Bilateral Hydronephrosis

We have had our 20 week ultrasound that showed severe bilateral hydronephrosis (dilation of both the kidneys). We have been referred to a specialist who won't see us until 26 weeks in 4 weeks time! We haven't been told what this could mean for our baby and are really anxious! I have heard that it can correct itself but this tends to be mild or moderate cases or where it is only in 1 kidney. Has anyone been through this that can share there story or outcomes?