Secondary Oxalosis Involving the Epididymis

A 46-year-old man presented with a 1-month history of fever. He had undergone peritoneal dialysis for 7 years to treat endstage renal disease and underwent renal transplantation in 2006. For 10 days, he presented with minimal scrotal swelling and discomfort. Ultrasonography showed that both testes were normal in size and had normal echogenicity, but the right epididymis was enlarged, showing more echogenicity than the left one. Serologic and urologic analyses were both negative. Cytologic findings for urine showed many bland-looking urothelial cells with acute and chronic inflammatory cells, and amorphous crystalline materials (arrow) with birefringent activity under the polarizing microscope (Fig. 1). The patient underwent right orchiectomy for a presumed epididymal tumor. On gross examination, the excised testis measured 3.5×2.3×1.5 cm and weighed 22 g. The cut surface of the testis appeared normal. The attached epididymis measured 4.5×1 cm. On sections, the head portion of the epididymis revealed a pedunculated reddish tan soft mass with partial cystic dilatation (Fig. 2A, arrow). On microscopical examination, the testis was found to be composed of seminiferous tubules with active spermatogenesis. The epididymis revealed multifocal deposition of amorphous crystalline materials, with cystic dilation of the epididymis and ductuli efference (Fig. 2B). The stroma adjacent to the excretory ducts showed a foreign-body giant-cell reaction with an accumulation of crystalline calcium oxalate deposits (Fig. 2C). The amorphous laminated crystalline materials were birefringent under a polarized light microscope (Fig. 2D), which confirmed secondary epididymal oxalosis following long-term dialysis.