What’s the Gut Doing in the Chest? Interpositio Hepatodiaphragmatica (Chilaiditi Sign) Revisited on 18F-FDG PET/CT

A 47-year-old woman, a diagnosed case of syndrome of inappropriate secretion of antidiuretic hormone, underwent 18 F-FDG PET/CT to detect occult malignancy for suspected paraneoplastic etiology. Abnormal FDG uptake was noted in the right lower chest region, which was correlated on corresponding CT images to be colonic activity interposed between the liver and elevated diaphragm, also known as Chilaiditi sign. Even though rare, Chilaiditi sign should be considered as a differential diagnosis of hypermetabolic activity in the right lower chest region on 18 F-FDG PET/CT scan that is done to look for occult tumor as shown in this case.