My mother-in-law has a cat which she was feeding Eagle Pack food to. Her vet told her the cat had crystals in his urine and that he needed to be on a special diet. She got the new food from the vet. However, the first two ingredients in it are corn and wheat gluten??? She is worried about feeding her cat this. Does anyone have any suggestions for a food with a cat that has his symptoms. Also, can anyone explain to me what makes a cat get crystals in his urine and whether or not it's caused by the food they eat?