<prompt> In gallstone ileus, obstruction is seen atJejunumProximal ileumDistal ileumColon  <response>: Gallstone ileus Passge of stone through a spontaneous biliary-enteric fistula leading to a mechanical bowel obstruction Most common site of fistula : Between the gallbladder and duodenum Clinical features Riglers triad - Classic pain abdominal film triad of small bowel obstruction, pneunobilia ectopic gallstone is considered pathognomic Most common site of obstruction is ileum60; jejunum 15; colon5 sigmoid colon duodenum 5 Ref:1506-1507 