A Endoscopy.

[Feedback :- This baby may have a malrotation, and an urgent upper GI contrast study is required to exclude the diagnosis.]

B Upper GI contrast study.

This is the Correct Answer

[Feedback :- The most important cause of bile-stained vomiting that needs to be excluded is a malrotation with volvulus. Clinical examination and plain abdominal radiograph are often unremarkable in these cases, and an upper GI contrast study is required to confirm the diagnosis.]

C Lower GI contrast study.

[Feedback :- This baby may have a malrotation, and an urgent upper GI contrast study is required to exclude the diagnosis.]

D Plain abdominal radiograph.

[Feedback :- A plain abdominal radiograph is often unremarkable in these cases, and while one should be performed an upper GI contrast study will still be required urgently.]

E Ultrasound of the abdomen.

[Feedback :- This baby may have a malrotation, and an urgent upper GI contrast study is required to exclude the diagnosis.]