Poor kidney function and diet

Factual Questions
1

I have a story idea (hey, we ARE coming up on National Novel Writing Month a.k.a. NaNoWriMo) but I need some help from the medical sorts on the Dope.

One of the characters in the past suffered a Horrible Accident. Among other side effects, said person had reduced kidney function. This is not due to disease but rather because the Horrible Accident destroyed a significant amount/most of said characters’ kidneys. So what’s left of his kidneys are presumably not deteriorating in any way. Fortunately, this person lives in the future where medical care is even better than today and so most/all problems with such reduction in kidney function is easily and routinely handled EXCEPT –

This character (as part of the story) finds himself in, basically, a rural/quasi-wilderness situation for an extended period of time. No advanced medical care! No dialysis. No advanced medications. Oops.

Now, assuming this person doesn’t require dialysis to live and he’s smart/educated enough to do the right thing (he’s a smart guy, trust me - I’m the author)…

  1. About how much of a person’s kidney function can be lost before symptoms show?

  2. How much is enough kidney to get buy/survive with symptoms but without needing dialysis?

  3. I’ll take it as a given that such a person will have to be very careful about salt intake, not overdoing fluids, etc. as even if his remaining kidney bits are functioning properly there will be a problem of capacity - 1/2 of a kidney, no matter how healthy, (as an example) is just not going to have the filtering capacity of 2 healthy, whole kidneys. - What else will this person have to limit the intake of?

  4. I’m assuming a careful diet will do much to mitigate the problems, even if it doesn’t solve all of them. Assume this person will have access to good, healthy food. What does he need to avoid? What does he need to eat? What would an optimum diet for such a person look like?

  5. What symptoms might he experience if he gets slack in his habits, or is stuck in a situation where he can’t get an ideal diet?

Yes, a part of the story involves the problem of someone whom an advanced technology can keep healthy, but who is at a severe disadvantage in the “wild”, but not to the point he’s going to keel over dead in a month or whatever.

2

This is relevant as a part of what you’re looking for.

I am diabetic, and every 3 months my blood and urine are tested for various factors. In general my kidneys are ok, but if I’ve been on a low-carb (high protein) diet, it starts to affect my kidneys. Supposedly the protein molecules are large, and the kidneys become partially clogged. So your character would want to be on a diet of high carb to protein ratio.

3

First thing you need to realize is that the Kidneys don’t just filter the waste in the blood. There are many different bodily functions that are regulated through the kidney. The kidney has a role in regulating blood pressure, blood volume, blood pH, glucose production, production of red blood cells, vitamin D synthesis, just to name a few. These are important functions functions, that can have wide effects throughout the body.

Now, as for the actual filtration of the blood. The capacity of the kidneys is measure in the Glomerular filtration rate, or GFR, the GFR is normally estimated by estimating the Creatine Clearance, or CrCl. Normal CrCl is 120mL per a minute. I’m going to base the answers to my questions on someone that is on no other drugs, since someone with impaired clearance that is still high enough to avoid symptoms can still have accumulation in renally eliminated drugs. I know you said he was healthy, and I doubt your character is on other drugs, but I’m almost a pharmacist. When I look at renal function drugs are my first thought!

Now, let me see if I can answer your questions one at at time.

Renal damage is put into 5 stages, symptoms start to show up in stage 3, with a CrCl 30-59, with calcium absorption abnormalities, malnutrition, and anemia. Things start to get serious at stage 4 CrCl 15-29 with levels of phosphate and potassium starting to build up in the blood. The worst is stage 5, also known as End Stage Renal Failure, with a CrCl <15. This is where people pretty much stop urinating, and require regular dialysis.

So, to answer in one sentence, when you have 25% of capacity remaining (CrCl<30) is when physical symptoms really start showing up. You can lose 75% before someone notices enough to go to a doctor.

Sorta answered in the last question, dialysis is required in end stage renal failure when CrCl <15, or with about 10% of kidney function remaining.

A person with failing kidneys needs to limit the amount of Phosphorous, Potassium, Protein, Magnesium, and Chloride. They also need to increase the amount of Calcium they eat.

There are whole cookbooks to answer this. I have some handouts that list all the major food, but I’ve spent enough time posting this already, don’t want to go look for them. If no one else answers, and you need it, I’ll take the time to find those handouts.

Edema, uremic symptoms (cold intolerance, SOB, fatigue), palpitations, cramping, muscle pain, depression, anxiety, sexual dysfunction, pruritus (itching), and severe weight gain. At least, these are the major ones.
I hope this helps!

4

So, assuming our hero is out in the woods and away from whatever medical care is maintaining his normal health, over a relatively short period of time (however long it takes for prior treatments to wear off or whatever) will his blood pressure go up? (I’m assuming up because with impaired kidneys he’ll retain fluid.) Will his blood volume go up, even as a lack of erythropoeitin reduces the number of red blood cells (over several weeks, correct?) which leads to anemia and the symptoms of anemia like shortness of breath and fatigue? Vitamin D problems could, over the long haul, lead to weakened bones, of course.

Would blood pH tend to go up or down? Is that treatable by diet? Or does it require some sort of injection?

What is the effect on glucose production, up or down?

So, assuming his condition is stable - that is, he has reduced kidney tissue but no underlying disease process or deterioration - he could, if he’s careful, continue for a long time with symptoms that are between mildly troublesome to fairly annoying but not getting worse? He wouldn’t feel great but would be able to function?

I think it does.

Our hero would have issues with swelling - I’m assuming this is most likely to show up in hands, lower legs, face, etc? He’d feel tired and cold a lot/most of the time, and get winded easily. Heart palpitations during just exertion or during rest as well? Muscle cramps, aches and pains… would have trouble remaining upbeat, would be anxious (when it comes to his health perhaps with some reason), sexual problems, and would itch frequently. Is the weight gain usually fluid retention? Or something else?

So… he should stick to complex carbs in his diet, be careful which vegetables and fruits he eats (some OK, some not - if you have to minimize potassium, for instance, you might need to avoid bananas, right?), and stick to just enough protein to maintain his muscle mass and no extra, right? Low protein by our standards.

Let’s say he has 15-20% kidney function. What kidney he has is normal and healthy, but he just doesn’t have that much. If he’s careful about his diet/fluid intakes he’ll have minimal symptoms, right? But if he screws up he’ll start showing more symptoms, right? Then, if he goes back to being a good boy I’m assuming the symptoms will subside back to a lower level, correct? After awhile, of course, as his kidneys would have to “catch up” with filtering duties. But a better diet won’t necessarily help with anemia in this case, so no matter what he’ll probably still fatigue easily.

Am I understanding things correctly here?

5

Wow - lots of views, few replies.

Well, here’s a bump just to see if any other medical types want to contribute.