What is the role of a Digital Rectal Examination (DRE) in diagnosing and managing Hirschsprung disease in a newborn or infant patient?

Digital Rectal Examination in Hirschsprung Disease

Digital rectal examination (DRE) plays a limited but specific role in Hirschsprung disease: it should be performed to assess sphincter tone and may trigger an explosive release of stool and gas in affected infants, but it is NOT diagnostic and should never delay definitive rectal biopsy when Hirschsprung disease is suspected. 1, 2

Clinical Utility of DRE in Hirschsprung Disease

What DRE Can Reveal

• Tight anal sphincter tone is commonly found on DRE in infants with Hirschsprung disease, though this finding is neither sensitive nor specific 1
• Explosive passage of stool and gas following digital stimulation or DRE is a classic finding that suggests Hirschsprung disease, occurring because the aganglionic segment prevents normal stool passage until mechanical disruption 3, 2
• An empty rectal vault on DRE despite abdominal distension is suggestive of Hirschsprung disease, as stool accumulates proximal to the aganglionic segment 2

Critical Limitations

DRE cannot diagnose or exclude Hirschsprung disease - the definitive diagnosis requires rectal biopsy demonstrating absence of ganglion cells and positive acetylcholinesterase staining. 2, 4, 5

Key Clinical Features That Should Prompt Evaluation

When evaluating a newborn or infant for possible Hirschsprung disease, focus on these specific historical and examination findings:

History (in order of importance)

• Delayed passage of meconium beyond 48 hours of life - present in 60% of Hirschsprung patients versus only 15% with idiopathic constipation 2
• Bilious vomiting in the newborn period - occurred in 35% of Hirschsprung cases 3
• Abdominal distension - significantly more common in Hirschsprung disease 3, 2
• Onset of symptoms in the first week of life - seen in 60% of Hirschsprung patients 2

Physical Examination Findings

• Perform DRE using the fifth finger (little finger) in newborns to minimize trauma 1
• Assess for tight sphincter tone and empty rectal vault 1, 2
• Observe for explosive stool passage after digital stimulation 2
• Note degree of abdominal distension 3, 2

Diagnostic Algorithm

All patients with Hirschsprung disease have one or more of these features: delayed meconium passage, abdominal distension, vomiting, or transition zone on contrast enema. 2

When to Proceed with Rectal Biopsy

Perform rectal suction biopsy when ANY of the following are present: 2, 5

• Delayed passage of meconium beyond 48 hours
• Abdominal distension with constipation
• Bilious vomiting in a newborn
• Transition zone on contrast enema
• Low intestinal obstruction of unknown cause
• Severe constipation with failure to thrive

When Rectal Biopsy May Be Avoided

In children with constipation who have NONE of the above features, rectal biopsy is not necessary to exclude Hirschsprung disease - this approach can avoid unnecessary biopsies in approximately 36% of patients with idiopathic constipation. 2, 5

Imaging Considerations

• Contrast enema is the diagnostic imaging procedure of choice when distal bowel obstruction is suspected, and can identify a transition zone in 92% of Hirschsprung cases 6, 3
• Contrast enema helps differentiate Hirschsprung disease from other causes of distal obstruction including meconium plug, ileal atresia, and meconium ileus 6

Definitive Diagnosis

• Rectal suction biopsy has 81% sensitivity and 97% specificity for diagnosing Hirschsprung disease 4
• The biopsy must demonstrate absence of ganglion cells in the submucosa and positive acetylcholinesterase staining in the lamina propria and muscularis mucosa 4, 5
• A second biopsy may be needed in 15-22% of cases when the first is equivocal or inadequate 4, 5
• Rectal suction biopsy can be safely performed in preterm infants with similar diagnostic accuracy (83% sensitivity, 97% specificity), so there is no reason to delay biopsy in premature infants 4

Critical Pitfalls to Avoid

• Never rely on DRE alone to exclude Hirschsprung disease - proceed with rectal biopsy when clinical suspicion exists 2, 4
• Do not delay biopsy in preterm infants - it can be performed safely and accurately once they are clinically stable 4
• Be aware that 8% of suction biopsies may be inadequate for diagnosis, requiring repeat biopsy 5
• Remember that approximately 35% of Hirschsprung patients have associated congenital anomalies, including Down syndrome and cardiac defects 3