It is hard to hear information that conficts with your vet but we disagree. This is what the vet who contributes to this site says about kidney disease and food:
Kidney Disease (CKD - formerly called "CRF"): Chronic 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 causing or exacerbating feline kidney disease. And remember, cats are chronically dehydrated - especially CKD cats - when they are on a diet of predominantly dry food. The prescription dry 'renal diets' such as Hill's Prescription k/d - which are commonly prescribed by veterinarians - contain only a small amount of moisture (~10% versus 78% for canned food) 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 an extremely illogical and unhealthy practice 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 Hill's Prescription 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 a source of meat and the fourth ingredient is a by-product meal which is not necessarily an unhealthy source of protein but it would be nice to see some muscle meat ("chicken") in this product.
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 restricting protein to this level will prevent further deterioration of kidney function.
k/d restricts protein to the point that some cats - those that are not consuming enough of the diet to provide for their protein calorie needs - will catabolize (use for fuel) their own muscle mass which results in muscle wasting and weight loss. This internal breakdown of the cat’s own muscle mass will cause an increase in creatinine which needs to be cleared by the kidneys. The rise in creatinine, and muscle wasting, can lead to an often-erroneous conclusion that the patient’s CKD is worsening.
Of course, the same deterioration can occur in any cat that is not consuming enough protein, but 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. It is also water-depleted as is the very definition of all dry foods.
and it's nice to have some fresh new smarties to rotate the crop
