Both kidneys shrinking 25%, what is the treatment for this?

None: Shrinking kidneys are a sign of scar tissue developing in the kidneys. There is no treatment that reverses the scar. The are treatments to slow the loss of kidney function. It is important to find out what is causing your kidney injury in the first place. General treatments are avoid tobacco, low sodium diet, low protein diet, good BP control, good cholesterol control and avoid obesity.