Hi. I'm Dr. Gotthelf. I have been a vet for 33 years and I would like to use my experience to help you with your pet's medical problem.
i hope there is more to the answer than that...
Most trade name brand cat diets for medical diseases are low magnesium and low pH foods. So the diabetic diet will promote an acid urine, which is not good for a ammonium urate stone cat. Unfortunately, the diet for diabetes will not work for your stone cat and you may need to use a different diet altogether for the stone cat. Even the commercial stone diets are not good for ammonium urate stones.
I have the diabetic cat on Urinary SO and the stone cat on KD.
It's almost unbearable to have two separate diets.
Here is a recipe for the stone cat:
Adult Cats with Urate Calculi
Cottage Cheese and Potato Diet
2/3 cups cottage cheese, 2% fat (151 grams) 1 cups potato, cooked with skin (123 grams) 1 tablespoon vegetable (canola) oil (14 grams) 1/4 teaspoon bone meal powder (1.5 grams) 1/5 multiple vitamin-mineral tablet (made for adult humans) 50 mg taurine
provides 397 kcalories, 23.7 g protein, 17.3 g fat see tables for a cat's caloric needs
For the diabetic cat, a diet that is low in carbohydrate and high in protein and fat is recommended....not k/d which is very low in protein. There is a food call Feline DM diet that I use for my diabetic cats.
I wish there was better news, but these 2 diseases require completely different types of foods.
I guess we were wondering the chances of the diabetes reoccuring - with and without a special diet - since it was caused by dexamethasone, which he is not on any more.
Dexamethasone does not CAUSE the diabetes. Your cat was probably pre-diabetic and the dexamethasone tipped her into full blow diabetes. Have you had her tested for glucose to see if she is still diabetic? If she is not, then she can eat the same food as the other cat.