<prompt> Bent inner tube sign is seen inVolvulusIntussusceptionIntestinal obstructionGastric antral vascular ectasia  <response>: Ans. a VolvulusRef: Manipal Manual of surgery, 4th ed.739 In sigmoid volvulus, the X ray abdomen erect shows hugely dilated sigmoid loop called bent inner tube sign. Acute sigmoid volvulus presents as intestinal obstruction and starts after straining at stool. It occurs in anti-clockwise direction and after one and a half turns, the entire loop becomes gangrenous. The percussion note on the abdomen shall be tympanitic note. 