This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Small & Large Intestine, Subject name: Surgery
Etiology for this condition: 
Select and explain. 
A. Adhesive obstruction, B. Sigmoid volvulus, C. Meckel's diverticulum, D. Gastric volvulus
B: Sigmoid volvulus
Answer: B: Sigmoid volvulus 
Explanation: Ans. (b) Sigmoid volvulusRef: Bailey and Love 26th edition, Page 1195* Most common site of volvulus in colon -- sigmoid* Most common direction of volvulus is anticlockwise > Clockwise* X-ray shows --Coffee-bean or bent inner tube sign* Barium enema shows -- Bird beak sign