[DRUG-INDUCED BILATERAL NEPHROLITHIASIS IN AN ULCERATIVE COLITIS PATIENT: A CASE REPORT]

A 59-year-old female experienced gross hematuria and right back pain, and she visited our hospital in March 2015. Abdominal computed tomography (CT) showed bilateral renal pelvic calculi; the right stone was 15 mm and the left stone was 18 mm in diameter. She had ulcerative colitis and had been taking salazosulfapyridine (SASP) for about 30 years. Urinalysis showed aciduria and deposition of urate crystals. An abdominal X-ray picture did not show a calculus shadow. We suspected uric acid calculus and started treatment with urinary alkalizer and uric acid production inhibitor.Three months later, abdominal CT showed enlargement of the bilateral renal pelvic calculi; the right stone was 25 mm and the left stone was 24 mm in diameter. She also complained of worse right back pain and underwent transurethral ureterolithotripsy for the right renal pelvic stone. The stone was orange, comparatively soft, and chipped down until it was approximately half of its original size. The stone analysis suggested suspected drug-induced urolithiasis, but not uric acid calculus. Thus, we investigated the stone and SASP using infrared spectroscopy, and the infrared absorption pattern was similar in both. The stone analysis demonstrated drug-induced urolithiasis induced by SASP.The patient's ulcerative colitis therapy was switched to mesalazine, and the amount of urinary alkalizer was increased. Abdominal CT 3 months thereafter showed dissipation of bilateral renal pelvic calculi. The patient did not take any preventative medication, and there was no recurrence of urolithiasis.