Normal tests

Hey guys! So over the last year and half my doctor has been concerned about my kidneys because my eGFR has been low ranging from 65-77…she did a bunch of other blood & urine tests as well as a ultrasound which all came back completely normal despite the one low number. She said it should be well over 90….now she’s sending me to a kidney specialist but it feels like a waste of time. Any suggestions or insight? I don’t know much about the topic. Thank you!