Spectral computed tomography as a method for identifying radiolucent gallstones.

We present the case of an 82-year-old woman with history of right colon adenocarcinoma in whom a routine control scan is performed using a dual-layer detector spectral CT scanner. Conventional CT scan images show a dilated cystic bile duct with no apparent cause of obstruction, finding also no lithiasis inside the gallbladder. Non-calcified gallstones are composed mainly of cholesterol and can have the same radiographic density as bile, making them hard or impossible to spot on conventional CT.