Renal function assessment, Lecture notes of Medicine

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about:blank Assessment of renal function 1 Assessment of renal function 1 Kidney function: -Kidney function Waste excretion 0 Hormone synthesis D Acid-base balance 1 Gluconeogenesis. -NEPHRON = functional unit of kidney -Glomerular filtration rate = 120ml/min normal (7.2L/hour) Best measure of kidney function ~Age related decline approximately [ml/min per year Measuring GFR: -GFR and Clearance (0 We can use clearance to calculate GFR (1 The volume of plasma that can be completely cleared of a marker substance in unit time [1 If marker is not bound to serum proteins, freely filtered at the glomerulus, and not secreted/teabsorbed by tubular cells, Clearance (C)= GFR ( Atany one time: C=(U x VP © U—urinary cone; P — plasma cone Inulin clearance is gold-standard measure of GFR (0 S.2KD fructose polymer 1 Neutral charge 1 Freely filtered (Not processed by tubular cells (0 Widely regarded as “The perfect marker’ of GFR Steady state infusion is required (0. Measurement of inulin concentration is not simple Research tool only -GFR can be estimated by either giving pt an exogenous substance to clear or just measuring something already in the blood and filtered -Clinically viable measures of GFR O_ Single injection plasma clearance measurements: 0 \CrEDTA 0 Tc-DTPA © Tohexol -Endogenous markers of GFR (Same clearance characteristics as the ideal injectable marker: ‘© Not plasma protein bound © Freely filtered at glomerulus 0 Not modified by tubules (0 With steady state production (when renal function not changing rapidly) © Clearance = (Ux VP 11 Blood urea was the first endogenous marker of GFR ‘0 By-product of protein metabolism Freely filtered at glomerulus Variable (30-60%) reabsorption by tubular cells Dependent on nutritional state, hepatic function, GI bleeding Also reduced in patients with low protein intake Very limited clinical value eocooo 1/4