The development of surgical sperm extraction and new challenges to improve the outcome.

Surgical sperm extraction with intracytoplasmic sperm injection has become widespread worldwide and is regarded as the sole option for patients with azoospermia. However, the sperm retrieval rate remains unsatisfactorily low, particularly for men with non-obstructive azoospermia (NOA). Therefore, the technical challenges associated with improving the sperm retrieval rate for men with NOA are being addressed. The most successful method developed to date is microdissection testicular sperm extraction (micro-TESE), which is rapidly becoming recognized as a useful technique due to its relatively high sperm retrieval rate and low complication rate. However, even with micro-TESE, the sperm retrieval rate for men with NOA remains at 30-60 %, with an even lower birth rate. The technical challenges associated with improving the outcomes of surgical sperm extraction are being approached through the use of ultrasound and optimal surgical devices such as narrow band imaging, multiphoton microscopy, and optical coherent tomography. In addition to the difficulties related to searching for sperm, medical treatments that induce spermatogenesis remain controversial. For example, varicocele repair prior to surgical sperm extraction and hormonal therapy before and after TESE have been extensively examined. We herein briefly summarized the development process in surgical sperm extraction up to the present and technical challenges to improve the outcomes of surgical sperm extraction.