Acute Kidney Injury Flashcards
(167 cards)
What 3 principles are desirable in theory for a good assessment of renal function?
- Measurable
- Reproducible
- Consistent
Which of the following is not a desirable, theoretical good assessment of renal function?
A. Reproducible
B. Consistent
C. Measurable
D. Traceable
D. Traceable
What is used as a measurement of renal function?
GFR/eGFR
What is the equation for GFR?
[X]urine x urine flow rate / [X] plasma
What is the ideal criteria for a marker of GFR?
Principles of GFR marker: GFRR
• Gain: Appear in plasma at constant rate
• Filtered: Freely filtered at glomerulus
• Reabsorbed: Not reabsorbed or secreted by renal tubule
• Renal: Does not undergo extra-renal elimination
Which of the following is not a criteria for a marker used to estimate GFR?
A. Appear in the plasma at a constant rate
B. Freely filtered at the glomerulus
C. Reabsorbed/secreted by renal tubule
D. Does not undergo extra-renal elimination
C. Reabsorbed/secreted by renal tubule
What is the most commonly used marker for estimation of GFR?
A. Inulin
B. Cystatin
C. Creatinine
D. Urea
C. Creatinine
What is inulin and why is it good as an exogenous marker of GFR?
Why may it not be useful?
Plant polysaccharide of fructose.
Constant injection of inulin for 3 hour at 18mg/min with timed urine and blood collection to measure inulin at midpoints of collection period
+ Gold standard
+ Fulfils marker criteria (constant, not produced elsewhere, not secreted/absorbed, only renally excreted)
+ Comprehensive assessment via blood and urine output/sampling
- Time-consuming
- Resources
- Difficult to perform
What is cystatin and why is it good as an marker of GFR?
Why may it not be useful?
Cysteine protease inhibitor present on surface of nucleated cells shed into plasma and excreted by glomerular filtration
+ More stable than creatinine
+ Less interpersonal and intrapersonal variation
+ Better for elderly populations
+ Freely filtered, reabsorbed and metabolised by PT cells, not produced elsewhere, only renally excreted)
+ 13kDa
- Expensive
- Difficult (laboratory specific)
- Not validated
What is Creatinine and why is it good as an marker of GFR?
Why may it not be useful?
Metabolic product of creatine and phosphocreatine released at a constant rate by the body
Note: Plasma creatinine inversely related to GFR by 2 thus halving GFR ≈ x2 plasma creatinine concentration
+ Does not bind plasma proteins
+ Freely filtered
+ Little reabsorption
+ Low M/w 113Da
- Secreted by tubules (breakdown from muscle) - Increased error at lower GFR
- Relations to muscle mass - Inaccuracy in GFR determination by creatinine clearance due to collection and measurement
- Insensitive in acute kidney injury (AKI)
- Deranged in diet (meat), muscle mass (elevated), age (decrease), vegetarians (decrease),
- Drugs interfere: Trimethoprim, cimetidine compete for secretion and other substances (bilirubin, cephalosporin, high glucose)
What is Urea and why is it good as an marker of GFR?
Why may it not be useful?
Metabolic product of amino acids and exogenously acquired from protein intake
+ Freely filtered
+ Low M/w of 60Da
- 50% reabsorbed by PCT depending on water/Na reabsorption
- Deranged by liver disease (reduced urea plasma levels)
- Proteinolysis in the intestines raises urea
Which of the following markers is useful in elderly populations and has less interpersonal variation?
A. Inulin
B. Cystatin
C. Creatinine
D. Urea
B. Cystatin
Which of the following markers is endogenous and does not bind plasma proteins?
A. Inulin
B. Cystatin
C. Creatinine
D. Urea
C. Creatinine
Which of the following markers is endogenous and can be interfered with in AKI or Drugs?
A. Inulin
B. Cystatin
C. Creatinine
D. Urea
C. Creatinine
Which of the following markers is endogenous and is freely filtered but up to 50% is reabsorbed by PCT?
A. Inulin
B. Cystatin
C. Creatinine
D. Urea
D. Urea
What are the indications when clearance measurements based on serum creatinine may be inaccurate?
- Old age
- BMI
- MSK diseases
- Paraplegia/Quadriplegia
- Diet (carnivorous or vegetarian)
- Rapidly changing kidney function
- Pregnancy
What is the relationship between age and GFR?
Increasing age from 20 onwards leads to a gradual, physiological reduction in GFR
How can eGFRs be calculated? List the main formulas used.
1. MDRD: Formula to estimate GFR • Computerised • Useful is stable creatinine • Clinically used • Modifier for F (0.742) and Black (1.21)
• Less accurate if near normal GFR
- CKD-EPI: Formula estimating GFR
• Best estimation of GFR
• Clinically used (for donors)
• Modifier for Age (0.993), F (1.018), Black (1.159)
• Not validated yet (used for donors)
- Cockcroft-Gault Equation: Based on serum creatinine alone
• Advised for narrow therapeutic index drugs
- Inaccurate for rapidly changing creatinine levels
- Uses IBW at extremes of BW
- Adults only
- Not adjusted for SA
Which of the following equations is used for donors and gives the best estimation of GFR?
A. CKD-EPI
B. Cockcroft-Gault Equation
C. MDRD
A. CKD-EPI
Which of the following equations is used for clinically and useful is stable creatinine?
A. CKD-EPI
B. Cockcroft-Gault Equation
C. MDRD
C. MDRD
Which of the following equations is used when narrow therapeutic index drugs are used?
A. CKD-EPI
B. Cockcroft-Gault Equation
C. MDRD
B. Cockcroft-Gault Equation
Which of the following equations is only applicable to adults?
A. CKD-EPI
B. Cockcroft-Gault Equation
C. MDRD
B. Cockcroft-Gault Equation
What relationship does renal blood flow have on kidney function? What endogenous marker is used? Equation used to calculate RPF?
Renal blood flow (Renal plasma flow ≈ RPF) ≈ hydraulic pressure in glomerulus based on afferent and efferent arteriolar radius ≈ ∆ GFR
- Kidneys take 20% CO ≈ 20% of 5L/min ≈ 1/L min
Which of the following is a marker for Renal Plasma Flow (RPF)?
A. Butyric acid
B. Urea
C. Para-aminohippurate
D. Creatining
C. Para-aminohippurate