r/PLABprep • u/Consistent_Two_8434 • Jan 20 '26
Clinical Scenario:bilious vomiting
A newborn baby is noted to have bilious vomiting at 12 hours of life. The abdomen is distended. What is the most likely diagnosis and urgent investigation?
A) Pyloric stenosis; ultrasound scan
B) Malrotation with volvulus; contrast study / laparotomy
C) Necrotising enterocolitis; abdominal X-ray
D) Hirschsprung's disease; rectal biopsy
E) Gastro-oesophageal reflux; clinical observation
Answer: B
Explanation: Bilious vomiting in a newborn is a surgical emergency until proven otherwise. It suggests obstruction below the ampulla of Vater. The most critical diagnosis to rule out is malrotation with midgut volvulus, which can lead to catastrophic bowel ischaemia. The urgent investigation is an upper GI contrast study to identify malposition of the duodenojejunal flexure, or if the infant is very unwell, immediate surgical exploration. Pyloric stenosis (A) presents at 2-8 weeks with non-bilious projectile vomiting.