Congenital Aganglionic Megacolon (Hirschsprung Disease)

By usmlevideoss

Introduction

Congenital aganglionic megacolon, or Hirschsprung disease (HD), is a congenital disorder characterized by the absence of ganglion cells in the distal bowel due to neural crest cell migration failure during fetal development. This results in a lack of coordinated peristalsis and functional obstruction.

Pathophysiology

  1. Neural Crest Cell Migration Failure:
    • Ganglion cells in the submucosal (Meissner’s) and myenteric (Auerbach’s) plexuses fail to develop in the affected bowel segment.
  2. Aganglionic Segment:
    • Most commonly involves the rectosigmoid region (80% of cases).
    • Can extend proximally in severe cases.
  3. Functional Obstruction:
    • The aganglionic segment remains tonically contracted, causing proximal bowel dilation and distension.

Epidemiology

  • Incidence: 1 in 5,000 live births.
  • Male-to-female ratio: 4:1.
  • Associated with Down syndrome and other genetic syndromes.

Clinical Features

  1. Neonates:
    • Failure to pass meconium within the first 24 hours of life (classic sign).
    • Abdominal distension.
    • Bilious vomiting or feeding intolerance.
  2. Infants/Children:
    • Chronic constipation or infrequent bowel movements.
    • Foul-smelling, ribbon-like stools.
    • Failure to thrive with poor weight gain and hypoproteinemia.
  3. Complications:
    • Enterocolitis: Life-threatening complication with fever, explosive diarrhea, and sepsis.
    • Bowel perforation and peritonitis in severe cases.

Diagnosis

  1. Clinical Assessment:
    • History of delayed meconium passage, chronic constipation, or abdominal distension.
    • Digital rectal examination:
      • Anal canal and rectum devoid of fecal material despite retained stool on imaging.
      • Squirt sign: Gush of flatus and stool as the finger is withdrawn if the aganglionic segment is short.
  2. Imaging Studies:
    • Abdominal X-ray: Shows distended bowel loops with a transition zone.
    • Contrast enema: Identifies the transition zone between the dilated normal bowel and the contracted aganglionic segment.
  3. Definitive Diagnosis:
    • Rectal Biopsy:
      • Absence of ganglion cells in the submucosal and myenteric plexuses.
      • Nerve trunk hypertrophy and increased acetylcholinesterase activity on special staining.
  4. Anorectal Manometry (Optional):
    • Failure of the internal anal sphincter to relax.

Management

  1. Definitive Treatment:
    • Surgical resection of the aganglionic segment (e.g., Swenson, Soave, or Duhamel procedures).
    • Pull-through procedure to connect normal innervated bowel to the anus.
  2. Preoperative Care:
    • Manage obstruction with rectal irrigation and bowel decompression.
    • Treat enterocolitis if present with IV fluids and antibiotics.
  3. Postoperative Care:
    • Monitor for complications such as:
      • Anastomotic strictures.
      • Leakage.
      • Recurrent enterocolitis.

Prognosis

  • Most children achieve good bowel function after surgery.
  • Long-term issues may include:
    • Constipation.
    • Soiling.
    • Recurrent enterocolitis in some cases.

SUPERPoint: Hirschsprung disease results from aganglionic segments in the colon, typically presenting with failure to pass meconium, and is definitively treated with surgical resection.

SUPERFormula: Days old baby is brought by parents because he failed to pass meconium, has abdominal distention and bilious vomiting + caused by failure of neural crest cell migration, leading to absent ganglion cells in the distal bowel + most commonly affects the rectosigmoid region + diagnosis confirmed by rectal biopsy showing absent ganglion cells and hypertrophied nerve fibers + managed with surgical resection of the aganglionic segment and pull-through procedures = Congenital Aganglionic Megacolon (Hirschsprung Disease).