Azoospermia is defined as the complete absence of sperm from the ejaculate without implying an underlying cause. This condition is present in approximately 1 % of all men and up to 15 % of infertile men [285, 286]. Azoospermia may result from mechanical blockage occurring anywhere along the reproductive tract, including the vas deferens, epididymis, and ejaculatory duct, but most often it is associated with a spectrum of various severe and untreatable conditions causing an intrinsic testicular impairment, which is termed non-obstructive azoospermia (NOA) [287]. Varicocele is found in 5 % of men with NOA, but its absolute impact on the azoospermic status is still unknown [230]. The advent of assisted reproductive technologies (ART), particularly intracytoplasmic sperm injection (ICSI), has reintroduced the awareness about varicocele with NOA, as improvement in testicular function to obtain viable sperm for ART may be critical for infertile men with NOA.

Genetic evaluation including karyotype and Y chromosome mapping are crucial in the work-up of men with varicocele and azoospermia. Microdeletions of the Y chromosome (YCMD) can be identified in up to 18 % of these men [286]. Molecular diagnosis and subtyping of Y-chromosome microdeletions (YCMD) have been useful markers not only to detect the males in whom NOA is caused by YCMD, but also to counsel the affected patients about their chances of sperm retrieval success. Furthermore, the affected patients should be aware of abnormalities so that they can obtain genetic counseling in order to quantify their risk of transmitting them to their offspring. Finding a microdeletion within the AZFa or AZFb regions practically implies that the chances of SR success are virtually non-existent. Therefore, it would be unreliable to recommend varicocele repair in such cases [288, 289].