the absence of sperm in ejaculated semen, is the most severe form of male factor infertility and is present in approximately 5% of all investigated infertile couples.
The condition is currently classified as "obstructive" or "non-obstructive", although it is important to also consider the specific aetiology of each individual case.
Some cases of obstructive azoospermia are treatable using microsurgical reconstruction of the seminal tract (for example, vasectomy reversal).
Unreconstructable obstructive azoospermia and non-obstructive azoospermia have historically been relatively untreatable conditions that required the use of donor spermatozoa for fertilisation.
The advent of intra-cytoplasmic sperm injection (ICSI), however, has transformed treatment of this type of severe male factor infertility.
Sperm can be retrieved for ICSI from either the epididymis ( MESA ) or the testis (TESE) depending on the type of azoospermia.