A longitudinal study is conducted to assess changes in renal function over time in patients with recently diagnosed type 2 diabetes mellitus. An initial set of laboratory tests is obtained in newly enrolled patients to establish baseline renal function parameters. The following measurements are taken from a 42-year-old male volunteer. Which of the following is the best estimate of the filtration fraction in this patient assuming a urine flow of 1.0 mL/min?

Question

A longitudinal study is conducted to assess changes in renal function over time in patients with recently diagnosed type 2 diabetes mellitus.  An initial set of laboratory tests is obtained in newly enrolled patients to establish baseline renal function parameters.  The following measurements are taken from a 42-year-old male volunteer.  Which of the following is the best estimate of the filtration fraction in this patient assuming a urine flow of 1.0 mL/min?

Quizplus · Accepted Answer

11ec160b_3cf4_08ee_9249_33a95a4c006c_MD0001_00 Filtration fraction (FF) is the fraction of plasma flowing through the glomeruli that is filtered across the glomerular capillaries into Bowman's space. It can be thought of as the ratio between the glomerular filtration rate (GFR) and renal plasma flow (RPF): GFR can be calculated using the inulin or creatinine clearance, as these substances are freely filtered at the glomerulus and have relatively insignificant tubular reabsorption or secretion. RPF can be determined using the para-aminohippuric acid (PAH) clearance as almost all the PAH entering the kidneys is excreted in the urine (mostly via tubular secretion). The clearance (C) of any given substance S can be calculated as: In this example, creatinine and PAH clearances can be calculated as: C_Creatinine = (110 mg/dl x 1 ml/min) / 1.1 mg/dl = 100 ml/min C_PAH = (100 mg/ml x 1 ml/min) / 0.2 mg/ml = 500 ml/min From these values, FF can then be calculated as (100 ml/min) / (500 ml/min) = 0.2 or 20%, which is the typical filtration fraction for a healthy individual. Educational objective: The glomerular filtration rate (GFR) can be estimated by the inulin or creatinine clearance, while the renal plasma flow (RPF) is calculated using the para-aminohippuric acid clearance. The filtration fraction (FF = GFR / RPF) is the fraction of the RPF that is filtered across the glomerular capillaries into Bowman's space. It is usually equal to 20% in healthy individuals.

A Longitudinal Study Is Conducted to Assess Changes in Renal