Torsion of undescended testis in a man with Down's syndrome.

Undescended testis is one of the most common disorders in Down's syndrome. We present an extremely rare case of torsion of an inguinal undescended testis in a 35-year-old patient with Down's syndrome. Surgical exploration revealed a rotated gangrenous testis, radical orchiectomy was performed, and pathological examination confirmed the diagnosis of testicular torsion.