Significance of subclinical varicocele detected by scrotal sonography in male infertility: a preliminary report. 
To assess the clinical significance of subclinical right varicocele, we used scrotal sonography for a prospective study of 68 infertile patients with a clinical left varicocele.  A significant difference was found in the improvement in postoperative semen characteristics between sonographically diagnosed bilateral and unilateral groups.  We conclude that a subclinical right varicocele is also detrimental for spermatogenesis in patients with a clinical left varicocele.