[A case of ammonium acid urate urinary stone]

We report a case of ammonium acid urate urinary stone. A 32-year-old woman with no past medical history presented with right back pain. The kidney-ureter-bladder X-ray and computed tomography revealed right ureteral and bilateral renal stones. The right ureteral stone was excreted spontaneously without treatment. The left renal stone was too large to be excreted and required extracorporeal shock-wave lithotripsy (ESWL). The analysis of the excreted stone revealed that it consisted of pure ammonium acid urate. Flakes of the left renal stone by ESWL were impacted in the left lower ureter and also rapidly grew in the left kidney. The right renal stone grew rapidly and right hydronephrosis developed due to the newly-formed right ureteral stone. As post-renal acute renal failure developed subsequently, ureteral stents were placed bilaterally. We finally treated the bilateral ureteral stone with transurethral ureterolithotripsy, the right renal stone with ESWL and the left renal stone with percutaneous nephrolithotripsy. During the course, dietary instruction was intervened for hyperuricemia. Although there were a few stones left after ESWL, they were halfway excreted without rapid growth of stones.