Introduction Renal clearance describes the amount (volume) of plasma that is completely cleared by the kidneys per unit time in other words it reflects the excretion of a substance (e.g., medications) this depends on login to view 2 more bullets clearance decreases gradually with age but may have acute changes due to pathology equation C(x) = (UxV) / Px login to view 4 more bullets Clearance ratios C(inulin) C(inulin) = GFR inulin is freely filtered across glomerular capillaries login to view 2 more bullets inulin is a reference substance called a glomerular marker C(x) / C(inulin) > 1.0 C(x) > GFR interpretation login to view 3 more bullets C(x) / C(inulin) < 1.0 C(x) < GFR interpretation login to view 2 more bullets