Overview

Hirschsprung Disease (Congenital Megacolon) is a developmental disorder characterized by the absence of ganglion cells (aganglionosis) in the distal bowel. It is the most common cause of neonatal lower intestinal obstruction, occurring in approximately 1 in 5,000 live births, with a strong male predominance (4:1).

It is caused by premature arrest of craniocaudal migration of vagal neural crest cells. The aganglionic segment starts at the internal anal sphincter and extends proximally for a variable distance.

Embryology

During embryogenesis, enteric ganglion cell precursors (derived from neural crest cells) migrate craniocaudally along the vagal trunk to populate the gastrointestinal tract. This migration occurs between weeks 5 and 12 of gestation.

• Week 5: Precursors reach the esophagus.
• Week 7: Precursors reach the midgut.
• Week 12: Migration is completed to the rectum.

In Hirschsprung Disease, migration is prematurely arrested, resulting in a distal aganglionic segment. The earlier the migration stops, the longer the aganglionic segment.

Anatomy

The aganglionic segment affects both the Meissner (submucosal) and Auerbach (myenteric) plexuses. The absence of these cells leads to continuous tonic contraction of the affected segment, creating a functional obstruction.

• Short-segment disease (80%): Aganglionosis is restricted to the rectosigmoid region.
• Long-segment disease (15%): Aganglionosis extends proximal to the colon.
• Total colonic aganglionosis (5%): Aganglionosis involves the entire colon and occasionally terminal ileum.

Clinical Features

The classic presentation is a newborn presenting with acute lower intestinal obstruction. Key diagnostic findings include:

1. Delayed passage of meconium: Failure to pass meconium within the first 24–48 hours of life.
2. Abdominal Distension: Progressive abdominal bloating.
3. Bilious Vomiting: Indicates low intestinal obstruction.
4. Squirt Sign: Explosive release of gas and stool on digital rectal exam.

Diagnosis

• Rectal Suction Biopsy: Shows absence of ganglion cells in submucosa and hypertrophied nerve fibers showing acetylcholinesterase (AChE) activity.
• Anorectal Manometry: Demonstrates absence of Rectoanal Inhibitory Reflex (RAIR).
• Contrast Enema: Shows narrow distal segment and dilated proximal segment.

Management

Resuscitation and colonic decompression using warm saline rectal irrigations. Definitive surgeries include Swenson, Duhamel, or Soave pull-through procedures.

Complications

Hirschsprung-Associated Enterocolitis (HAEC) is the most common cause of mortality. Anastomotic stricture, bowel leak, fecal incontinence, and chronic constipation.

FCPS/MS High-Yield Points

Associated with RET proto-oncogene mutations, EDNRB (endothelin receptor B), and Trisomy 21 (Down syndrome). Biopsies must be taken at least 2 cm above the dentate line.

Viva Questions

Q1: Why is transition zone not seen in early neonates? A: Requires weeks of peristaltic work to dilate proximal colon.

MCQs

Q1: Stain helpful in aganglionosis? A: Acetylcholinesterase (AChE) stain.

Lecture Videos

Watch pull-through guides in our Video Library.

PDFs

Download our clinical handbooks from the Downloads repository.

Guidelines

Elective pull-through performed at 2-3 months of age in stable infants.

References

1. Coran’s Pediatric Surgery, 7th Edition.
2. Ashcraft’s Pediatric Surgery, 7th Edition.