This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
In case of new born the commonest cause of intestinal obstruction is - 
Select and explain. 
A. Annular pancreas, B. Duodenal Atresia, C. Jejunal atresia, D. Oesophageal atresia
B: Duodenal Atresia
Answer: B: Duodenal Atresia 
Explanation: Congenital atresia and stenosis are the commonest cause.
The incidence of atresia varies with anatomical site:
duodenum - 35percent
jejunum - 15percent
ileum - 25percent 
ascending colon - 10percent
multiple sites  - 15percent


Vomiting is bile stained or not, depends on the atresia proximal or distal to ampulla of vater. In 85% of cases the atresia is distal to the ampulla, therefore the vomiting is bilious.
Approximately 1/3 of newborns with duodenal atresia have associated Down's syndrome.
The 'double bubble seen on the air contrast upper GI series is characteristic of duodenal atresia.
Treatment of choice is - Duodenoduodenostomy