Does Acute Kidney Injury From an Ultramarathon Increase the Risk for Greater Subsequent Injury? An American group has studied 627 runners in a 100-mile runway whether damage to renal function increases by an ultra-rose risk for further kidney problems.
It showed that a slight kidney damage in ultra skiers is customary but this is not a problem for further runs. The very important result can be found under https://pubmed.ncbi.nlm.nih.gov/26657822/