[Matrix stone: a case report].

Here, we report a case of matrix stone in a 32-year-old man with diabetes, gout, and chronic renal failure. The patient complained of pain in the left flank. He had undergone an operation for bilateral vesicoureteral reflex at the age of 17 and matrix stone discharge was repeated. Computed tomography revealed a soft tissue mass in the right hydroureter. Percutaneous ureteral lithotripsy was performed successfully. Analysis of the stone components revealed the stone to be composed entirely of protein. Radiological imaging of matrix stones may be difficult to separate from urothelial cancers.