Azoospermia meaning absence of Sperm in the semen. This can commonly Obstructive Azoospermia because of block in the epididymis or in the vas either because of injury, infection or surgery. Azoospermia could also be caused by failure of production of sperm called Non obstructive azospermia. In these case Sperms can be retrieved by surgical techniques.
Microsurgical Epididymis Sperm Aspiration (MESA): By this technique epididymis is opened by fine dissection and sperms are aspirated by a fine needle from the epididymis. It is a day care procedure, done in the operation theater with facility of sperm freezing.
Testicular Sperm aspiration (TESA): This is similar to the other technique but the testes is aspirated from the testes. Finding good number of sperm in testes is not as good as in epididymis.
Sperm extracted in these methods are frozen and later used for Intra Cytoplasmic Sperm injection ICSI.