Help with a few things

My cat Tigger is nearly 18 years old and suffers from Kidney Disease and hypercalcemia. We have checked ionized calcium, which was high and PTH which was low. He also had an ultrasound performed by a specialist and no signs of cancer were found. So to explain the high calcium he either has idiopathic hypercalcemia (they don’t know why it is happening) or cancer which has not yet shown itself. Tigger is clinically ok but has lost weight.My biggest problem with him is that he doesn’t want to eat his cat food. He loves people food. He will not eat cat food but if I give him a jar of baby food or regular people food he gobbles it up. So he is hungry but just not willing to eat cat food. He cannot afford to lose any more weight as he is boney now. He is hungry because he will eat people food or baby food, just not cat food. I have tried every kind of cat food, have puried it, warmed it, etc….no go. My question is this: I know there are homemade diets that I can make but with both the kidney disease and the high calcium problem, I know I need to be careful. He could go on eating baby food forever but I know it is not balanced. We don’t seem to have a cat nutritionist in my area and I have looked on the internet for ideas but I really can’t find anything. I know it is better to have him eat baby food than to not eat at all, but everything I have read says baby food is not balanced enough. Any thoughts on what to feed this cat?Also, here are some of his blood work results:Ionized calcium: 1.80 Range: 1.16 – 1.34PTH: .50 Range: .40 – 2.50BUN: 27 Range: 20 – 30Calcium: 14.4 Range: 8.0 -11.8Creatinine: 2.9 Range: 0.3 – 2.1ALB: 4.2 Range: 2.2 – 4.4PHOS: 4.6 Range: 4.6 Range: 3.4 -8.5

My thought on this is, if he eats the baby food then keep feeding him that, but maybe add supplements to it? The kind you'd use if making raw/homemade diet. This could of course affect the flavour and put him off but I'd say it's worth a try. At 18 years old my inclination would be to feed him what he wants to eat and avoid the stress for both of you to try to introduce a new food.

I had a kidney failure cat and honestly towards the end, I fed her whatever she wanted to eat balanced or not.  You could try doing a phone consultation with Dr. Pierson about a recipe for your cat: http://www.catinfo.org/?link=makingcatfood#Note:  This website has some links for homemade diets for kidney failure cats:  http://www.felinecrf.org/which_foods.htm

You can add premixes using eggshell calcium (no phosphorus). Alnutrin is a very good and inexpensive option.

This information is based on humans:

A low-normal PTH and high calcium points toward some sort of auto immune problem. Unfortunately it can be quite difficult to track down, requiring lots of tests. High calcium due to cancer is rare and usually by the time high calcium shows up, you've already found out about the cancer because high calcium readings show up very late.