Hi. The condition is actually called pelviureteric junction obstruction or PUJO for short. While very mild cases can get better on its own, if one kidney is bigger than the other it means that the blockage is bad enough that all the urine is trapped in one kidney. If untreated this will cause the affected kidney to be irreversibly damaged and even fail. I understand your concerns about anaesthesia but this is a situation where it is necessary and the benefits of surgery definitiely outweigh the risk of anaesthesia.
I think you should talk to the surgeon at KK again about your concerns if you are still not sure. Traditional medicine cannot cure this and may in fact worsen the kidney even more so I suggest you dont't do that. This is a serious condition and is better treated early rather than late.