The location of an epididymal repair (distal, mid or proximal) is determined by specific findings at surgery. The standard approach Dr. Finnerty has used in the past has been to leave as much epididymis as possible, to maximize both storage capacity and length for sperm maturation. But his experience has been that this often leads to technical success with poor sperm motility. The reason for this is twofold:
1) The presence of non-motile or degenerating sperm in the mid or distal epididymal fluid does not prove that you are above the obstruction. When fluid is sampled from a point higher in the epididymis, the transition is often striking — you go from no active sperm to 70% active sperm or greater. There is usually a visual transition zone above which this change is seen.
2) In the normal, unobstructed epididymis, motility/fertility is not seen until you get more distally (lower) in the epididymis. In the obstructed epididymis, however, motility is seen much more proximally (higher), suggesting that a change in the physiology of the epididymis occurs after vasectomy. This is why aspiration in the proximal epididymis produces better quality sperm for IVF.
There is a trade-off to doing a VE more proximally: less sperm storage capacity. But the advantage is that by going high enough to find motile sperm when possible (not always there, unfortunately), postoperative sperm counts show substantially better motility. This was the rationale for Dr. Silber’s approach of sampling fluid until motile sperm are found; that is Dr. Finnerty’s experience as well.
Epididymal repairs are not automatically performed in the upper portion of the epididymis, but if possible at a point where motile sperm are present. If that is in the mid-epididymis or lower, that’s where the repair is performed. In Dr. Finnerty’s experience, however, it often ends up being in the upper 1/3.