[A Case of Pyonephrosis Due to Urethral Stent Forgotten for 4 Years].

A 53-year-old woman had left pyonephrosis and bladder stone. A double-J ureteral stent was placed for left ureterostenosis and she was lost to followup. Five years later, she had back pain. Computed tomography revealed left hydronephrosis, pyonephrosis and bladder stone. After drainage by percutaneous nephrostomy and antibiotic treatment, left nephroureterectomy was performed. She has been free from recurrence of infection for 3 months after the surgery.