Pelvic kidney single umbilical?

So at 19 weeks during my anatomy scan I was told baby b had a single umbilical artery. I was told not to stress due to the fact that it's mostly common in multiples. Today at 26 weeks for our monthly ultrasound, I found out baby b only has one functioning kidney but there could be a possibility that the kidney stayed in the pelvic area. Has anyone else heard of this? I'm just really concerned for baby b growth.