I am sorry Maddie has stones.
You can read about them here:
Here is a recipe for homemade treats made from renal food:
Yield: approx. two dozen treats
Using canned food:
For a conventional oven, follow the instructions above and place the bite-sized pieces on an ungreased cookie sheet and bake at 350 degrees for approximately 30 minutes or until crispy.
Using Dry Food:
To enhance flavor, sprinkle oregano powder over the dry food treats. However, do not add oregano to homemade treats when Prescription Diet® z/d® or d/d® foods are used. Cookie cutters make treats fun to make and serve. Only Prescription Diet® a/d® Canine/Feline food, Prescription Diet® n/d® Canine and Prescription Diet® s/d® Canine foods cannot be made into homemade treats using the above recipe. However, you can use the following recipe for homemade treats for these foods:
I hope Maddie enjoys them./
Best wishes for her,