Fluid around kidneys

Had another ultrasound today at 28 weeks to finish getting all the needed measurements they couldn't get at 21 weeks. At my follow up with the doctor she said that the baby still has a little fluid around the kidneys, wasn't told this with the last US. She said she wasn't worried about it just wants to monitor it so I have another US scheduled in 5 weeks. Has anyone else been told their baby has fluid around the kidneys. Everything else has measured normal and baby is in the 48th percentile for growth.