The first portion of the sperm duct is known as the epididymis. The epididymis is about 1.5 inches long, is attached to the testes, and contains about 20 feet of coiled, microscopic sperm ducts. Sperm become mature and active (acquiring motility) in the epididymis after they leave the testes.
After vasectomy, some men will develop a leak of sperm fluid from one of these delicate tubes, which results in inflammation and scar tissue formation, resulting in a second obstruction point in the epididymis. The chances of this occurring increase with the number of years after vasectomy, although it can occur at any time after vasectomy.
If this blockage is not repaired at the time of vasectomy reversal, the sperm duct will remain obstructed and the reversal will fail. The tubule in the epididymis is even smaller than the inside channel of the vas (about 0.1 to 0.2 mm in diameter), and it has an extremely thin wall. Repair of a blockage of the epididymis is impossible without microsurgery. Microsurgical vasoepididymostomy (VE) is the most technically demanding procedure performed in surgery, in any specialty, and considerable surgical experience is required to get reliable results.
The need for a vasoepididymostomy can only be determined at the time of surgery, by evaluating the fluid from the testes for its appearance and the presence or absence of sperm. Blockage of the epididymis may be seen on one or both sides.