Slightly abnormal ultrasound @ 31 weeks

31 week growth ultrasound today, and everything looked/measured great/normal... except a pocket of fluid around one of Baby Girl's kidney. The Doctor who came in wasn't particularly informative, and just said that it could resolve itself or it could be something like an ovarian cyst. Not a whole lot of positivity, though, judging from his personality... but that could've just been his personality.

I just read that fluid around the kidney may be a soft marker for Downs??? I was blood tested (NIPTS) and did the nuchal fold ultrasound at 14 weeks, and our risk was extremely low.

Anyone have experience with this, this late in the game?