Re: Kidney Cleansing

He recommends majoram, cat's claw, 

If he is passing kidney stones then cat's claw is not a good idea. Cat's claw is high in oxalic acid, which can lead to calcium oxalate kidney stones.

comfrey root

Comfrey root eeds to be dried and aged at least 2 months before internal use to destroy the pyrrolizidine alkaloids that are toxic to the liver.

uva ursi

Uva ursi should not be combined with other herbs as its high tannin content will bind many of the active components in other herbs rendering them useless to the body. This is the most common formulating mistake I see made. In addition uva ursi should not be used longer than 4 days without a break to prevent irritation to the kidneys.  It also needs to be taken with a little calcium citrate or baking soda for the 2 hydroquinones generated by uva ursi to function properly.

Personally I think magnesium malate, couchgrass, cornsilk, parsley leaf, green apples or other malic acid source and watermelon are much better choices. Although I do agree with gravel root.