Guest guest Posted October 20, 2003 Report Share Posted October 20, 2003 Everyone has creatinine in their blood. Creatinine is the breakdown product of the natural creatine in our muscles, basically. It occurs naturally as you use your muscles. The only difference in people with chronic renal insufficiency is that the kidneys don't eliminate as fast, and it builds up to a higher level. The higher level of creatinine itself isn't really bad. Rather, it's a convenient indicator of kidney function. GFR means glomerular filtration rate. Since the glomeruli are the filters in the kidneys, and the part that is primarily affected by kidney disease, GFR measures the function of the glomeruli. Now, while it's possible to actually measure GFR by injecting a radio isotope and then measuring how much is cleared in a given time, very few of us have actually ever had that done. What they do instead is they either use a calculation based on serum creatinine, weight, and various other factors (there are various equations that can be used), or, they use your own creatinine as a substitute for the radio isotope. This is what they do when they analyse your 24hour urine collection - measuring how much creatinine passed through into the urine over a 24 hour period. This gives your " creatinine clearance " , which is more or less synonymous with GFR. It's not that simple though, in that creatinine clearance only really estimated the GFR. This is because up to about 10% of creatinine is not cleared by the glomeruli, but rather by the renal tubules. The renal tubules may not be as affected by your kidney disease as the glomeruli are, and so, creatinine clearance may overestimate GFR(or % kidney function) by a certain amount. Usually, the inaccuracy isn't important when you still have a lot of kidney function (and 50% falls into that category). But when you get closer to needing dialysis, like say, approaching or under 20% kidney function (which is the same thing as saying that GFR is 20%), then the overestimation of GFR by creatinine clearance (24 hour urine collection) becomes greater, and then a calculated GFR based on serum creatinine is more accurate. But nothing is absolutely accurate except that test that measures the clearance of a radio isotope. However, close enough is good enough in this case - which is why few people actually get their GFR actually measured that way. Nowadays, people tend to get diagnosed earlier, but quite often, there is nothing to diagnose until you're already down to 50% kidney function. Earlier than that and it just doesn't show up in the blood work. This is because we all start out with more than 100% kidney function, and it takes significant loss of function until it shows up in the blood work. Hope that helps. Pierre GFR > I feel like I need " Kidney Biochemistry 101 " . I understand that creatinine in the blood and protein in the urine are indicators of renal dysfunction. What are the indicators for the GFR. Is it one definitive test or a calculation derived from other lab results? Also, the GFR = the % of kidney function left? Always having been very healthy I am having a hard time with this diagnosis: 50% kidney function. I knew I was constantly bone tired but this is a shock. Thanks Pierre and for your info. > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted October 21, 2003 Report Share Posted October 21, 2003 Pierre, Thank you for explaining that so well...I can now cross one of the questions for my doctor off my list. I'd also like to say a big thanks to all those who set up the web site in such an easy to read layout. My mother has had visible blood in her urine for over 2 years and has high blood pressure...but is one of those people who refuses to see a doctor for further testing. After finding out my diagnosis and READING your website she is finally going in to have things checked, I'll let you know what her results are. Thanks again! Amy GFR > I feel like I need " Kidney Biochemistry 101 " . I understand that creatinine in the blood and protein in the urine are indicators of renal dysfunction. What are the indicators for the GFR. Is it one definitive test or a calculation derived from other lab results? Also, the GFR = the % of kidney function left? Always having been very healthy I am having a hard time with this diagnosis: 50% kidney function. I knew I was constantly bone tired but this is a shock. Thanks Pierre and for your info. > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted October 21, 2003 Report Share Posted October 21, 2003 Thanks Amy. I tried to make the site as simple as possible, with easy and logical navigation, and without any gimmicks. If it helps in convincing even one person like your mother to see a doctor, then it was worth it. If she needs any more convincing, just the fact that a great number of people who are on dialysis are there not because they had a kidney disease like IgAN, but simply because of hypertension. High blood pressure by itself is a killer, and not just with regard to the kidneys. I will be interested in hearing how it comes out. Good luck to her. Pierre P.S. My mother is the same when it comes to seeing a doctor. GFR > > > > I feel like I need " Kidney Biochemistry 101 " . I understand that > creatinine in the blood and protein in the urine are indicators of renal > dysfunction. What are the indicators for the GFR. Is it one definitive > test or a calculation derived from other lab results? Also, the GFR = the % > of kidney function left? Always having been very healthy I am having a hard > time with this diagnosis: 50% kidney function. I knew I was constantly > bone tired but this is a shock. Thanks Pierre and for your info. > > > > > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted February 10, 2004 Report Share Posted February 10, 2004 Hi . It means glomerular filtration rate, and it's the equivalent of saying you have 40% kidney function (where 10% is normally time to start dialysis). Now, there are various different ways of estimating GFR, different formulae can be used to calculate it. Just guessing from your serum creatinine, it's probably not far off, as that levels of serum creatinine for the average person would typically be equivalent to somewhere around 50%. Calculated GFR can vary a little from one time to the next, as can serum creatinine. Pierre GFR > Hello everyone, > > I recently received some results from my Nephrologist. He says my serum creatinine is stable at 151 umols/l and I have a calculted GFR of 40 mls/minute. He explained the significance of the 1st result but told me that only a G.P. would understand the GFR. Does anyone know what GFR is? > > Thanks, > > (London U.K.) > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted February 10, 2004 Report Share Posted February 10, 2004 Hi . It means glomerular filtration rate, and it's the equivalent of saying you have 40% kidney function (where 10% is normally time to start dialysis). Now, there are various different ways of estimating GFR, different formulae can be used to calculate it. Just guessing from your serum creatinine, it's probably not far off, as that levels of serum creatinine for the average person would typically be equivalent to somewhere around 50%. Calculated GFR can vary a little from one time to the next, as can serum creatinine. Pierre GFR > Hello everyone, > > I recently received some results from my Nephrologist. He says my serum creatinine is stable at 151 umols/l and I have a calculted GFR of 40 mls/minute. He explained the significance of the 1st result but told me that only a G.P. would understand the GFR. Does anyone know what GFR is? > > Thanks, > > (London U.K.) > Quote Link to comment Share on other sites More sharing options...
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