Gallstone ileus with an enterovaginal fistula: a rare complication of pelvic radiotherapy.

Gallstone ileus is a rare cause of small bowel obstruction. Chronic gallstone irritation can lead to the formation of a cholecystoduodenal fistula, with gallstone impaction typically in the terminal ileum. Rarely gallstones can become impacted in other structures such as the colon or can even erode through the bowel.