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Thread: Kidney function test, eGFR results of concern

  1. #1
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    Default Kidney function test, eGFR results of concern

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    I have less than 3 and a half years left until I have served my 22 year contract with the military. They have offered me a 5 year extension to this subject to being assessed medically fit.

    This would have been a simple consultation and a signing of my extension form, but unfortunately I had blood work carried out Feb 2020 for something unrelated and never followed up when some values were of concern.

    So they made me take a blood test again and the numbers are worse so now they have referred me to a renal specialist.

    When I was called in to discuss my results, I was expecting some liver and kidney markers to be high, having read some information on the forum.

    For liver, AST was 112 U/L and ALT was 396 U/L in Feb 2020 and for Apr 2021 ALT was 56 U/L with AST not on the results this time. So she was happy with the Liver results. There was some other ones a bit high, but she wasn’t concerned.

    For kidney, my creatinine was 116 umol/L in Feb 2020, and now its 144 umol/L. I told her about my creatine supplementation and heavy training and she accepted it would likely be that, but what her real concern was my “eGFR using creatinine (CKD-EPI) per 1.73 square meters” results.

    This was not on my list of things that I had researched on the forum. The Doctor said it was levels she’s expect to see in 70-80 year olds, not 37 year olds.

    In Feb 2020 it was 69 mL/min and in April 2021 it had worsened to 53 mL/min. The reference range is 90-200.

    Does anyone have experience with this particular metric and if it’s common amongst those who train with heavy weights?

    I’m waiting in the carpark until I can provide a urine sample as she said it something about comparing the blood and urine levels against each other.

  2. #2
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    Here's the equation: GFR (mL/min/1.73 m2) = 186 × (Pcr)-1.154× (Age)-0.203 × 0.742 (if female) × 1.210 (if African-American)

    You can also compare to one that uses bodyweight instead of an assumed surface area: GFR = {[140 - Age(yrs)] × Weight(kg)} / (72 × Pcr) × (0.85 if female)

    What's common to each one that your GP already dismissed? What does it correlate to?

  3. #3
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    Default Kidney function test, eGFR results of concern

    Quote Originally Posted by stef View Post
    Here's the equation: GFR (mL/min/1.73 m2) = 186 × (Pcr)-1.154× (Age)-0.203 × 0.742 (if female) × 1.210 (if African-American)

    You can also compare to one that uses bodyweight instead of an assumed surface area: GFR = {[140 - Age(yrs)] × Weight(kg)} / (72 × Pcr) × (0.85 if female)

    What's common to each one that your GP already dismissed? What does it correlate to?
    Okay, thanks stef.

    So, I think Pcr must be plasma creatinine? I see with these equations GFR is just inversely proportional to the creatinine and so since the latter is expected to be high, then the former will be expected to be low. Really estimating GFR this way is just Pcr expressed differently and with some assumptions that the older I get the worse my kidneys function . Weirdly, the heavier I get, the assumption is an improved GFR, when using the second equation.

    I found this calculator that uses the second equation: Creatinine Clearance (Cockcroft-Gault Equation) - MDCalc

    Putting my details in (BW =109 kg), my GFR would be 96 mL/min, so not low at all. But then there is some further adjustments for BMI, so after putting my height in (180 cm) it gives me a range of 66-78 mL/min.

    Aside form the fact that if an out of range PCr can be dismissed due to accepting supplementation and training being the cause, then so can GFR, it also seems like the age/weight/BMI adjustments may not be particularly accurate. Especially since the Doctor noted when recording my BMI today, that I am "highly muscular" and that I should not be considered as obese with my BMI of 34. Although, she might have just been flirting as she mentioned it again when checking my blood pressure with the "big cuff" and having to "manage with the extra details of my arm"- but probably not ha!

    Anyway, thanks very much for pointing out these equations. I could try ringing the med centre and convincing her that I'm actually okay, but since she already wants me to stop creatine supplementation for 1 month and get another blood test in addition to the referral to a kidney expert for scans etc. I don't think I'll have any luck. I'll jump through the hoops I need to to extend my career, but at least I'll sleep well without worry that I'm on my way to kidney disease . Thank you.

  4. #4
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    So first, with any test you need to know what it is actually testing and what it's limitations are. I'm not convinced that your doctor does.

    Serum creatinine is higher with more muscle mass, not just diet. Other things affect it too. But dammit, what kind of person says the level is okay because of your diet (noting the giant traps and thighs, but forgetting where the shit comes from in the first place and taking into account that a weightlifter is in the room), but then uses that same value to calculate another value and then start worrying? Complete logic fail here.

    You haven't had kidney function tested. You've had a blood value taken, one where any half-awake person or even minimally-programmed flow chart would expect to be higher than the couch-sitter reference range, come back "high." Now you've played around with equations, including one that takes into account weight and then corrects with BMI. It says "The Cockcroft-Gault Equation may be inaccurate depending on a patient's body weight and BMI" (note that this equation was developed for creatinine clearance and is being mashed into this use, so has some estimation deals to correct) Now what is BMI doing here? Are they using it to correct for weight where the weight is buckets of lard? You know, like you see with the non-training population. But that's not you. Your weight and BMI is high because of increased muscle mass. Neither formula (formulas they like since measuring 24hr urine is very exciting) takes into account muscle mass.

    Now this doctor with the analytical skills God gave a carrot wants to run an experiment on you, where you drop one variable that pushes up the magical blood test. Is there protein in your urine? Cystatin through the roof? I am assuming that you weren't showing dehydration on this blood test. Wait. Why am I doing this? Bad move, bad move.

  5. #5
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    Quote Originally Posted by stef View Post
    So first, with any test you need to know what it is actually testing and what it's limitations are. I'm not convinced that your doctor does.

    Serum creatinine is higher with more muscle mass, not just diet. Other things affect it too. But dammit, what kind of person says the level is okay because of your diet (noting the giant traps and thighs, but forgetting where the shit comes from in the first place and taking into account that a weightlifter is in the room), but then uses that same value to calculate another value and then start worrying? Complete logic fail here.

    You haven't had kidney function tested. You've had a blood value taken, one where any half-awake person or even minimally-programmed flow chart would expect to be higher than the couch-sitter reference range, come back "high." Now you've played around with equations, including one that takes into account weight and then corrects with BMI. It says "The Cockcroft-Gault Equation may be inaccurate depending on a patient's body weight and BMI" (note that this equation was developed for creatinine clearance and is being mashed into this use, so has some estimation deals to correct) Now what is BMI doing here? Are they using it to correct for weight where the weight is buckets of lard? You know, like you see with the non-training population. But that's not you. Your weight and BMI is high because of increased muscle mass. Neither formula (formulas they like since measuring 24hr urine is very exciting) takes into account muscle mass.

    Now this doctor with the analytical skills God gave a carrot wants to run an experiment on you, where you drop one variable that pushes up the magical blood test. Is there protein in your urine? Cystatin through the roof? I am assuming that you weren't showing dehydration on this blood test. Wait. Why am I doing this? Bad move, bad move.
    The more I’m mulling over what you’ve explained here, the more irritated I’m getting that the Navy is messing with my training again. Usually it’s fitness tests or some sort of compulsory circuit training initiative that winds me.

    I’m going to continue with my creatine supplementation, heavy training and high protein/calorie diet and accept that my blood test next month will show the same “concerning” values. I’ll take my chances that the renal specialist will do their check and assess my kidneys serviceable. Then I’ll get the GP to sign my form, hopefully.

    Again thanks for taking the time here, it’s very much appreciated.

  6. #6
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    It's a good practice to avoid commonly observed doctor limitations by getting tests as far out from heavy sessions as possible, dropping supplements a few days out, and going in hydrated.

    Stupid to have to do this, but it's an artifact of a diseased system.

  7. #7
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    As is common the person charged with interpreting the labs doesn't understand what they mean.

    I'm a medical doctor. One thing your doctor overlooked is the "e" in eGFR. It stands for estimated. As in they don't have any idea what is your actual glomerular filtration rate, but the computer knows that fat, diabetic, hypertensive, out-of-shape humans with those values might have one in the range of what is reported for you if they had early kidney disease. eGFR is nothing more than a red flag to catch the attention of people who don't know what the creatinine value means. Then - notice it's adjusted for race? As though every white person has the same biochemistry as every other white person, and every black person has the same biochemistry as every other black person, and they're always different?

    It isn't hard to measure glomerular filtration rate. It takes time, injecting you with a non-metabolized chemical called inulin, and measuring your pee for a while. Somebody has to risk getting your pee on their hands when they open the jug. This is too much work for the lazy medical system, primarily concerned with getting more money for less work. I would venture if they actually measured your GFR it would be normal, since you're healthy. The commonest things causing early renal failure in your age group are high blood pressure; meth or cocaine use; kidney diseases you were born with; diabetes; and overuse of non-steroidal antiinflammatory agents like ibuprofen and naproxyn. Absent one of those I think the chance of you having kidney disease is close to zero.

    But logic may not prevail. You could ask for a real GFR measurement, rather than allowing your future to be decided by a guess.

    Otherwise, time to look at reality as you try to adjust to an insane world: Is it more important to you to take creatine for a month, or to stay in the Navy?

    And you've learned a valuable lesson about medical testing, and medicine in general: Nobody cares but you. Follow up, follow up, follow up right away. Call them. Bug them until you get an answer. You might have been able to head this off in February.

    Whenever they're doing kidney tests, drink so much water you have to stop and pee on the way to the lab. Make sure your pee is colorless. Don't put tap water in your pee collection cup. They few bright ones figure that out.

  8. #8
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    Quote Originally Posted by Leo M View Post
    As is common the person charged with interpreting the labs doesn't understand what they mean.

    I'm a medical doctor. One thing your doctor overlooked is the "e" in eGFR. It stands for estimated. As in they don't have any idea what is your actual glomerular filtration rate, but the computer knows that fat, diabetic, hypertensive, out-of-shape humans with those values might have one in the range of what is reported for you if they had early kidney disease. eGFR is nothing more than a red flag to catch the attention of people who don't know what the creatinine value means. Then - notice it's adjusted for race? As though every white person has the same biochemistry as every other white person, and every black person has the same biochemistry as every other black person, and they're always different?

    It isn't hard to measure glomerular filtration rate. It takes time, injecting you with a non-metabolized chemical called inulin, and measuring your pee for a while. Somebody has to risk getting your pee on their hands when they open the jug. This is too much work for the lazy medical system, primarily concerned with getting more money for less work. I would venture if they actually measured your GFR it would be normal, since you're healthy. The commonest things causing early renal failure in your age group are high blood pressure; meth or cocaine use; kidney diseases you were born with; diabetes; and overuse of non-steroidal antiinflammatory agents like ibuprofen and naproxyn. Absent one of those I think the chance of you having kidney disease is close to zero.

    But logic may not prevail. You could ask for a real GFR measurement, rather than allowing your future to be decided by a guess.

    Otherwise, time to look at reality as you try to adjust to an insane world: Is it more important to you to take creatine for a month, or to stay in the Navy?

    And you've learned a valuable lesson about medical testing, and medicine in general: Nobody cares but you. Follow up, follow up, follow up right away. Call them. Bug them until you get an answer. You might have been able to head this off in February.

    Whenever they're doing kidney tests, drink so much water you have to stop and pee on the way to the lab. Make sure your pee is colorless. Don't put tap water in your pee collection cup. They few bright ones figure that out.
    The only thing in the list that applies is high blood pressure. Every male on my paternal side has high blood pressure. Granda is in 87, still up a ladder with a paint brush, so I’m not concerned about it. I don’t take cocaine or meth, nor even caffein. I’m presuming I’d know it if I already had kidney diseases born with, so I’m probably fine.

    I did mention to the GP that I’m terrible at keeping myself hydrated- I just don’t realise I’m thirsty for hours, then end up gulping down a couple pints of water in one go. She wrote all this down, so the kidney doctor at the hospital should pick up on it.

    I’ll keep the advice about drinking a lot of water for urine tests in mind in case that’s something they want to be checking.

    I gave one yesterday, for them to check some sort of ratio involving creatinine. Sat in the car drinking water until I needed to go because I had driven to the doc’s straight after getting up and showered. It was neither dark nor colourless.

  9. #9
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    Leo and Stef nailed it already, I just want to say that I went through the same shit. The funny thing was, the kidney specialist I was referred to took one look at me and said "You're kidneys are fine". He explained to me why my creatinine was high and I told him I knew that, we chatted a bit. Cool guy, though no lifter. Then he proceeded to do his routine, sonography, lab tests, thorough physical exam. Good doctor.
    I think you're spot on with your approach, Sea Hawk, and hope the doctor you'll see for your kidney problems will be as cool and knowledgable.

  10. #10
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    I think I've told this story before, but my (former) primary care doc flipped out when my creatinine was .02 outside the reference range, despite me reporting my exercise habits and creatine supplementation. I ended up talking to his PA to follow up, as he was on vacation, and asked her, "You are familiar with the effects of muscle breakdown and dietary creatine on serum creatinine, right?" "....um, yes."

    It's unfortunate that your career depends on a doc's ability to pull their head out of their ass, but here we are.

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