Recallab › Question bank › Paediatrics › Respiratory › #50192
Meconium ileus
A term newborn has not passed meconium by 48 hours and has bilious vomiting with abdominal distension. Contrast enema shows a small-calibre colon with inspissated pellets in the terminal ileum. Which underlying condition should be sought?
- correctA. Cystic fibrosis
- B. Duodenal atresia
- C. Hirschsprung disease
- D. Congenital hypothyroidism
Explanation
Key fact
Meconium ileus is cystic fibrosis until proved otherwise - and it is often the first presentation, before any chest disease.
Cystic fibrosis. Thick dehydrated meconium obstructing the terminal ileum, with an unused microcolon, is the classic neonatal presentation.
How it happens
- Failure to pass meconium in 48 hours with bilious vomiting is distal obstruction.
- Contrast shows a microcolon - a colon that has never been used.
- That places the obstruction in the terminal ileum, not the colon.
- Pancreatic enzyme deficiency and abnormal intestinal secretions make the meconium thick and sticky.
- It impacts in the terminal ileum and cannot be passed.
- Around 15% of infants with cystic fibrosis present this way.
An unused colon is the clue, and it points upstream
Why not the others
- B. Duodenal atresia — causes bilious vomiting in the first hours with a double-bubble on plain film and no distal gas. Meconium is often passed.
- C. Hirschsprung disease — also presents with delayed meconium, but contrast enema shows a transition zone with a narrow aganglionic distal segment and dilated proximal bowel, not a microcolon with ileal pellets.
- D. Congenital hypothyroidism — can delay meconium passage but does not cause mechanical obstruction with a microcolon.
Remember
Microcolon plus ileal pellets equals meconium ileus equals cystic fibrosis. Send the sweat test and the genetics.
Go deeper
Uncomplicated cases may be relieved by a hyperosmolar gastrografin enema, which draws fluid in and loosens the plug; complicated cases with volvulus, atresia or perforation need surgery.
Do not confuse it with the meconium plug syndrome, a benign functional colonic obstruction, or with distal intestinal obstruction syndrome, the equivalent problem in older children with cystic fibrosis.
Long-term care needs pancreatic enzyme replacement with every meal and supplements of the fat-soluble vitamins A, D, E and K.
Ghai Essential Pediatrics, 10th ed. (CBS Publishers, 2025); Nelson Textbook of Pediatrics, 22nd ed. (Elsevier, 2024).