PESA is done under local or general anaesthesia with the specialist inserting a needle attached to a syringe into the epididymis (the tiny collecting tubules next to the testicles), then gently aspirating fluid. The epididymis is the structure into which the sperm first flow after developing and leaving the testicles.
PESA is used for men who have had a prior vasectomy and in those who have a congenital or acquired obstruction of the genital tract such as absence of the vas deferens. The sperm retrieved with this technique can only be used in conjunction with ICSI treatment.
Sperm may not always be obtained with the PESA technique and the specialist may have to perform an open procedure.