What Causes Swelling In Side Of Scrotum With History Of Vasectomy?

Sir, I m an Australian & 68 years of age. I had a vasectomy over 25 years ago & have had no side effects. However in recent months I have noticed that I have a considerable swelling in my right side of my scrotum. It isn t painful, but when I try & feel my right testicle, it is hard to actually feel.