Is surgery necessary to treat kidney inflation?

Hi doctor,

My son is suffering from left kidney inflation. The doctor instructed us to have a follow up with abdomen and pelvic ultrasonography. When my son was 9 months old, his left kidney got enlarged measuring 2.6 inches. We visited another doctor who instructed us to keep following up with an abdomen and pelvis ultrasonography for six months. When my son was 1.5 years old, the report showed ballooned left renal pelvis with 30 mm in the maximum dimension, associated with mild calyceal dilatation and a 3.5 mm in the left lower calyceal stone was detected, an average caliber of the left ureter suggestive of left PUJ obstruction. But clinically, both the kidneys were of average size and shape. When my son was 1 year and 8 months old, we took a renal isotopic scan. I have attached the report. My son is not having pain. I do not think that this is a severe condition to undergo a surgical operation. Now my question is whether my son is still suffering from inflation of the left kidney or not? If yes, is it possible to get cured by medicine or it needs surgery? What is the calyceal stone, and is it harmful to my son? Is there any treatment by medicine or it must be cured by surgery? The doctor whom I follow told that my son needs to undergo a surgical operation to widen the ureter. Is it true? Should he need surgery?