Once crossing vessels have been ruled out, the most critical step during a pyeloplasty is cutting the diseased ureteral segment down to healthy ureter. Differentiating healthy from unhealthy ureter is not always easy though.
The high success of redo pyeloplasties likely has to do with having a better chance of reaching healthy ureter the second time around.
The video below exemplifies the challenge of identifying healthy ureter. On the video, you can see how the proximal ureter is very narrow and is even difficult to get one blade of the scissors in. The ureter remained narrow for a few centimeters and then a clear area of better and wider ureter was found. Thankfully the renal pelvis was large and reached down to the ureter.
I was tempted in this case to end the spatulation sooner as it seemed already fairly long. In the end, I was glad I didn’t do that.