 [ Symptoms ] what are aging spots [ Disease ] semen analysis is not suitable to diagnose prostate ca azoospermia has to be established before declaring sterility this re testing is most likely a part of that very protocol to detect any viable number that could lead to impregnation though vasectomy is very safe method and only 1  failure rate is there retesting at three weeks is ideal to confirm azoospermia wishing you best of health thanks