Thanks for the information SSN and I'm sorry you had a rough experience. Had you dry-fasted much before? Did you pass urine comfortably and frequently during the fast? I've passed urine daily and on some days stools during my fast. It might be helpful to the community if you posted your experience on say the curezone forum.
I experienced considerable flank pain during my first 3-day dry fast in Dec 2012 and some in possibly the following fast, but none since. I was and still am unclear whether it was kidney pain as many old injuries flared up and I had experienced lower back problems years before.
In the past, I've dry fasted only 1 or 2 days, altho I have juice fasted up to 9 days. Have also done several liver flushes over the last 30 yrs or so, as I also build up gallstones periodically (I think due mainly to oxalic acid in foods. I avoid spinach & chard now). Last yr I also started the dreaded coffee enema now and again w surprisingly good results.
Regarding my dry fast, passed urine comfortably for the 1st four days. I don't know about frequently, after all, I was dry fasting. Stones arrived on 5th day, which was the reason I broke fast w water, taken every 30-40 minutes until symptoms resolved after 4-5 hours. No problems w kidneys post dry fasting. May do a watermelon juice fast soon as we're going into summer. Watermelon contain a natural diuretic, May juice cucumbers as well, to cut down on high sugar content of juice and as I believe they also contain citrulline.
Thanks for tip about curezone. May post my experience there.