XOIs, including allopurinol, inhibit the production of oxygen radicals derived from xanthine oxidase [38], and therefore, their effect on preventing EI-AKI does not eliminate another hypothesis that EI-AKI in RUHC patients is the result of vasoconstriction induced by the oxidative stress that develops during exercise to exhaustion, which would be largely prevented by a normal concentration of UA, which is a powerful antioxidant [39]. Here, XDH is linked to acute kidney injury.