Microsurgical Epididymal Sperm Aspiration (MESA) is used in male infertility conditions like obstructive azoospermia, involves dissection of the epididymis under the operating microscope and incision of a single tubule. MESA is performed in the operating room with general anaesthesia utilizing the operating microscope. Patients usually cryopreserve sperm during this procedure for future IVF/ICSI. MESA allows for an extensive collection of mature sperm as compared to aspiration techniques.

TESA or testicular sperm aspiration is performed by inserting a needle in the testis and aspirating fluid and tissue with negative pressure. The aspirated tissue is then processed in the embryology laboratory and the sperm cells extracted are used for ICSI.

MESA treatment gives the highest number of sperm, with a hundred times more sperm being recovered compared to TESA and percutaneous biopsy.