Uncommon cause of percutaneous fistulation

We report the case of a woman in her mid-60s with a 9 month history of a lesion to the right posterolateral flank presenting as a gradually enlarging, inflamed pink papule, which developed into a fistulating sinus tract discharging onto the skin. Radiological investigation identified a 'dropped' gallstone as the cause of this. 'Dropped' or retained gallstones are a common complication in laparoscopic cholecystectomy, but only rarely cause clinical complications. We flag this case as an interesting differential diagnosis for unexplained abdomino-percutaneous fistulation in patients who have previously undergone cholecystectomy.