A nephrologist is a kidney specialist, that's why I asked if you were seeing one as well as urology- we've done both.
If you know he's going to need to go and be seen, I'd call the pediatrician now and get the referral going, that way you can go ASAP. I know my cousin's son had a kidney problem that was diagnosed in utero and they actually met with the specialists before he was even born. He wound up being very lucky and it cleared up on it's own, so that part was nice. I hope that you have similar good luck
With my son, we never knew anything was wrong until he was about 8 or so months old and just started peeing blood. Bright red blood. Took him to the ER on a Sunday night, the first time it happened. They cathed him, didn't see anything in the sample and sent us home with basically "stuff happens" as the diagnosis. I planned to follow up with his ped. anyhow, but it happened again the next day. I called the office and asked what I should do and they said go back to the ER and refuse to leave until we saw someone from urology. So, that's what we did. We saw the urologist in hospital that day (we have a children's hospital nearby and they have all the peds. specialists right there). Anyhow, we saw them, he saw no immediate dangerous things and scheduled DS for an office visit two days later but said to come back if it increased in frequency or volume.
We went to the follow up appointment and he had a lot of testing done and finally wound up with exploratory surgery via cystoscopy (scope up his parts). They found, broke up and removed kidney stones. But of course the question is why is an infant having kidney stones? That was when we got the nephrology referral. They never really did find out why he was having the stones but since they resolved and didn't appear to come back we left well enough alone.
Fast forward a few years and now the poor kid cannot pee- seriously, he could barely get anything out and it would take him FOREVER to pee. I happened to notice because he came in while I was in the bath to go to the bathroom. We tried to deal with the more local children's hospital but they weren't going to be able to get him in for months and in the meantime he is getting worse and worse. That was when we went looking for bigger and better and headed up to Boston. Total PITA with the two hour commute each way but you do what you have to do. He had a lot of testing done and he had surgery up there this past July. He had some strictures (narrowing) and structural problems fixed. Luckily, the kidney stones had not returned. We went back and did follow up and everything is good for now, but we will be monitoring this for basically the rest of his life, it's unknown if this will happen again (the structural problems and/or the stones). We will be sticking with the urologist at Boston Children's for future needs, and will see a nephrologist up there too should the need arise. They are just much more on top of things than our CT hospital is, unfortunately
My son also took a lot longer to potty train than his twin or my oldest did and until just recently still had nighttime problems. We think that a lot of this was related to his problems and his urologist in Boston agrees.
Anyhow, sorry that was so long. I'll be thinking of you and wishing you the best. I hope everything clears up for your son
I'm coming to terms with the fact that I will not know everything and just need to take things as they come 
EeyoreEma!!! 
