Talk:Assessment of kidney function/Archive 1

Archive 1

CKD 1 through 5?

Shouldn't there be a discussion of the Chronic Kidney disease stages 1 through 5 as they rate to GFR or eGFR? [1] BillpSea 05:43, 30 September 2007 (UTC) glomerular filtration is NOT fluid filtered from kidney, I actually don't think there is any fluid that filters from kidney unless you wanna consider urethral discharge as filtered. If I understand correctly GFR is the rate at which fluid that entered kidney through afferent artery gets filtered through fenestrated membrane from bowman's capsule reaching glomerular capillary before exiting from efferent arterioles. I think my language is little clanky but I think (I hope I think) I have described GFR very accurately. —Preceding unsigned comment added by Ninad 1999 (talk • contribs) 02:50, 3 March 2010 (UTC)

Corrected C-Cr equation wrong?

Surely 1.73 should be on the bottom of the equation, and the patients actual BSA at the top. That way for larger patients, the observed value will be adjusted upwards not downwards. — Preceding unsigned comment added by 202.59.16.106 (talk) 06:33, 11 September 2012 (UTC) See the next paragraph. -- Dr. Hartwig Raeder (talk) 14:06, 12 November 2012 (UTC) You will not find my formula GFR(1.73 m²/BSA) in any of the textbooks. You will need this formula for classification (stadium 1 to 5 of chronic renal failure, ICD-10 N18.1-5). To antinormalize you have to write GFR(1.73 m²/BSA)(BSA/1.73 m²) = GFR and nothing else. --Dr. Hartwig Raeder (talk) 14:56, 10 June 2013 (UTC)

JAMA review

GFR and albuminuria in diagnosis of AKI/CKD doi:10.1001/jama.2015.0602 JFW | T@lk 21:49, 1 March 2015 (UTC)

GFR as a function of net filtration pressure

I've updated the definitions as used by Guyton and Hall Medical Physiology, and James Keenan's Mathematical Physiology which provide a clearer picture for those with basic calc knowledge what GFR actually means. It kind of looks messier now, but I think the information is relevant and more descriptive, so I don't know what to do with that. Bloomingdedalus (talk) 06:29, 24 June 2011 (UTC)

Dear Blooming Dedalus, Your Pressure Definition is wrong. The unit of the hydraulic conductivity is cm/min. The unit of the surface area is cm². So the unit of the filtration constant is ml/min. The unit of pressure is Pascal. So the unit of GRF is Paml/min. But: The correct unit of GFR is ml/min. WHERE IS YOUR MISTAKE? Please read Chapter 3 Paragraph Y on my Website www.nierenfunktionseinheit.de (sorry, only in German; but some English language paragraphs at the end)-- Dr. Hartwig Raeder (talk) 11:39, 24 November 2012 (UTC) The correct answer is as follows. See Darcy's Law. Id est Q = - (kA)(PB - PA)/µL with Q = total discharge (ml/min), k = permeability (cm²), A = area (cm²), (PB-PA) = pressure difference (Pa), µ = viscosity (Pa min), L = length (cm). Now ml/min = (cm² cm² Pa):(Pa min cm). Quod erat demonstrandum. -- Dr. Hartwig Raeder (talk) 19:01, 24 November 2012 (UTC)

Before I came here, I surmised that GFR wuz nothing but a three word term for "Urinary Volume per unit of time". That's what Dr. Hartwig Raeder is saying; mL/min (assuming that he is incorrectly using a lower-case eL for litres). In other words, creatinine clearance rate iz not an approximation for Glomerular filtration rate. All you need to calculate GFR is a twenty-four hour urine collection after consuming some standard amount of fluid (barring usability of other physics in the doctor's message). Levels of creatinine in blood are a warning by themselves, because they indicate that kidneys are not clearing enough creatinine.
The best way to keep your kids out of hot water is to put some dishes in it.
[2] 23:30, 26 January 2014 (UTC) — Preceding unsigned comment added by 75.156.176.23 (talk)

You are totally wrong. GFR is the glomerular filtration rate. It is by definition exactly the same as the creatinine clearance. It is the plasma volume that is cleared from creatinine in every minute. --Dr. Hartwig Raeder (talk) 13:03, 28 January 2014 (UTC)

Your definition iz useless, and not a part of the creatinine article. Creatinine iz a solid, which would be grams per hour (g/hour). Creatinine levels are a problem on their own. Creatinine levels in blood are measured on their own in blood tests. If kidneys are not removing enough of it, then blood levels will increase, or become unreasonable. How can glomerular filtration rate (mL/hour) be different from urinary volume over time (mL/hour)? [3] 75.156.176.23 (talk) 03:43, 1 February 2014 (UTC)

You are totally wrong. GFR = 100 ml/min = 144 l/d. GFR and production of primary urine are the same. The answer to your question is very easy. You must not forget the tubuli. They remove nearly all water from the primary urine. The result is your daily amount of urine. --Dr. Hartwig Raeder (talk) 09:07, 14 April 2015 (UTC)

Normalization of GFR according to GFR(1.73 m²/BSA) - the only correct unit of renal function is ml/min

There are several mistakes: Creatinine Clearance CCr No.1: (1.25 mg/min):(0.01 mg/ml) = 125 ml/min is correct. No.2: "is often corrected" is wrong; correct is "to normalize". Both the GFR and the normalized GFR(1.73 m²/BSA) are correct. No.3: "expressed ... as mL/min/1.73 m²" is the wrong unit; correct is only and always ml/min. No.4: Normalization of GFR according to GFR(1.73 m²/BSA) does not change the physiological unit. Estimated values No.5: Correct is: Cockcroft-Gault and MDRD estimate GFR in ml/min. But: CKD-EPI formula: wrong unit "mL/min per 1.73 m²". Chronic kidney disease stages: No.6: Wrong unit mL/min/1.73 m². The unit for the absolute GFR and for the relative GFR is ml/min without any exception. No.7: For the classification into one of the six stages it is essential to use the normalized GFR(1.73 m²/BSA). You have to multiply the true or estimated GFR by 1.73 m² and to divide the result by the patient's BSA. For more details please read my website www.nierenfunktionseinheit.de It is in German language only, but some paragraphs at the end are in English. Dr. Hartwig Raeder, Bad Salzuflen, Germany -- Dr. Hartwig Raeder (talk) 14:00, 12 November 2012 (UTC)

Can you cite references for all these mistakes? If there is published material, I'll make the corrections - I actually came to this talk page to complain about the Corrected Ccr calculation and found your comments. Tarl.Neustaedter (talk) 20:27, 17 May 2013 (UTC)

Sorry, there are no references and no published material except my website. I did all the research by myself. I read, I thought, and I calculated, that's all. I invented the formula GFR(1.73 m²/BSA) and the expressions to normalize GFR and to antinormalize GFR(1.73 m²/BSA). Thank you for your comment. --Dr. Hartwig Raeder (talk) 13:53, 8 June 2013 (UTC)

Surely there are nephrology textbooks which have these formulas which can be referenced. If not, the original papers for the MDRD and the CKD-EPI publications should serve - I just don't know how to locate them. I'm familiar with the terms as an interested layman, but don't have easy access to textbooks used to teach the subject in detail. Tarl.Neustaedter (talk) 22:17, 8 June 2013 (UTC)

You will not find my formula in any of the textbooks. You will need my formula GFR(1.73 m²/BSA) for staging chronic renal failure in the five stages 1 to 5 and for classification of renal failure according to ICD-10 N18.1-5. For some purposes you have to antinormalize GFR(1.73 m²/BSA) according to GFR(1.73 m²/BSA)(BSA/1.73 m²) = GFR. The original MDRD and CDK-EPI papers by Levey et alii are full of mistakes. These formulae are of limited value only. All together there are about 100 different estimation formulae for GFR. I cannot recommend any single one of them. --Dr. Hartwig Raeder (talk) 15:42, 10 June 2013 (UTC)

The Cockcroft-Gault formula already is normalized by weight and age, if imperfectly, so when we validated it using ^99m,Tc-DTPA mGFR by Russell's method in , I insisted in not presuming units of body surface area. BTW, mGFR and Cr eGFR scale differently . Although in Adoplh Cr eGFR is close to the 2/3 power of body mass, and mGFR close to the 3/4 power of body mass that does not mean that eGFr and mGFR are best normalized by body surface area and Kleiber's Law respectively—see paper CarlWesolowski (talk) 22:36, 3 August 2016 (UTC)

References

Clarify KDOQI

Shouldn't the information under "Controversies regarding the KDOQI classification" also expand the acronym and perhaps link to reference 4? 203.10.76.15 (talk) 14:25, 9 August 2010 (UTC). I agree, but also ref. 8 contains spurious information, in specific "Plasma clearance of exogenous substances including iohexol and 51Cr-EDTA has been used as well but require estimates of body size, which decreases their precision." See Talk references below as well. There is no body scaling by surface area, urine production is not skin deep. What is true is that Cr CL is a horrible measurement of renal function. To wit, I think a separate section on mGFR is needed herein, and suggest that the basic theory of how best to do this was only published a few days ago . For example, that article shows the physiologic connection between bolus intravenous mGFR and constant infusion mGFR, which, due to a mistake made in the year 1915, has never before been made clear. I would ask that some of the experts in this group read that article and comment.CarlWesolowski (talk) 23:08, 3 August 2016 (UTC)

Measurement of Glomerular Filtration Rate using Plasma Sampling

I an probably missing something but does anyone know why there is no mention of the use of Cr-51 EDTA or Tc-99m DTPA for this test? -Therealmorris (talk) 07:48, 4 August 2016 (UTC)

Normalized to 1.73m² or not?

After age 40, GFR decreases progressively with age, by 0.4–1.2 mL/min per year.

The rest of the paragraph is so normalized, and you actually have to think hard to realize that this could be correct as written (in a formula where you neglect to multiply by the subject's surface area). Way too much requirement for the reader to read above the level of the text. Who is helping who, here? — MaxEnt 17:00, 28 March 2018 (UTC)