Calyceal Diverticulum Found Incidentally on 18 F-FDG PET/CT Imaging.

A 69-year-old man with pancreatic cancer underwent 18 F-FDG PET/CT examination for tumor staging. The PET images showed a focal mass-like FDG accumulation in the left kidney mimicking malignancy, whereas simultaneous CT and fused PET/CT images suggested a cystic lesion. On subsequent MR examination, the lesion appeared cystic on T2-weighted, contrast-enhanced arterial phase, and contrast-enhanced venous phase images. In addition, excretory phase images showed filling contrast medium to the cystic cavity, leading to a diagnosis of calyceal diverticulum. This report suggests that the possibility of a calyceal diverticulum should be considered in cases with focal FDG accumulation in renal cystic lesions.