A 63-year-old woman presented with a recent complaint of painless hematuria. Cystoscopy showed no evidence of a bladder tumor. Renal ultrasound was negative. FDG PET/CT was performed under the suspicion of occult malignancy. The initial routine PET images seemed unremarkable, whereas the coregistered CT images revealed a soft tissue density lesion in the upper pelvis of the left kidney. On the delayed PET/CT scan of the kidneys after intravenous administration of furosemide and oral hydration, focal intense FDG uptake in the left upper renal pelvis was revealed. Thereafter, ureteroscopic biopsy of the left renal pelvic lesion was done and pathology confirmed high-grade urothelial cell carcinoma. This case demonstrated the usefulness of the delayed diuretic imaging technique for improving the visualization of tumor uptake in the renal collecting system by decreasing the urinary artifact. It is a simple, noninvasive, and easily performed method to facilitate detection of urinary tract tumors, especially when abnormal CT findings exist.
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