An 86-year-old woman with acute renal failure and bilateral hydronephrosis was referred for placement of bilateral percutaneous nephrostomy tubes. She had been diagnosed with urinary obstruction and chronic bacterial urinary tract infections based on the results of urine culture and renal ultrasound and on the presence of an elevated white blood cell count. Cystoscopy showed bladder inflammation but no masses. Cytologic analysis of urine obtained a t cystoscopy was negative for malignant cells. Fungal cultures were positive for Candida albicans. Bilateral nephrostomy tubes (Medi-techBoston Scientific, Watertown, Mass) were placed, and nephrostograms showed bilateral hydronephrosis, high-grade distal ureteral obstructions, and multiple small ureteral nodules 2-4 mm in dimension (Fig 1). Follow-up nephrostograms obtained 3 weeks later after a short course of intravesical amphotericin B (50 mg/L five times per day for 3 days) and a 3week course of oral fluconazole (100 mg per day for 3 days then every other day for 21 days) showed persistent obstruction and no change in the ureteral filling defects seen on the previous study. The right nephrostomy catheter was exchanged for a 10-F peel-away sheath (Medi-techBoston Scientific). Through this sheath, a 10-F over-the-wire Simpson atherectomy catheter with a 9.3-mm working diameter was advanced into the midureter in a region that contained numerous filling defects. The positioning balloon of the atherectomy catheter was inflated, and several shavings were obtained (Fig 2). The patient then underwent bilateral placement of internal double-J ureteral stents. The tissue samples were submitted to the pathology laboratory for histologic analysis. The samples were stained with hematoxylin-eosin stain, which revealed grade I1 papillary transitional cell carcinoma (Fig 3). The diagnosis was later corroborated by means of bladder biopsy performed during repeated cystoscopy; biopsy results indicated a diagnosis of grade I11 transitional cell carcinoma.