Feeding dry foods is what causes creatine levels to be higher then normal unless there is a tumor or a deformity of the kidneys.
Dry foods no matter what kind it is will dehydrate the kidneys causing the cat or dog to drink more water. This makes the kidneys work really hard by dehydrating them and hydrating them. This ongoing off and on will wear the kidneys out faster than old age will do. Think of your heart organ working all the time if you were to run every day and never stop. Your heart would be stressed from this right? Well so will the kidneys or any other organ that works more than it should.
As for the higher kidneys levels in blood work when fed a raw diet; only the BUN level can be slightly higher because this stands for the protein in the diet which a raw diet is a higher quality protein then processed foods are. On the other hand, the higher levels of the creatine are sign of damage to the kidneys, BUT dehydrated kidneys will show signs of damage causing the creatine levels to be high and can be corrected once you stop the dry foods entirely.
Cats are literally not designed to eat anything but raw. All their organs and digestive system runs smoothly on raw and all processed foods that are cooked are alkaline. Raw keeps the cat’s system acidic so that his body thrives and functions purrfectly…
Alkaline diets (AKA all commercially processed COOKED foods) disturb a felines digestive and urinary balance. A homemade raw meat cat food diet will help to maintain the pH acidic environment necessary for their digestion and absorption of calcium. The acidic environment stimulates the pancreas to reduce digestive enzymes; this maintains pancreatic health and prevents atrophy of this important organ and others. The strong digestive secretions allow very few parasites to get past the stomach.
It is important to note that commercial pet foods, which are cereal-based or not, do not nurture a naturally pH acidic stomach environment like a raw meat diet for cats; because of this, Feline Diabetes, Feline Urinary problems (FUS) and Feline Irritable Bowel Disease (IBD) and early kidney disease normally disappear when fed a raw meat diet. Alkaline diets disturb a felines digestive and urinary balance.
I hope this was helpful 
Felice Arata
