NPN and Renal Function Flashcards

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.

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.