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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

    Saturday, February 9, 2019

    How Severe Is My Chronic Kidney Disease?

    Nephrologists use formulas to determine whether or not you have chronic kidney disease (CKD). The following pieces of information are plugged into a formula to determine your stage:

    1. How old you are
    2  Whether you are male or female
    3. Your race (black or white)
    4. Your gender (female or male)
    5. The result of certain blood tests, usually the creatinine.

    If the number turns out to be less than 60 for 3 months or more, you are likely to have chronic kidney disease or CKD.

    Kidney doctors also consider the amount of protein present in the urine when determining whether or not CKD is present. If you have more than 30 mg/g present in a urine sample for more than 3 months you may have CKD.

    These tests are not perfect and there can be errors inherent in the assay. So when the value in a particular patient is close to 60, and there is no explanation for the presence of chronic kidney disease, a test called cystatin C can be helpful to the nephrologist to figure things out. There is usually more to the story than just the number, but accurate information helps our assessment.

    Here is an example: A 62 year old white male with no medical problems and a serum creatinine of 1.3 mg/dl who is muscular has a CKD-EPI creatinine equation that calculates to 58 ml/min/1.73m2. In other words, this 62 year old has around 58 percent kidney function remaining. To put this into perspective, we perform kidney dialysis at 5-10 percent function remaining. Using our standard formulas, this person has CKD 3. Or does he?

    Creatinine comes from muscle. Muscular people generate more creatinine than non-muscular humans. In these patients, the creatinine can be "artificially" high and make it seem like there is chronic kidney disease when there actually is no problem present.

    This clinical vignette is the perfect scenario to order a cystatin C. This patient may or may not have a kidney problem. Muscular humans can have chronic kidney disease. And if they do, they need a thorough evaluation and possible treatment.  If he has chronic kidney disease we need to follow him closely to try to avoid the progression to CKD 5, the last stage prior to needing dialysis. If he doesn't have CKD, we can avoid costly tests and medical bills.

    The patient had a cystatin C value of 0.7 mg/L. Plugging this value into the CKD-EPI creatinine-cystatin equation gives the patient a GFR of 83 ml/min/1.73m2. In other words, he has 83% function remaining - not 58 - and has CKD 2. The patient is in the green, not the yellow (see figure above). Or is he?

    We need an assessment of the amount of protein in the urine. We need to assess the patient for their albumin to creatinine, ACR category. If the patient was spilling more than 300 mg/g of protein in the urine, the risk of progression of chronic kidney disease would be very high. The patient would be in the orange category (see the figure above). In this setting, the patient's CKD would be considered more severe than a patient without so much protein spillage. He would have increased risk for progression to kidney failure and end stage renal disease. Moreover, the recommended frequency of monitoring would be more frequent, and a referral to a nephrologist would be recommended.

    It turned out that this patient was taking non-steroidals, NSAIDS, for pain related to heavy workouts. He was spilling a significant amount of protein in the urine. The ibuprofen was the culprit associated with the CKD and the protein in the urine. The patient stopped the NSAID and follow up was scheduled to monitor for progression of CKD.

    In sum, accurate assessment of your kidney function is important. We want to know how severe the chronic kidney disease is. Although we want to know the stage of CKD you are in, it is also important to monitor trends over time. The goal is to keep you off the dialysis machine and keep the kidney function stable.