In contrast to PESA and TESA, this is a surgical procedure where an incision is made in the scrotum, exposing the testis and the epididymis. An operating microscope is used to identifya single tube in the epididymis from which sperm can be aspirated.

MESA is done under general anesthesia and is generally performed for men with a non-correctable congenital problem, such as absence of the vas defer ens or obstruction in the epididymis. It helps in the retrieval of large numbers of high quality sperm which can be used for multiple IVF/ICSI cycles, or frozen for future use.

The above procedures are performed for men when sperm are being produced, even if in low numbers, but a blockage prevents their release. Men who have no blockage but have problems with sperm production will likely have no sperm in the semen.