[Polyorchidism: a case report and review of the literature].

An 11-year-old boy visited our department complaining of left scrotal painless mass from 6 months ago. The small mass was palpable beside the left testis. Ultrasonography shows isoechoic round shaped mass 5 mm in diameter. At surgery, the mass was connected with the left testis and epididymal head and sharply excised from them. Histological examination showed normal testicular architecture, but spermatogenesis was not found. We report the 18th case of polyorchidism in Japan and made some discussion about polyorchidism.