Posterior Bladder Layering Sign on FDG PET/CT: A Report of Two Cases

Posterior bladder layering sign of excreted F-18 FDG is rarely seen on positron emission tomography/computed tomography (PET/CT). It is determined to be present when there is a well-defi.ned settlement of radioactivity toward to the bottom of the urinary bladder during whole-body scanning. We presented two cases with posterior bladder layering sign of excreted F-18 FDG on PET/CT imaging. A 47-year-old male with oropharyngeal cancer underwent F-18 FDG PET/CT scan for evaluation and following treatment planning. He finished concurrent chemoradiotherapy one month ago. PET/CT scan showed mild to moderate FDG uptake in right middle lobe, left lower lobe and right lower lobe in the bilateral lungs. These findings were showed infections in the bilateral lungs. Besides, the patient presented with high CRP level of 11.2 mg/dL. The urinary bladder with well-demarcated F-18 FDG-Ioaded urine in the bottom and clear urine at the top was accidentally noted. Another 76-year-old male with tonsilar cancer underwent F-18 FDG PET/CT for further evaluation. A distended urinary bladder with a clear discrimination between the urine without F-18 FDG radioactivity was showed on the top of bladder. F-18 FDG-Ioaded urine in the bottom was also incidentally noted.