My son 4,5 years old has diagnosed with communication hydrocele in testicles. no pain, only swollen not very. is necessary surgery or we can wait?

Could wait, but: The risk of waiting is that a hernia could develop and in kids this can easily get trapped(incarcerated) and then become an emergency situation. Also, communicating hydroceles very rarely close on their own, unlike non-communicating ones where you can actually sit and wait and hope they go away. So you really are probably delaying the inevitable ad risking incarceration and an emergency situation.

Yes, ....: Yes, please proceed with surgical correction since professional experience has proved such inborn communicating hydrocele will almost be certain to last forever if not closed by age of 1. Besides, it is also associated with a small hernia (indirect). So, getting its surgical correction through a small inguinal incision like one for inguinal hernia repair is the choice of care. Best wish for him..