I have a vacuole on the bottom/backside of both testicles. should i be concerned, they are not noticeable until i am inspecting them?

Testicular self exam: You are probably palpating your epididymis on both sides. Men should know what the epididymis feels like: a soft cord on the back of the testicles. I have attached directions for you from the NIH. If you feel something hard, different, have family history of testicular cancer or personal history of an undescended testicle, see a Urologist https://www.nlm.nih.gov/medlineplus/ency/article/003909.htm