Bilious vomiting and intestinal obstruction — branching viva

Opening — framing the problem

The examiner begins: a 4-day-old term baby, previously feeding well, suddenly vomits bright green fluid and looks comfortable with a soft abdomen. What is your first thought? ^[1]

My first thought is that this is malrotation with midgut volvulus until proven otherwise, because green vomit means the obstruction is beyond the ampulla and a volvulus can strangle the whole midgut within hours. I am not reassured by the soft abdomen, because tenderness, distension and shock are late signs, so I would treat this as a surgical emergency from the outset. ^{[1] [2]}