Chap44N Renal Physiology

  1. Clinical Assessment of Glomerular Filtration Rate?
    • 1. Renal Clearence: 
    • GFR = urine [X]× urine volume (in ml per unit time)/plasma [X]

    • There are a number of substances that have been used clinically to estimate GFR
    • - Inulin 
    • - Radiolabeled compounds—such as iothalamate or DTPA
    • - Creatinine—the most widely used estimate of GFR is the 24-hour creatinine clearance (CrCl)

    • 2. Plasma markers: 
    • - Plasma Creatine 
    • - Plasma Urea 
    • - Plasma cystatin C
  2. Mathematical formulas developed to improve the accuracy of PCr estimation of GFR?
    • The three most widely used are the
    • - Cockcroft-Gault,
    • - Modification of diet in renal disease (MDRD)
    • - Chronic kidney disease epidemiology collaboration (CKD-EPI) formula.
  3. Cockcroft Gault formula?
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    A GFR estimate should be obtained in all patients with renal impairment(rather than a PCr alone), and the recommended method is through the use of the four-variable MDRD formula or Cockcroft-Gault formula.
  4. MDRD formula?
    • A series of formulas derived from data collected in patients with severe renal impairment. 
    • More complex but more accurate than the Cockcroft-Gault.
    • The simplest estimate of GFR is the four-variable equation (PCr, age,sex, and ethnicity)
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Chap44N Renal Physiology