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: Radiology
Coffee bean sign is a radiologic finding in which of the following abdominal condition? 
Select and explain. 
A. Ileocaecal TB, B. Sigmoid volvulus, C. Ulcerative colitis, D. Crohn's disease
B: Sigmoid volvulus
Answer: B: Sigmoid volvulus 
Explanation: Volvulus refers to torsion of the bowel. It most commonly occurs in the sigmoid colon or caecum of constipated elderly adults who have redundant loops of colon on a long mesentery and are therefore at risk of the colon twisting around its mesenteric axis. Coffee bean sign is a radiologic feature of sigmoid volvulus which occur when two grossly distended loops of bowel are closely apposed their compressed medial walls forms a central cleft resembling o coffee bean. Other abdominal X ray features of volvulus are: Grossly distended inveed U shaped loop of sigmoid colon extending from the pelvis to the diaphragm with a curved inner colonic wall. RUQ pointing loop suggests sigmoid volvulus and LUQ pointing loop suggests cecal volvulus. Loss of haustral folds due to distention. Ref: Radiology at a Glance By Rajat Chowdhury, page 43.