Xanthine urolithiasis causing bilateral ureteral obstruction in a 10-month-old cat.

Xanthine urolithiasis was diagnosed in a 10-month-old intact female domestic shorthair cat presented with acute renal failure due to bilateral ureteral obstruction. Ultrasonography revealed the presence of multiple uroliths in both kidneys and ureters that were not detectable on previous survey radiographs. Medical management failed and ureteral obstruction persisted with no evidence of stone migration into the bladder. Bilateral ureterotomy with urolith removal was performed in order to relieve the obstruction. The cat recovered from surgery, and blood urea nitrogen and creatinine values decreased within normal limits 6 days postoperatively. Urolith analysis by infrared spectrometry determined xanthine composition, and a higher blood and urine concentration of hypoxanthine and xanthine was also found. At 1-year follow-up, the cat was free of clinical signs. However, ultrasonography of the abdomen revealed small-size calculi in both kidneys, despite the low protein diet intake. The very young age of the animal suggests a possible congenital xanthinuria.