Hirschsprung disease (congenital megacolon)

A normal barium enema does not exclude Hirschsprung's disease. Up to 90 per cent of infants with Hirschsprung's disease fail to pass meconium in the first 24 hours of life

About

• Starting distally the myenteric ganglion cells are absent in bowel wall.
• Congenital megacolon Seen in 1 in 5000 live births

Associations

• Family history of Hirschsprung disease
• Neurofibromatosis
• Down syndrome
• VSD, Renal agenesis
• Waardenburg's syndrome
• Multiple endocrine neoplasia, type IIA

Pathology

• Failure of neural crest cell migration to the distal large intestine
• Absence of ganglion cells in Auerbach's plexus (parasympathetic)
• Failure of relaxation and functional obstruction
• Proximal bowel becomes progressively dilated

Aetiology

• 70% involves rectosigmoid and 20% the colon too
• In 10% the small intestine can be involved
• Aganglionic bowel cannot do peristalsis
• It therefore passively constricts with mechanical obstruction.

Clinical

• Initially well and then fails to pass meconium
• Abdominal distension, bloating, vomiting, and poor feeding
• Milder cases with constipation
• Hirschsprung's enterocolitis can occur with distension and diarrhoea

Differentials

Investigations

• Rectoanal manometry (balloon distention of the rectum) demonstrates the absence of internal anal sphincter relaxation upon rectal distention.
• Contrast enema and anal manometry are similar in sensitivity and specificity
• Rectal biopsy shows the absence of ganglion cells and the presence of hypertrophic nerve trunks. Note that the biopsy site should at least be 0.6 in (1.5 cm) above the dentate line because the distal rectum normally does not have ganglion cells

Management

• If enterocolitis or unwell then colostomy in normal bowel and surgery planned.
• Before surgery, serial rectal irrigation helps decompress the bowel and prevent enterocolitis.
• Swenson's involves removing the rectum, pulling the healthy ganglionated colon through, and connecting it through to the anus
• Bowel control is likely to be imperfect for a number of years

References

• Hirschsprung's Disease: Diagnosis and Management