Anorectal manometry: Absent rectoanal inhibitory reflex (RAIR) — useful screening test but not diagnostic alone
• Full-thickness biopsy: If suction biopsy is equivocal — performed under GA

Non-pharmacological

• Rectal washouts: Regular saline washouts (10-20ml/kg warm saline) to decompress the bowel — bridge to surgery
• Nutritional support: Optimise nutrition prior to surgery

Pharmacological

• HAEC treatment: IV broad-spectrum antibiotics (e.g., metronidazole 7.5mg/kg TDS + gentamicin 7mg/kg OD or ceftriaxone 80mg/kg OD), IV fluids, rectal washouts, NG decompression
• Prophylactic rectal washouts ± metronidazole: May reduce HAEC risk post-operatively

Surgical/Interventional

• Temporary stoma (levelling colostomy): Formed in normally ganglionated bowel if child is very unwell, premature, or enterocolitis is severe; allows recovery before definitive pull-through
• Pull-through procedure (definitive): Resection of aganglionic segment with anastomosis of normally innervated bowel to the anal canal
  • Soave (endorectal): Mucosectomy of aganglionic rectum, pull-through within rectal muscular cuff — most commonly used
  • Duhamel: Ganglionic bowel brought behind aganglionic rectum
  • Swenson: Full-thickness resection of aganglionic segment, end-to-end anastomosis
  • Can be performed as single-stage procedure (increasingly common) or after initial stoma
  • Laparoscopic-assisted approaches are standard at most centres

Referral Criteria

• All suspected Hirschsprung disease — urgent paediatric surgical referral
• HAEC — emergency surgical admission
• Chronic constipation from infancy not responding to treatment — consider Hirschsprung

• Post pull-through outcomes: >90% achieve satisfactory bowel function
• Soiling/incontinence: Occurs in 10-20% of patients in early years; improves with age
• Constipation post-surgery: 10-15% have ongoing constipation requiring management
• HAEC: Occurs in ~20-30% of patients (pre- or post-operatively); mortality up to 30% if untreated but <1% with prompt treatment
• Enterocolitis risk: Persists for several years post-surgery; parents must be educated to recognise symptoms
• Long-segment disease and total colonic aganglionosis: Poorer functional outcomes; may require longer-term nutritional support
• Overall survival: >95% with appropriate surgical management

Classification by Extent

Distinguishing Hirschsprung from Functional Constipation