Situation: A nurse on the pediatric surgical ward cares for infants with congenital anomalies of the bowel and nervous system. A term newborn has not passed meconium in the 48 hours since birth. His abdomen is distended, and he has vomited green fluid. On digital rectal examination the rectum is tight and empty, and an explosive release of gas and stool follows. Which condition do these findings MOST suggest?

Failure to pass meconium in the first 24–48 hours, abdominal distension, bilious vomiting, and a tight, empty rectum with an explosive release of stool on examination are the classic newborn signs of Hirschsprung disease, caused by absent ganglion cells in the distal bowel. A rectal suction biopsy confirms it.

Core clinical reasoning
The combination of failure to pass meconium within 48 hours, abdominal distension, bilious vomiting, and a tight, empty rectum that suddenly releases gas and stool during digital rectal examination is the classic newborn presentation of Hirschsprung disease. The underlying problem is congenital absence of ganglion cells in the distal bowel, which leaves that segment tonically contracted and functionally obstructed ^[4]. Stool accumulates above the aganglionic zone, so the rectum itself remains narrow and empty until the examiner’s finger mechanically opens the spastic segment and triggers the explosive evacuation.

Why the other options do not fit
Hypertrophic pyloric stenosis causes non-bilious, projectile vomiting in the first weeks of life, but it does not produce abdominal distension, delayed meconium passage, or rectal findings. Meconium ileus from cystic fibrosis also presents with failure to pass meconium and bilious vomiting, but the obstruction is caused by inspissated meconium in the terminal ileum; the rectum is typically small and empty without the explosive release seen here. Imperforate anus with a perineal fistula is identified on inspection—there is no normal anal opening, and meconium may pass through a visible fistula tract, which is not described in this scenario.

Diagnostic confirmation
The definitive test is a rectal suction biopsy demonstrating absence of ganglion cells ^[2][3]. Contrast enema and anorectal manometry may be used as screening tools, but histopathological evaluation of a rectal biopsy remains the gold standard ^[2]. The biopsy should be taken from the narrow, aganglionic distal segment; sampling too low in the anal canal can produce a false-negative result because a short physiologic aganglionic zone exists normally.

Clinical course and timing
Most affected infants present in the first days after birth with signs of bowel obstruction ^[4]. Early diagnosis—before 1 year of age—is associated with a more favorable perioperative course and better long-term functional outcomes than late diagnosis . In this newborn, the 48-hour history of no meconium already exceeds the expected 24–48 hour window for first stool passage, making prompt evaluation essential.

Feature	Hirschsprung disease	Meconium ileus	Pyloric stenosis
Age at onset	Newborn period	Newborn period	2–6 weeks
Vomiting	Bilious	Bilious	Non-bilious, projectile
Abdomen	Distended	Distended	Usually flat, visible peristalsis
Rectal exam	Tight, empty; explosive stool release	Empty; no explosive release	Normal
Definitive test	Rectal suction biopsy	Sweat chloride, genetic testing	Ultrasound of pylorus

Key point! The explosive release of stool after digital rectal examination is a hallmark finding that points specifically to Hirschsprung disease rather than other causes of neonatal bowel obstruction. Watch out! A normal contrast enema does not exclude Hirschsprung disease; only a rectal biopsy showing aganglionosis confirms the diagnosis ^[2][3].