Kidney Failure: Kidney disease is probably the leading cause of mortality in the cat. It is troubling to think about the role that chronic dehydration may play in feline kidney failure. And remember, cats are chronically dehydrated when they are on a diet of predominantly dry food. The prescription dry 'renal diets' such as Science Diet k/d - which is commonly prescribed by veterinarians - contain only a small amount of moisture leaving your cat in a less than optimal state of water balance.
I must say that I find it truly amazing when I hear about the very large numbers of cats receiving subcutaneous fluids while being maintained on a diet of dry food. This is extremely illogical and every attempt should be made to get these cats on a diet that contains a higher moisture content. Please also note the following list of the first four ingredients of Science Diet dry k/d after reviewing this section on reading a pet food label - and bearing in mind that your cat is a carnivore. This is a diet that would never find its way into a food bowl owned by any cat in my care.The first three ingredients are not even meat and the fourth ingredient is a by-product meal.
Brewers rice, corn gluten meal, pork fat (preserved with mixed tocopherols and citric acid), chicken by-product meal
The purpose of this prescription diet is to restrict protein which, unfortunately, it certainly does. However, please understand that there are no studies showing that it is beneficial to feed these patients low protein diets. k/d restricts protein to the point that the cat will often catabolize (use for fuel) his own muscle mass which results in muscle wasting and weight loss. The level of protein in this diet is not only at an extremely low level, it is in an incomplete form for a carnivore. Note that it is made up mainly of plant proteins - not meat proteins.