@mfratt, hi! LOL, as someone with late stage CKD and close monitoring of gfr, sometimes I feel like grr!

Seriously, though, a lesion isn't always cancer but without knowing more, I have no answers except (if you haven't already) find a nephrologist and/or medical professional who can tell you more about what the lesion is and what it means and monitor your kidney function.

Was the specific gravity high or low? That can indicate dilute urine or dehydration, depending on the value.

It helped me rest my remaining kidney by following a renal health meal plan, plant based with no meat. Please don't consider this medical advice, it's just what I did to delay dialysis and, once I did have to go on dialysis, to suspend it after 6 months. Just my own experience here.

Good luck finding answers and welcome to Mayo support!