I tried many things and this helped me, and when I did it, something like sludge was passed, I am doing this flush monthly to avoid further stones. Someone passed this on to me:
Appalachian kidney stone Flush.

Required: 6 pack of Classic Coca Cola ®, one 1 pound can of Asparagus.

Directions: Drink 1 can of Coke every 20 minutes (takes two hours). Eat the can of cooked Asparagus and drink the juice immediately after drinking the last Coke. I put the asparagus in the blender and made it like a soupy mixture and ate it like soup. Retain all fluids for as long as possible before eliminating. Drink a minimum of 64 ounces of pure filtered/distilled water throughout the next 24 hours.

The naturopath who shared this with us has seen some dramatic successes using this folklore recipe.