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    Michael L. Aaronson, MD
    Kidney Doctor and High Blood Pressure Specialist
    7401 O Street Lincoln, NE 68510
    Phone: 402-484-5600

    Friday, March 8, 2019

    What is the Risk of My Kidneys Failing Over the Next 5 Years? Should I be Concerned?

    The Kidney Failure Risk Equation 4 Variables
    Case presentation: A 68 year old male patient with chronic kidney disease stage 3 from diabetes mellitus type 2 presents to his primary care provider for a routine evaluation. His blood pressure is stable and controlled at 129/75. He has 345 milligrams of protein in his urine. He is on the ace inhibitor lisinopril to treat his high blood pressure. This gentleman lives in North America. The patient has a glomerular filtration rate of 42 (42 per cent of the patient's kidney function remains intact), so he has CKD 3 as stated above. Note: we consider starting people on kidney dialysis when they have 5 to 15 percent of their function remaining. So it appears that the patient has lots of time before he will need to start kidney dialysis because he needs to lose 38 percent of his function before he will be placed on renal replacement therapy. No worries, right? Or should we worry?

    The patient's primary doctor suggests this man go to the kidney specialist to get evaluated for his chronic kidney disease (CKD) and discuss strategies for prevention of worsening function. Is this a good idea?

    The answer to the question asked is "yes." This gentleman has a 5.47 percent risk of progressing to kidney failure over the next 2 years and a 16.1 percent risk of renal failure over the next 5 years using the kidney failure risk equation.

    The four variables used to calculate the patient's risk are:
    1. Is the person male or female?
    2. What is the age of the patient?
      1. How old you are.
    3. What is the Estimated GFR (glomerular filtration rate)?
      1. The percent kidney function you have remaining.
    4. What is the Urine albumin to creatinine ratio?
      1. The amount of protein present in the urine.
    The formula also takes into account whether or not a patient lives in North America or not, because this apparently makes a difference.

    Let's show this information again graphically. Plug the data into the formula from the clinical vignette as shown in the figure below (note: links to allow you to do this in real time are provided later on in this medical blog):

    After performing the calculation we find out that:

    Over the next two years, the risk for progression is:
    • 5.47%
    Over the next 5 years, the risk for progression is:
    • 16.1%
    Which of the 2 numbers is more important? If you have Stage 3 chronic kidney disease, consider using the 5 year data set and the following:
    • 0-5% risk of progression is low risk, 
    • 5-15% is an intermediate risk, 
    • and more than 15% is high risk.
    This patient is at high risk for progression to end-stage kidney disease. Please note that the predicted risk can differ from the actual observed risk. Full disclosure: I'm a nephrologist. I believe that kidney doctors make a difference. I would opine that under the guidance of a kidney doctor, working closely with the patient's primary provider, the patient's actual progression to end stage kidney disease will be delayed. You are better off with the assistance of a nephrologist. Nephrologists have skills and knowledge in this area.

    Sidebar: kidney failure prevention happens to be one of my areas of expertise. My passion is prevention -- keeping you off the kidney dialysis machine through risk stratification which includes blood pressure management, electrolyte management, and more.

    Doctor Michael Aaronson: How do I calculate the risk of my kidneys failing over the next 2 to 5 years? There are a few ways to do it. One way is to calculate the 4 variable kidney risk equation with your laboratory data. Or you might try the 8 variable kidney risk equation with your laboratory information that adds serum calcium, phosphorus, bicarbonate, and albumin (the amount of protein in your blood) to the mix. If you are having trouble, no worries! We can calculate the risk for you.

    To the primary providers out there reading this medical blog, I would suggest not using this tool as your sole reason to refer (or not to refer) to a kidney specialist. The prediction model is not perfect. There are many other indications for referring a patient to a kidney specialist such as polycystic kidney disease, work up of kidney stones, and hypertension control.

    To the patients who have been referred to see a kidney specialist I would suggest the following: If your primary makes the suggestion that you see a kidney doc, please do so. Actually follow through with it.

    Different primary providers have different cutoffs for determining when it is time for a patient to see a nephrologist. Some people think a 10 percent chance of kidney failure justifies a referral. Some general practitioners have a higher threshold to refer. Others have a lower threshold. The timing of referral should take into account all of the factors involved, not just one equation. If you decide to see a kidney specialist, we are here for you.