Gump also has kidney disease and probably has about 30% kidney function or less (he'll be 18 in a week and he's hanging in there pretty well...knock paws on wood). It used to be more commonly called 'kidney failure', but now it's also called kidney disease as some cats can live for years with reduced kidney function with supportive treatment (sq fluids, diet, other supplements, and frequent monitoring and bloodwork). But ECID (every cat is different) and the disease is generally progressive. You probably already know all that, but just wanted to mention it. 30% or less kidney function sounds bad, but someone recently mentioned that some people live their whole lives with only one kidney.
I am more concerned about the phosphorus content of the food than the amount of protein. Actually restricting protein too much can be detrimental - protein is needed for cellular repair and energy, etc. I recently read an article by a well respected vet who says that older cats protein requirements increase as they age. The protein thing is a debatable topic, and some still focus on protein, but the phosphorus content isn't controversial and feeding lower phosphorus food is beneficial. I focus more on finding foods with lower phosphourus (meat does contain phosphorus and you need to find out the levels of different canned foods) and lower sodium. I wouldn't want to feed super high protein, but some good quality protein is essential. The list at felinecrf.org (
http://www.felinecrf.org/canned_food_usa.htm) is pretty comprehensive and shows levels of phosphorus, sodium, protein etc of different foods. There are some better quality 'non rx' canned foods that also fit the bill and may have better quality protein with lower phosphorus content. Organix, some of the Merrick varieties and some of the Evo 95% come to mind and are pretty good.
If your friend wants to feed a 'kidney diet' and is concerned about the cost, there is one called Hi-Tor Neo which is less expensive, but you usually have to order it online because it's not found often in vet offices and other stores.
Good info also at felineoutreach.org, Lynette Ackman's blog, and the feline crf sites are also good and discuss the benefits of restricted protein and rx diets.(felinecrf.org and felinecrf.com)
Here's a quote from an informative CRF article at holisticat.com (
http://www.holisticat.com/crf.html):
..."In the past, it was believed that a low protein diet was essential in controlling CRF. The idea behind this was to supposedly cut down on the kidneys' load. However, studies done on dogs in renal failure, show that a low protein diet did not help said dogs. Since cats have an even higher protein requirement than dogs, it seems unlikely that they could thrive (or even properly exist) on low protein diets.
As an obligate carnivore, they need the nutrients only available from meat. My personal (and I like to think, informed) opinion is that cats with CRF should eat the same food that other healthy cats eat. Please check the references especially 9 and 10 for more arguments for feeding CRF cats a diet high in protein.
Cats are unique when it comes to diet. In all cats, their high protein requirement is due to high activity of hepatic enzymes which are responsible for ureagenesis i.e. the conversion of ammonia to urea in the liver. Cats do not have the ability to decrease the activity of these hepatic enzymes.
So it is dangerous to feed them a low protein diet as their bodies break down proteins via through the urea cycle on a continual basis regardless of the amount of protein fed. If cats do not get protein from diet, they will suffer from muscle wasting as their bodies will literally try to utilize protein internally.
Please do not deprive your cat of valuable protein (from real meat)! That said, only in very late stages of kidney failure, one can consider this purely for palliative relief from symptoms of uremia and azotemia.
There are several mouse studies all of which have found a positive relationship between protein and amount of "erythropoietic units" in spleen cells. Cats on a raw diet (at least 95% meat, including organs and bones) do not typically develop the muscle wasting or anemia commonly seen in cats with CRF because adequate protein amounts provide their body's basic building block not the least of which is RBC production.
The bottom line is that protein must come from an animal source, and must be of highest quality i.e. not primarily beaks, feathers, fur, claws, etc, just what comes with a whole bird/animal. The food should be digestible i.e. utilized by the cat's body so the kidneys do not have to process colors and preservatives such as dyes, BHA, BHT, etc...."
I have also found that slippery elm bark (herb) is an alternative to pepcid-ac for helping with nausea and excess stomach acid. I mix it with water and syringe it. You can try to mix it in the food, but Gump seems to be bothered by the taste. It's a powder that you can find in some health stores (I found it at Whole Foods) and online. SEB is also recommended by some more conventional sites like felinecrf.org.