Epididimytis is an inflammation of the epididimys, an elongated organ that hangs on the backside and off to the outside of the testicles.
Although the most common description you will find on the WWW will be for of acute epididimytis, the most common form seen in any urologist's office is that of chronic epididimytis. In the acute form the man develops a very intense swelling, redness and pain of one or bothe testicles in a matter of 1 or 2 days, often associated with burning and frequent urination, fevers and difficult urination which becomes a medical emergency at times requiring hospitalization.
With the much more common Chronic Epididimytis the man complains of a soreness that can lasts for days or weeks of the testicle and scrotum that bcan radiate to his lower belly. It is not usually associated with any significant swelling. It is not usually caused by bacteria and this is why antibiotics do not provide any significant relief.
If on physical exam or patient self exam there is a nodule or area of hardening, it is not unreasonable to get an ultrasound to rule out a testicular tumor, thought this is not found frequently.