What are the diagnostic tests for Hirschsprung's disease?

Diagnostic Tests for Hirschsprung's Disease

Rectal suction biopsy (RSB) is the gold standard diagnostic test for Hirschsprung's disease, with specimens taken at 1 cm, 3 cm, and 5 cm above the dentate line to demonstrate the absence of ganglion cells in the affected bowel. 1

Primary Diagnostic Approach

Rectal Biopsy

• Rectal suction biopsy (RSB):

  • First-line diagnostic test for infants and children under 6 months of age 2, 3
  • Specimens should be taken at three levels: 1 cm, 3 cm, and 5 cm above the dentate line 1
  • Specimens taken at the dentate line are often not useful (31.5% show squamous or transitional epithelia) 1
  • Adequacy rates: 73.9% at 1 cm, 75.9% at 3 cm, and 79.2% at 5 cm above dentate line 1

• Incisional rectal biopsy:

  • Preferred method for patients older than 6 months 2
  • Significantly lower inadequacy rates compared to suction biopsies in older patients (0.9% vs 24.1%, p<0.01) 2

Histopathologic Evaluation

• Pathologic confirmation requires:
  • Absence of ganglion cells in submucosal and myenteric plexuses
  • Hypertrophied nerve trunks
  • Increased acetylcholinesterase activity in the lamina propria and muscularis mucosae 4

Additional Diagnostic Tests

Anorectal Manometry

• Useful in neonatal period when RSB may be technically challenging
• Weekly rectal manometry can be performed until the end of neonatal period when RSB is done for confirmation 5
• Absence of rectoanal inhibitory reflex indicates Hirschsprung's disease
• Sensitivity of 99% with false-negative rate of 0.9% 5
• Sedation improves results and reduces non-useful studies (2.97% vs 8% without sedation) 5

Contrast Enema

• Supportive diagnostic test showing a transition zone
• Demonstrates narrowed aganglionic segment with proximal colonic dilation
• Most useful in cases with rectosigmoid disease
• May be less reliable in neonates and in total colonic aganglionosis

Diagnostic Algorithm

1. Initial presentation: Delayed passage of meconium beyond 48 hours after birth, abdominal distention, vomiting
2. First diagnostic test:
   • For infants <6 months: Rectal suction biopsy (3 specimens at 1,3, and 5 cm above dentate line)
   • For patients >6 months: Incisional rectal biopsy
3. If RSB is technically challenging in neonates: Perform rectal manometry weekly until RSB can be performed at the end of neonatal period
4. Supportive imaging: Contrast enema to identify transition zone

Complications and Considerations

• RSB complications include:

  • Rectal bleeding (0.5% in patients <1 year) 3
  • Inadequate specimens (14.5%) 3
  • Higher risk of complications in patients <1 year 3

• Incisional biopsy complications:

  • Lower inadequacy rates in patients >6 months 2
  • Requires general anesthesia

Pitfalls to Avoid

• Inadequate depth of biopsy specimen (must include submucosa)
• Improper specimen handling affecting histologic interpretation
• Misinterpretation of immature ganglion cells in neonates
• Relying solely on contrast enema without histologic confirmation
• Taking specimens at the dentate line (often not diagnostic)
• Using suction biopsy in older children when incisional biopsy would be more appropriate

Proper execution of rectal biopsy with expert pathologic evaluation remains the cornerstone of Hirschsprung's disease diagnosis, with the diagnostic approach tailored based on patient age and technical considerations.