Testicular Torsion

My 15 year old son woke up in the middle of the night feeling severe pain in his left testicle and left abdomen. The ER doctor diagnosed it as testicular torsion. She gave him pain killer and tried to untwisted his testis. But my son felt so much pain, so she stopped and called the urologist surgeon. During the ultrasound exam, my son suddenly announced that the pain was gone. Ultrasound revealed that his testis looked slightly swollen, but sufficient blood flow in both testis. Urine test showed no infection. At the ER room, surgery was highly recommended. But we didn't proceed to surgery. Later we went to a childrens' urologist, and he also recommended a selective surgery in order to prevent it from happening again.

I'd like to know if it happened once, will it increase the chance of it happens in the future?  The torsion "self-corrected" by itself. Now everything is normal. Is surgery a good option?