A focal pulmonary F-18 FDG uptake without pulmonary CT abnormality in PET/CT probably due to mislocation of the urine F-18 FDG in the left upper renal calyx.

We experienced a case of a focal pulmonary F-18 fluoro-2-deoxy-D-glucose (FDG) uptake without pulmonary computed tomography (CT) abnormality probably due to the urine FDG in the upper pole calyx of the left kidney. A 76-year-old male patient was referred for evaluation of the postoperative right lung cancer. Positron emission tomography/CT was performed 1 hour after intravenous injection of FDG and showed a small focus of increased uptake in the left lower lung field accompanying no abnormality in the corresponding lung CT images. The lung uptake was not noted in repeated positron emission tomography/CT images taken after 1 hour, suggesting misplacement of the left renal upper calyx into the lower lung.