Dehydration plus increases of serum uric acid. Double whammy, bad news. Staying hydrated is your best defense.
Fasting beyond ~3 days also increases the risk of gallstones, you can take some coconut oil (or any saturated fat) to clear the bile from your gallbladder and mitigate the risk. While technically not “true” fasting at that point, fat doesn’t trigger mTOR. So metabolically speaking you’re still in a fasted state even after 50-100 calories of saturated fat.