This is what I know...kidneys are responsible for removing excess potassium from the blood. Diseased kidneys will not be able to do that well, which results in too much potassium in the blood. Our hearts are regulated by potassium, along with other things. So, I am sure they checked her levels and found them too high, which could potentially cause heart and other nervous system issues.
I've been interested in this subject as well, though I haven't really been able to find any information as to wether 801010 is good for someone with kidney disease or not. My Dad also has kidney disease, and he too takes potassium blockers. The really irritating part is they tell him to eat lots and lots of meat, which is of course a big contributer of kidney disease in the first place. (at least they did while he was on peritoneal, I'm not sure if they still recommend it since he's switched to hemo)
I'm very sorry about your Mom and your Uncles; I know it's tough because I've seen my Dad deal with it for five years now.
ONe of the reasons why you would want to eat a fruit diet is that it is low in phosphorous. Chronic Kidney Disease has trouble with phosphorous and doctors recommend 800-1,000 milligrams of phosphorous daily as the max intake.
Grains are very high in phosphorous at least around 1 mg P for every calorie (if it is a whole grain) so you can imagine if a 2,000 calorie diet is grain based there will be too much phosphorous.
Dairy is high too. Just one cup of skim milk has 250 mg P.
The excess potassium may be a problem even from fruits, in my estimate. Fortunately, there are certain fruits that contain less potassium as well.
Here's the other part though, kidney disease tends to come from diabetes. So if you can reverse the diabetes you may be able to reverse the kidney disease too.
If you want to help out your loved one perhaps you can take cronometer and input their diets and show them other options and show how they can meet their requirements a lot better.