Abstract
【Introduction】Matrix stones are a rare form of urinary tract calculi, and they are very difficult to definitively diagnose using conventional diagnostic imaging techniques. We report a case in which urinary tract matrix stones led to a suspicion of urinary tract tumors in a patient on maintenance hemodialysis. 【Case report】A 63-year-old man had been on maintenance hemodialysis for 34 months because of end-stage chronic kidney disease caused by diabetes mellitus nephropathy. He developed asymptomatic gross hematuria. Computed tomography detected hydronephrosis due to a tumor in the right upper ureter. Magnetic resonance imaging demonstrated tumors in the right renal pelvis and right upper ureter. Retroperitoneoscopic right nephroureterectomy was performed. However, instead of tumorous lesions, black-colored calculi were observed in the renal pelvis and ureter. Histopathologically, the resected specimen showed regenerative and hyperplastic epithelial changes without malignancy. An analysis of the calculi indicated that the matrix stones were entirely composed of protein. 【Conclusion】Clinicians should consider the possibility of matrix stones when a ureteral tumor is suspected on conventional diagnostic images in patients on maintenance hemodialysis.
