You asked about cranberry extract, well in my Odie's case he had struvite crystals. I changed his diet to wet and along with the meds from my vet. But the meds made him sick. I thought too of cranberry. I did some research and found Solid Gold's berry balance. It's a powder I sprinkle on his food once a day. In the beginning I gave it to him at both feedings then bumped it down to once a day. It worked. The ingredients are just cranberry and blueberry. Within a week he had no more blood in his urine and stopped marking everywhere. Rechecked him and he was clear. I've had him on it for a year now. I realize you are dealing with a little different situation here, but you can check it out and see. And the more moisture in the food the better.
