I made sure that my kidneys were working well by having Celery Seed Tea for a couple of weeks. I think my kidneys are working fine as I don't get any discomfort with the flush and have always had good water works.
The primary reason for flushing is because of a condition called biliary sludge which is common in people with a spinal injury like me. This wasn't diagnosed until I had completed a dozen flushes as before then I just knew it a gall bladder pain.
However, flushing has been very beneficial in reducing and clearing up a whole load of Fibromyalgic type symptoms that I had suffered from for years. At the moment I only want to do Liver Cleansing and when that is complete to my satisfaction I may consider something else. I think it is wise to carry out only one cleanse at a time.