Excessive damage to vas by scarring from previous vasectomy
During vasectomy, the purpose is to irreversibly eliminate the fertility. Therefore the surgeons goes to diferent extents to achive this. They may remove long segment of the vas. Some surgeons put electric cautery needles into the opening of the vas and destroy about 1.5 cm on both cut-ends. This causes excessive scarring of the ends. These scarred areas need to be removed during the reversal while preserving adequate length for the reconnecting.
Disproportionate diameters of the vas cut-ends
As shown in the above picture, both cut-ends have openings(lumen) of different sizes. This is where the multilayer techniqe is more important. As you can see, the inner layer of the sutures are deployed taking extreme care to connect the inner layers first to give perfect alignment of the disproportionate sized openings of the vas.
Too thin vas cut too close to the epididymis
When the vas is cut close to the epididymis, it will be at the curly (convoluted) part of the vas. Thsi aport of the vas is very thin in its wall but will wider opening size. As the vas is curly, it may be difficult to get a clear circular end. Thsi is another situation, that can be helped by using very fine 9-0 or 10-0 sutures and multilayer technique.
The picture below shows the lower end is very thin as the cut was in the curly (convoluted) part of the vas
Even this thin lower end was nicely aligned by multilayered technique
Blow out or Obstruction at the level of epididymis
This is due to the rupture and blockage of the extremely fines tube in the elididymis that continues as vas. If there is a blockage at the level of epididymis, simply connecting the vas to vas (vaso-vasostomy ) will not be successful. It would be necessry to connect the extremely fine tube in epidydimis to the vas. This is a very challenging and time consuming procedure
Redo-reversals for failed previous reversals
In the picture below, the bluish stitches are the thick 6-0 sutures used in previous reversal from another centre. See how the thickness of that stitch compares witht he black coloured 10-0 suture.
The completed Redo-reversal by Multilayered technique as shown below.