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Questions and Answers
What is the main purpose of the Cockcroft-Gault Formula?
What is the main purpose of the Cockcroft-Gault Formula?
- To calculate the glomerular filtration rate
- To determine the muscle mass of an individual
- To measure the serum creatinine level
- To estimate creatinine clearance (correct)
Why is the constant K different for males and females in the Cockcroft-Gault Formula?
Why is the constant K different for males and females in the Cockcroft-Gault Formula?
- Because females have a higher creatinine clearance
- Because females have a relatively lower muscle mass (correct)
- Because males have a higher serum creatinine level
- Because males have a higher glomerular filtration rate
What parameter is NOT used in the Cockcroft-Gault Formula?
What parameter is NOT used in the Cockcroft-Gault Formula?
- Age of the subject (correct)
- Sex of the subject
- Weight of the subject
- Serum creatinine level
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Study Notes
Renal Function Tests
- Kidney function tests include serum creatinine, creatinine clearance, GFR estimation, and serum urea.
Serum Creatinine
- Ideal test for kidney function because it is constant, freely filtered, endogenous, and not reabsorbed but 10% secreted.
Creatinine Clearance (GFR)
- Formula: U x V / P
- Normal range:
- Adults: 110 ml/min
- Elderly: 70 ml/min
- Limitations: urine collection
Functional Units of the Kidney
- The nephron: 1,000,000 to 1,300,000 nephrons per kidney
- Kidney functions:
- Regulation: water and electrolyte balance, acid-base balance, and arterial blood pressure
- Excretion: metabolic waste products and foreign chemicals
- Hormonal: secretion of erythropoietin, activation of vitamin D, and activation of angiotensinogen
- Metabolic: gluconeogenesis
Importance of Renal Function Tests
- Many diseases affect renal function
- Destruction of complete nephron or selective impairment of glomerular or tubular functions
Measurements
- Serum creatinine (Cr)
- Creatinine clearance
- Serum urea
- Electrolytes
Creatinine Clearance
- Definition: volume of plasma cleared from the substance excreted in urine per minute
- Formula: U x V / P
GFR Estimation
- Normal range:
- 20-40 years adults: about 110 ml/min
- Over 80 years & females: about 70 ml/min
- Children: related to surface area, similar to young adults
Cockcroft-Gault Formula
- Alternative method to calculate creatinine clearance using serum creatinine level, sex, and weight
- Constant (K) varies with sex:
- Males: 1.23
- Females: 1.04 (due to relatively lower muscle mass)
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