This plain xray shows gas in the biliary tree which is dilated. This most commonly occurs in patients who have had surgery to the common bile duct or gall bladder such as cholecyst enterostomy, choledocho duodenostomy, ERCP and sphincterotomy, or hepatico jejunostomy. It may also be seen in gall stone ileus where a gall stone has eroded from the gall bladder into the duodenum and, very rarely, due to gas forming organisms in the biliary tree.