If sperm cells are not identified in a ejaculated semen sample, this condition is called azoospermia. In the general population, 1% of males are azoospermic. In infertile males, 1-5% of them are azoospermic.
There are two major types of azoospermia, Obstructive Azoospermia (OA) and Non-Obstructive Azoospermia (NOA). Obstruction along the ejaculatory duct leads to Obstructive Azoospermia. On the other hand, Non-Obstructive Azoospermia has several etiologies, such as Sertoli cell only syndrome, maturation arrest, Klinefelter syndrome, testicular atrophy or hypospermatogenesis. Both types of azoospermia need surgery to retrieve sperm cells. OA and NOA can be differentiated based on history, testicular exam, FSH levels, and testicular biopsy findings. Males with normal testicular volume, normal FSH and normal testicular biopsies are suggestive of OA. Males with reduced testicular volume, elevated FSH, and testicular biopsy showing compromised spermatogenesis are suggestive of NOA.
For OA males, the chance of sperm recovery after surgery is excellent. For NOA males, the likelihood of sperm recovery is reduced when he has elevated FSH level, small testicular volume, AZFa or AZFb microdeletion. On average only 50% of NOA males will yield sperm cells after surgical procedures.