A grossly dilated, twisted colonic loop on plain film (the coffee-bean / bent inner tube sign, also called the inverted omega or inverted-U loop) means sigmoid volvulus, which accounts for >90% of colonic volvulus. Caecal volvulus looks different: a kidney-shaped or comma-shaped gas shadow in the left upper quadrant. Transverse and ascending colon volvulus are rare and have no classic sign.