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Kidney diseases and failure 1 nefro.ppt 8.5.2010 2 Repetition of physiology Regulation of water, electrolyte (blood pressure!) and acidobasic balance Removal of metabolic endproducts, foreign substances and toxins (not everything – small molecules soluble in water) Urea (carbamid), creatinine, uric acid Endocrine function (renin and erytropoetin) 2*800 000 – 1 200 000 nephrons Cortex and medulla Special blood supply : 1000 ml/min = 20% CO nefro.ppt 8.5.2010 3 Filtration and clearance Blood (plasma) flow and filtration is stable and independent on blood pressure (GFR = 2 ml/s, 120 ml/min, 180 l/d) Filtration fraction: Ratio between filtration and plasma flow : 120/600 = 0,20 (20 %) Clearance: Virtual amount of urine, which is cleared from a substance in a time unit Clearance is dependent on Filtration Tubular secretion and resorbtion nefro.ppt 8.5.2010 4 nefro.ppt 8.5.2010 5 Proteinuria Glomerular membrane = ultrafilter, the result is a solution similar to plasma but less protein The pore diameter allows the passage of molecules < 30 kDa and the basal membrane has a negative charge But it is10 g/d, in filtrate and only 25 mg in urine Variable according to physical activity and postural position nefro.ppt 8.5.2010 6 MEASUREMENT and ASSESMENT OF GFR Clearance of a substance which is only filtered = GFR Clearance = [U]/[P]*V [U][P] = cc in urine and plasma V = volume of urine Clearance = volume of plasma cleared nefro.ppt 8.5.2010 7 MEASUREMENT and ASSESMENT OF GFR Clearance = [U]/[P]*V [U][P] = cc in urine and plasma V = volume of urine Clearance = volume of plasma cleared Inulin (polysaccharide) Endogenous creatinine – not very exact Problems – 24h urine, method and secretion nefro.ppt 8.5.2010 8 ASSESMENT OF GFR Assesement from serum creatinine [Krea]*GFR = k GFR = k/[Krea] It is not so simple Creatinine syntheis is not stable: Age, muscle mass, meat in food… Not only filtered But cheap and simple nefro.ppt 8.5.2010 9 Theoretical association between serum creatinine and GFR 1600 1400 1200 1000 800 600 400 200 0 1,5 nefro.ppt 1,3 1,1 0,9 0,7 0,5 0,3 GFR, ml/min 8.5.2010 UriSed 10 nefro.ppt 8.5.2010 11 nefro.ppt 8.5.2010 Classification of National Kidney Foundation USA, 2005 12 Grade GFR, ml/s Prevalence, USA, % SR 1 > 1,5 or normal GFR 3,3 165 000 2 1,0 – 1,49 slightly GFR 3,0 150 000 3 0,5 – 0,99 midlle GFR 4,3 210 500 4 0,25 – 0,49 severe GFR 0,2 10 000 5 < 0,25 Kidney failure 0,2 10 000 nefro.ppt 8.5.2010