Biliary ascariasis is a complication of intestinal ascariasis. This results in characteristic findings in the intravenous cholangiocholecystogram and in the sonogram. Characteristic signs of biliary ascariasis are, in the longitudinal section, the "strip sign", "spaghetti sign", "inner tube sign", and in transverse section "a bull's eye in the triple O". The helminth can travel from out of the biliary duct system back into the intestines, so that control examinations can even be negative.