dr falkinburgh,i am 80 year old man with moderate kidney impairment.last gfr was 49,and no protein in recent microalbumin test.i take 2 8oz glasses of prune juice 2 times a week for constipation.each glass of prune juice has 430mg of potassium.would this not aggreviate my kidneys or am I better off with 5 dried prunes 290mg potassium.are there safer products for people with impaired kidney and constipation.appreciate your answer

Good morning, Howard,

Potassium (K), per se, is neither good nor bad for the kidney.  If kidney failure progresses to the point that the kidney is unable to excrete the normal dietary potassium load (which is extremely variable) the level of K in the body rises.  If that level reaches toxic concentrations, the skeletal aand cardiac muscles are effected and they become very weak.  The most profound final effect is cardiac arrest and death. Therefore, we worry about the level of K in the blood rather than the amount of K in the diet.  High levels of K in the blood can be treated by dietary K restriction and certain medications.

In your specific case, the real queston is whether or not your blood K level is elevated when you consume your usual diet (which included 860 mg of K containing prune juice). If it is elevated (which I, intuitively, doubt), I would restrict your dietary K as a first step.  If your levels are normal (which I suspect is the case) I would continue your present diet unless or until some other circumstances come to pass.

Another question that you did not ask but that is very pertinent, is why do you have kidney failure?  There are many causes of kidney failure.  Some are progressive, some are not.  Some have treatments that need to be prescribed, others do not. As a minimum you need to have (if you have not had already) a renal untrasound to determine the size of your kidneys.  small kidneys suggest a chronic disease which, likely, does not lend itself to treatment.  But, large kidneys, on the other hand, suggest a more acute process which may be due to a disease which has a treatment. An ultrasound also will rule out any obstructon to the flow of urine from the kindey to the bladder. You also need to have your urinary protein excretion documented, as different quantities of protein excretion are associated with different diseases. There are a variety of additional, simple tests that will help delineate the nature of your kidney disease.

At age 80, it is very possible that you simply have hardening of the arteries of the kidney. If you, so might benefit from long term "statin" therapy.

So, you need a complete nephrology evaluation and if your primary care doctor is uncomfortable doing this, I would be quick to consult a nephrologist.  For him, this is a typical day at the office.

Hope this is of some use to you.

Please feel free to follow up if anything is unclear.

Best of luck to you.


Dr Falkinburg


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Newell R. Falkinburg, M.D. FACP


Any question regarding hypertension or clinical nephrology


35 years of experience in the field of nephrology & hypertension. Emeritus Professor of clinical Medicine at a major medical school and director of Nephrology & Hypertension at a university affiliated medical center.

M.D. Board certified internal medicine Board certified Nephrology & hypertension

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Fellow, American College of Physicians

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