Congenital Colonic Stenosis in a Preterm Infant: A Diagnostic Trap and the Potential Masking Effect of a Liquid Diet.

Background: Congenital colonic stenosis (CCS) is a rare cause of neonatal bowel obstruction due to a focal luminal narrowing. We report a premature infant in whom a high-grade CCS remained clinically compensated for months during exclusively liquid feeding. Case Presentation: An 8-month-old corrected-age female infant (born at 28+5 weeks' gestation; body weight (BW): 1095 g) presented to the Emergency Department with acute abdominal distension, bilious emesis, and obstipation, despite a history of steady weight gain and chronic mild abdominal distension. A neonatal contrast enema had previously shown an abrupt cutoff suggestive of obstruction, but this was attributed to a procedural artifact given her tolerance of feeds and passage of loose stools; a rectal suction biopsy excluded Hirschsprung disease. Within four days of introducing complementary solid foods at 8 months corrected age, her compensation failed and complete functional obstruction developed. A repeat contrast enema confirmed a short-segment, annular stenosis of the distal descending colon. Conservative management with a liquid diet failed, and definitive surgical resection with primary anastomosis was performed approximately one month later, achieving immediate symptom resolution and long-term catch-up growth. Conclusions: Reassuring weight gain and liquid stool passage can create a diagnostic trap, masking a high-grade colonic structural obstruction. Clinicians must not disregard reproducible focal anomalies on neonatal contrast imaging based solely on clinical plausibility.