PESA is the short form of Percutaneous Epididymal Sperm Aspriation. It is done without any surgical incision. A small needle is passed into the epididymis through the scrotal skin and the fluid is aspirated. Then the sperm cells are retrieved from the fluid and prepared for further tests.
Microsurgical Epidydmal Sperm Aspriation (MESA) is used in conditions where sperm count is very low. A microscope is used for making an incision of a single tube is done. The fluid that spills gets pooled and this fluid is then collected.
TESA & TESE
TESA is actually Testicular Sperm Aspiration and TESE is Testicular Sperm Extraction. TESA is done by inserting a needle in the testis and aspiration the fluid while TESE is a surgical biopsy of the testis. The fluid thus collected is sent to the embryology laboratory and the sperm cells are collected.