The Anatomy of the Vas Deferens.
The vas deferens is a long tubular structure that carries sperm from the testicle up through the scrotum and into the deep pelvis. From there, the vas deferens wraps around behind the bladder and then through the prostate gland where it enters into the urethra.
During a vasectomy, this tube is divided and sometimes a piece is removed. The ends are then sealed off using some combination of either clipping or tying the ends, cauterizing (burning) them, and sometimes also burying an end under another layer of surrounding tissue. These maneuvers are used to prevent the ends from growing back together again during the healing process.
The goal of a vasectomy reversal is to surgically re-establish the flow of sperm from the testicle through the vas deferens. Precise surgical technique is essential in order to prevent scar tissue from re-blocking the channel after a reversal, since the vas deferens is quite small, with an outer diameter of only 2-4 mm (in comparison, a standard #2 pencil has an outer diameter of 6-7 mm). The walls of the vas deferens are thick and muscular so the lumen (the inside channel where the sperm travel) is significantly smaller, with a diameter of only 0.3-0.5 mm (in comparison, the thickness of a standard sheet of copy paper is 0.1mm).
Vas-to-Vas or Vas-to-Epididymis
There are two ways in which a vasectomy reversal can be performed. One option is to attach one end of the vas deferens to the other, which is called a vasovasostomy (or “vas-to-vas” connection). The scarred, blocked areas(where the vas deferens had been cut, tied, burned, etc. during the original vasectomy procedure) are removed during the reversal procedure so that fresh healthy tissue is brought together for optimal healing.
The other option is to connect the vas deferens to the epididymis, a procedure which is called a vasoepididymostomy (or “vas-to-epididymis” connection). The epididymis is the structure that wraps around the side of the testicle, and is where sperm maturation takes place. The epididymal tubules are smaller than the vas deferens, and therefore it takes less scar tissue to block them off. A vas-to-vas connection has a higher chance of success, and is always performed if possible.
Choosing Vas-to-Vas or Vas-to-Epididymis
Until the time of the reversal, it is not known whether a vas-to-vas or vas-to-epididymis connection will be needed. The decision is made by examining the fluid that comes from the end of the vas deferens going towards the testicle when it is opened during the reversal procedure. A drop of this fluid is placed on a glass slide and examined under a tabletop microscope in the operating room. Vasal fluid is checked individually on each side. Favorable fluid (clear or thin and milky in appearance, sperm/sperm parts present) indicates that the connection flowing from the testicle to the site of the prior vasectomy is not blocked and a vas-to-vas connection can be performed. However, if thick creamy fluid without sperm is found, then one of the delicate epididymal tubules has ruptured under the back-pressure. An epididymal rupture typically does not cause any symptoms (such as pain) but does block the transport of sperm beyond the rupture site. When this occurs, a vas-to-epididymis connection is needed, and the vas is attached onto the epididymis where sperm are again found in the epididymal tubules above the rupture site. If the surgeon does not know how to perform a vas-to-epididymis connection in this scenario, then the procedure almost certainly will not be successful on this side.
The chance of needing a vas-to-epidiymis connection increases with the amount of time that has passed since the vasectomy was performed.