How do you counsel a man with nonobstructive azoospermia and a normal FSH on his odds of successful sperm retrieval?

Such a nuanced question. Will assume 46 XY, no Y micro deletion, no varicocele to fix that would suggest late maturation arrest which may respond to varicocele repair. I would offer them testis mapping depending on testis volume. Say they want to go to mTESE without mapping—would discuss donor sperm back up and/or egg freeze if no sperm found. All that being said, quoting percentages can be tough, so I usually don’t—only that I’m going to keep looking until we find sperm or we’ve exhausted sites...

There is no easy answer. It depends upon testis size, his history, and his genetics testing. The success rate can range from 0->95%, depending on the situation.