Creatinine and Kidney Function Quiz
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Questions and Answers

What is the primary purpose of the creatinine clearance test (CrCl)?

To provide a better estimation of kidney function than other tests.

What factors can influence the calculation of creatinine clearance?

Sex, age, weight, and race.

How does high creatinine concentration in urine relate to drug tests?

High creatinine levels indicate a pure test sample.

What is creatinine and how is it produced in the body?

<p>Creatinine is a chemical waste produced from muscle metabolism, resulting from creatine metabolism.</p> Signup and view all the answers

Why is creatinine considered a common indicator of kidney function?

<p>Its plasma level remains relatively constant and is less influenced by diet and hydration.</p> Signup and view all the answers

Under what circumstances might a doctor order a creatinine blood test?

<p>If there are signs of kidney disease.</p> Signup and view all the answers

What role does urine creatinine concentration play in detecting test integrity?

<p>It helps determine if the urine sample is pure or tampered with.</p> Signup and view all the answers

What does a depressed level of plasma creatinine indicate?

<p>Depressed levels of plasma creatinine are rare and usually not clinically significant.</p> Signup and view all the answers

What is creatinine and how is it produced in the body?

<p>Creatinine is a breakdown product of creatine phosphate in muscle, produced at a fairly constant rate based on muscle mass.</p> Signup and view all the answers

Explain the main role of the kidneys in relation to creatinine.

<p>The kidneys filter out creatinine from the blood through glomerular filtration and proximal tubular secretion.</p> Signup and view all the answers

What does an increase in serum creatinine levels indicate?

<p>An increase in serum creatinine levels indicates a deficiency in the filtering capacity of the kidneys.</p> Signup and view all the answers

How can creatinine clearance (CrCl) be calculated and what does it reflect?

<p>Creatinine clearance can be calculated using the levels of creatinine in urine and blood, reflecting the glomerular filtration rate (GFR).</p> Signup and view all the answers

What factors can affect the accuracy of GFR estimates in renal dysfunction?

<p>Factors such as ketoacidosis, cimetidine, and trimethoprim can reduce creatinine tubular secretion, affecting GFR accuracy.</p> Signup and view all the answers

Why might men have higher serum creatinine levels than women?

<p>Men generally have higher serum creatinine levels due to having more skeletal muscle mass compared to women.</p> Signup and view all the answers

What does a raised BUN-to-creatinine ratio suggest?

<p>A raised BUN-to-creatinine ratio may indicate a pre-renal problem such as volume depletion.</p> Signup and view all the answers

What is the significance of measuring serum creatinine in clinical practice?

<p>Measuring serum creatinine is crucial as it is the most commonly used indicator of renal function.</p> Signup and view all the answers

What are some common symptoms of kidney problems?

<p>Common symptoms include fatigue, swelling, changes in urine output, and high blood pressure.</p> Signup and view all the answers

Name two diseases associated with kidney inflammation.

<p>Glomerulonephritis and pyelonephritis are two diseases associated with kidney inflammation.</p> Signup and view all the answers

What is the primary method by which creatinine is removed from the blood?

<p>Creatinine is primarily removed from the blood by glomerular filtration in the kidneys.</p> Signup and view all the answers

How can blood creatinine concentrations relate to kidney function?

<p>Increased blood creatinine concentrations indicate impaired kidney function or decreased glomerular filtration rate.</p> Signup and view all the answers

What could increased blood creatinine levels indicate?

<p>Increased levels may indicate impaired renal function or urinary tract obstruction.</p> Signup and view all the answers

Which demographic factors can lead to decreased creatinine levels?

<p>Factors like small stature, decreased muscle mass, and pregnancy can lead to decreased creatinine levels.</p> Signup and view all the answers

What is the best test to measure kidney function?

<p>Creatinine clearance is regarded as the best test to measure kidney function.</p> Signup and view all the answers

List one condition that might cause a decrease in blood creatinine concentration.

<p>Advanced liver disease can cause a decrease in blood creatinine concentration.</p> Signup and view all the answers

What is GFR, and why is a normal range considered important for kidney function?

<p>GFR stands for Glomerular Filtration Rate, which is the rate at which blood is filtered in the kidneys. A normal GFR of more than 90 ml/min is important as it indicates proper kidney function and efficient waste elimination.</p> Signup and view all the answers

Explain the importance of urine creatinine (Ucr) in calculating GFR.

<p>Urine creatinine (Ucr) is critical in calculating GFR because it reflects the concentration of creatinine in urine, which helps determine how well the kidneys are filtering blood. It is used in the formula GFR = Ucr/Scr * UV.</p> Signup and view all the answers

Describe the procedure for measuring serum creatinine concentration using the Jaffe reaction.

<p>The serum creatinine concentration is measured by mixing a serum sample with a pH=4 picric acid reagent, then measuring absorbance at 505 nm at two time intervals. The concentration is calculated using the difference in absorbance values.</p> Signup and view all the answers

What factors influence the rate of substance elimination in the urine?

<p>The rate of substance elimination in urine is influenced by plasma concentration and excretory rate, GFR, and renal plasma flow (RPF). These factors determine how efficiently the kidneys can filter and excrete substances.</p> Signup and view all the answers

What happens to GFR as people age, and what is a typical value for adults over time?

<p>As people age, GFR typically declines, with a normal GFR being more than 90 ml/min in adults, decreasing to around 70 ml/min in the elderly even without kidney disease. This decline reflects natural aging processes in kidney function.</p> Signup and view all the answers

Study Notes

Creatinine

  • Is a breakdown product of creatine phosphate in muscle
  • Produced at a fairly constant rate, dependent on muscle mass
  • Synthesized in the liver, kidney, and pancreas from three amino acids: arginine, glycine, and methionine
  • 1-2% of creatine is spontaneously converted to creatinine daily
  • Filtered by the kidneys via glomerular filtration and proximal tubular secretion
  • Little to no tubular reabsorption occurs

Creatinine Blood Test

  • Used to assess creatinine levels
  • Ordered if a patient shows signs of kidney disease
  • Elevation indicates an under-excretion, suggesting kidney impairment
  • Depressed levels are rare and not clinically significant

Creatinine and Kidney Function

  • A major indicator of glomerular filtration rate (GFR) and renal function
  • Creatinine blood and urine levels can be used to calculate the creatinine clearance (CrCl), which reflects the GFR
  • In severe renal dysfunction, CrCl may be overestimated due to active creatinine secretion
  • Ketoacidosis, cimetidine, and trimethoprim reduce creatinine tubular secretion, improving the accuracy of GFR estimates in severe dysfunction
  • In the absence of secretion, creatinine acts similarly to insulin
  • A complete assessment of kidney function is gained by interpreting creatinine levels in blood (plasma) alongside urea levels

BUN-to-Creatinine Ratio

  • BUN stands for Blood Urea Nitrogen
  • Indicates problems beyond the kidney
  • An elevated urea level disproportionate to creatinine may suggest a pre-renal problem like volume depletion
  • Men typically have higher creatinine levels because they have more skeletal muscle mass
  • Vegetarians have lower creatinine levels

Blood Creatinine Concentration

  • A rise in blood creatinine level only occurs with significant damage to functioning nephrons
  • A simple and common test for assessing renal function
  • Normal values:
    • Male: 0.6-1.2 mg/dL
    • Female: 0.5-1.0 mg/dL

Symptoms of Increased Blood Creatinine

  • Fatigue and trouble sleeping
  • Loss of appetite
  • Swelling in the face, wrists, ankles, or abdomen
  • Lower back pain near the kidneys
  • Changes in urine output and frequency
  • High blood pressure
  • Nausea
  • Vomiting

Causes of Increased Blood Creatinine

  • Impaired renal function
  • Chronic nephritis
  • Urinary tract obstruction
  • Muscle disease (e.g., muscular dystrophy, poliomyelitis)
  • Congestive heart failure
  • Shock
  • Dehydration
  • Rhabdomyolysis

Causes of Decreased Blood Creatinine

  • Small stature
  • Decreased muscle mass
  • Advanced and severe liver disease
  • Pregnancy

Creatinine Clearance

  • Measured by a volume of plasma from which a measured amount of substance can be completely eliminated in the urine per unit of time
  • The best test to measure kidney function and determine the stage of kidney disease
  • Depends on:
    • Plasma concentration
    • Excretory rate
    • Glomerular filtration rate (GFR)
    • Renal plasma flow (RPF)
  • Normal GFR: >90 ml/min in adults
  • GFR declines with age, even in healthy individuals, reaching 70 ml/min
  • GFR = Ucr/Scr * UV, where:
    • Ucr = Urine creatinine
    • Scr = Serum creatinine
    • UV = Urine volume expressed in ml/min

Creatinine Measuring Principle

  • Colorimetric reaction (Jaffe reaction) of creatinine with alkaline picrate is measured kinetically at 505 nm

Creatinine Clearance Procedure

  • Blank: 1 mL reagent
  • Sample: 1 mL reagent, 100 µL sample
  • Standard: 1 mL reagent, 100 µL standard
  • Mix well, record absorbance A1 at 505 nm against reagent blank after 30 seconds
  • Record absorbance A2 at 505 nm 90 seconds after the first reading
  • Calculation: Concentration of serum creatinine = ((A2-A1) - AB) / ((A2-A1) - AB) * Concentration of standard

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Description

This quiz explores the role of creatinine in muscle metabolism and kidney function. It covers the importance of creatinine levels in assessing renal health and how creatinine clearance is calculated. Test your knowledge on the synthesis, excretion, and clinical significance of creatinine in medical diagnostics.

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