[1] Stanford Univ, Med Ctr, Dept Urol, Stanford, CA 94305 USA
[2] Stanford Univ, Sch Med, Dept Urol, Male Reprod Med & Surg, 300 Pasteur Dr,A259B, Stanford, CA 94305 USA
[3] Stanford Univ, Sch Med, Dept Obstet & Gynecol, 300 Pasteur Dr,A259B, Stanford, CA 94305 USA