NPN and Renal Function Flashcards
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NPN and Renal Function Flashcards

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Questions and Answers

Creatinine is formed from the oxidation of which substance?

  • Oxidation of creatine (correct)
  • Metabolism of purines (correct)
  • Deamination of dibasic amino acids (correct)
  • Oxidation of protein

    • Which of the formulas below is the correct expression for creatinine clearance?

  • Creatinine clearance = P/V x U x 1.73/BSA (correct)
  • Creatinine clearance = P/V x U x BSA/1.73 (correct)
  • Creatinine clearance = U/V x P x 1.73/BSA
  • Creatinine clearance = U/P x V x 1.73/BSA (correct)

    • In the creatinine clearance formula, the term 1.73/BSA is used to:

  • Correct clearance for creatinine that is secreted by the renal tubules
  • Make the clearance measurement independent of filtrate flow rate (correct)
  • Adjust the clearance so that it is equal to inulin clearance (correct)
  • Normalize clearance making it independent of muscle mass (correct)

    • Urea is produced from the catabolism of which substances?

    <p>Proteins and amino acids</p> Signup and view all the answers

    Which of the following conditions is classified as renal-type aminoaciduria?

    <p>Hepatitis</p> Signup and view all the answers

    Creatinine is considered the substance of choice to measure endogenous renal clearance because:

    <p>Plasma levels are highly dependent upon diet</p> Signup and view all the answers

    Which statement regarding creatinine is true?

    <p>Serum creatinine is a more sensitive measure of renal function than creatinine clearance</p> Signup and view all the answers

    Given the following data, calculate the creatinine clearance: SERUM CREATININE 1.2 mg/dL, URINE CREATININE 120 mg/dL, URINE VOLUME 1.75 L, COLLECTION TIME 24 hours, BODY SURFACE AREA 1.80 m2. What is the result?

    <p>117 mL/min</p> Signup and view all the answers

    Select the primary reagent used in the Jaffe method for creatinine:

    <p>Phosphotungstic acid</p> Signup and view all the answers

    Urea concentration is calculated from the BUN by multiplying by a factor of:

    <p>2.14</p> Signup and view all the answers

    BUN is determined electrochemically by coupling the urease reaction to measurement of:

    <p>Carbon dioxide</p> Signup and view all the answers

    Study Notes

    Creatinine and Its Formation

    • Creatinine is formed from the oxidation of creatine, resulting in a waste product linked to muscle metabolism.
    • It is an "anhydride" created when creatine loses a water molecule or when creatine-phosphate loses a phosphoric acid molecule.

    Creatinine Clearance Calculation

    • The correct formula for creatinine clearance is given by: creatinine clearance = U/P x V x 1.73/BSA.
    • In this formula, U represents urine concentration, P represents plasma concentration, V is the urine volume, and BSA is body surface area.

    Normalization in Creatinine Clearance

    • The term 1.73/BSA in the creatinine clearance formula normalizes the measurement to account for variations in muscle mass between individuals.

    Urea Production

    • Urea is produced from the catabolism of proteins and amino acids, serving as a key marker in assessing renal function.

    Renal-Type Aminoaciduria

    • Fanconi's syndrome is classified as a renal-type aminoaciduria, linked to defects in the kidney that lead to increased amino acid loss in urine.
    • Non-renal disorders such as Wilson's disease, hepatitis, and homocystinuria may cause renal damage but are not classified as renal-type aminoacidurias.

    Creatinine as a Measurement Tool

    • Creatinine is the preferred substance to measure endogenous renal clearance due to its complete filtration by the glomerulus, despite some tubular secretion.
    • Overestimation of Glomerular Filtration Rate (GFR) may occur in normal individuals by 15% and up to 100% in patients with heavy proteinuria due to increased creatinine secretion.

    Creatinine Levels and Renal Disease

    • High serum levels of creatinine indicate reduced glomerular filtration function and can serve as an important diagnostic marker for renal impairment.

    Creatinine Clearance Calculation Example

    • Given data: Serum creatinine at 1.2 mg/dL, urine creatinine at 120 mg/dL, urine volume of 1.75 L over 24 hours, and body surface area of 1.80 m².
    • Calculated creatinine clearance from this data is approximately 117 mL/min.

    Jaffe Method for Creatinine Measurement

    • The primary reagent in the Jaffe method for measuring creatinine concentration is saturated picric acid combined with sodium hydroxide (NaOH).

    Blood Urea Nitrogen (BUN) to Urea Conversion

    • Urea concentration can be calculated from BUN by multiplying BUN by a factor of 2.14, reflecting the relationship in molecular weights.

    BUN Measurement Technique

    • BUN is determined electrochemically, where the urease reaction is coupled to a timed rate increase in conductivity for precise measurement.

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    Description

    Test your knowledge on non-protein nitrogen compounds and their role in renal function with these flashcards. This quiz covers key terms like creatinine and its formation, helping you understand important concepts in renal physiology.

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