When I was pregnant with ds I was diagnosed with hydronephrosis(dilation of the ureter), had a stent put in, had the stent removed and was told that the condition would resolve itself after I delivered. Well, that mostly happened and the pain was there for a while and then went completely away. Now recently the last couple weeks I've been having pain the same pain again. I can't imagine why this would be happening since the reason for the dilation in the first place was a blood vessel blocking drainage and that was because of the baby pressing on it.
It's not an unbearable pain by any means. More of a nagging ache but I worry about damaging my kidneys if it is blocked again for some reason.