Renal function test interpretation MCQs With Answer

Introduction: This question set focuses on interpretation of renal function tests for M.Pharm students preparing for clinical pharmacy roles. It covers laboratory markers (serum creatinine, BUN, eGFR, creatinine clearance), urine indices (ACR, proteinuria, sediment, specific gravity, osmolality), functional calculations (Cockcroft–Gault, MDRD, CKD-EPI, FENa, FeUrea) and biomarkers (NGAL, NAG) used in acute and chronic kidney disease. Emphasis is on integrating test results with clinical scenarios — differentiating prerenal, intrinsic and postrenal causes, recognizing limitations of equations in acute settings, drug-related nephrotoxicity, and staging CKD. These MCQs are designed to deepen interpretation skills needed for safe medication management in patients with renal impairment.

Q1. Which single laboratory finding most strongly suggests a prerenal acute kidney injury (AKI) rather than intrinsic renal damage?

• Fractional excretion of sodium (FENa) of 0.5%
• Urine sediment with muddy brown granular casts
• Fractional excretion of sodium (FENa) of 5%
• Urine osmolality of 200 mOsm/kg

Correct Answer: Fractional excretion of sodium (FENa) of 0.5%

Q2. A 65-year-old male has serum creatinine 2.0 mg/dL (baseline 1.0 mg/dL). Which statement about estimated GFR (eGFR) in this acute rise is most accurate?

• eGFR equations (MDRD/CKD-EPI) provide reliable immediate GFR estimates during acute creatinine changes
• Doubling of serum creatinine approximately reflects a 50% reduction in GFR but eGFR equations will lag and be unreliable in acute settings
• eGFR should be multiplied by 1.5 to account for acute rise
• Serum creatinine is unaffected by muscle mass in acute AKI

Correct Answer: Doubling of serum creatinine approximately reflects a 50% reduction in GFR but eGFR equations will lag and be unreliable in acute settings

Q3. Which method is preferred for quantifying albuminuria for CKD staging from a random urine sample?

• 24-hour urine total protein collection
• Spot urine albumin-to-creatinine ratio (ACR)
• Dipstick testing for protein
• Urine protein electrophoresis

Correct Answer: Spot urine albumin-to-creatinine ratio (ACR)

Q4. A patient has BUN 56 mg/dL and serum creatinine 1.8 mg/dL. Which interpretation is most consistent with these values?

• BUN:Creatinine ratio ~31 suggesting prerenal azotemia
• BUN:Creatinine ratio ~10 indicating intrinsic renal failure
• BUN:Creatinine ratio cannot be used clinically
• BUN:Creatinine ratio indicates postrenal obstruction definitively

Correct Answer: BUN:Creatinine ratio ~31 suggesting prerenal azotemia

Q5. Which statement about Cockcroft–Gault (CG) equation is correct when dosing renally excreted drugs?

• CG estimates creatinine clearance and includes body weight; it may overestimate renal function in obese patients unless adjusted
• CG directly provides measured GFR and is unaffected by age
• CG uses serum cystatin C instead of creatinine
• CG is the most accurate estimate in acute kidney injury

Correct Answer: CG estimates creatinine clearance and includes body weight; it may overestimate renal function in obese patients unless adjusted

Q6. Which urine finding most strongly points toward glomerulonephritis rather than tubular injury?

• Red blood cell (RBC) casts and dysmorphic RBCs
• High specific gravity with hyaline casts
• Muddy brown granular casts
• Isosthenuria with bland sediment

Correct Answer: Red blood cell (RBC) casts and dysmorphic RBCs

Q7. In a patient on loop diuretics where FENa may be unreliable, which fractional excretion helps distinguish prerenal azotemia?

• Fractional excretion of urea (FeUrea) <35%
• Fractional excretion of potassium >10%
• Fractional excretion of bicarbonate <5%
• Fractional excretion of phosphate >50%

Correct Answer: Fractional excretion of urea (FeUrea) <35%

Q8. A spot urine albumin-to-creatinine ratio (ACR) is 450 mg/g. How is albuminuria classified?

• A3 — severely increased albuminuria
• A1 — normal to mildly increased albuminuria
• A2 — moderately increased albuminuria
• Not albuminuric

Correct Answer: A3 — severely increased albuminuria

Q9. Which biomarker rises earliest in acute tubular injury and is useful for early detection before creatinine increases?

• Neutrophil gelatinase-associated lipocalin (NGAL)
• Serum urea nitrogen (BUN)
• Serum creatinine
• Urine dipstick protein

Correct Answer: Neutrophil gelatinase-associated lipocalin (NGAL)

Q10. Which change in laboratory values is most characteristic of postrenal obstruction in early stages?

• Initially elevated BUN:Cr ratio with variable urine sediment; may progress to intrinsic patterns if prolonged
• Immediately low BUN and low creatinine
• Always normal urine osmolality from onset
• Proteinuria >3.5 g/day as the first finding

Correct Answer: Initially elevated BUN:Cr ratio with variable urine sediment; may progress to intrinsic patterns if prolonged

Q11. When estimating GFR for chronic kidney disease staging, which equation is generally more accurate across populations, especially at higher GFRs?

• CKD-EPI equation
• Cockcroft–Gault equation
• Urea clearance formula
• Mendel equation (fictional)

Correct Answer: CKD-EPI equation

Q12. A hospitalized patient after contrast exposure has a rise in serum creatinine by 0.6 mg/dL within 48 hours. This most likely meets the definition of:

• Contrast-induced nephropathy (contrast-associated AKI)
• Chronic kidney disease progression only
• Nephrotic syndrome
• Urinary tract infection

Correct Answer: Contrast-induced nephropathy (contrast-associated AKI)

Q13. A patient with chronic low muscle mass has a “normal” serum creatinine of 0.6 mg/dL. Which interpretation is correct regarding renal function?

• Serum creatinine underestimates kidney dysfunction; estimated GFR may be higher than true GFR
• Serum creatinine overestimates kidney impairment in low muscle mass
• Creatinine-based eGFR is perfectly accurate regardless of muscle mass
• Low creatinine always rules out renal impairment

Correct Answer: Serum creatinine underestimates kidney dysfunction; estimated GFR may be higher than true GFR

Q14. Which urine index best indicates intact tubular concentrating ability?

• Urine osmolality >500 mOsm/kg in the setting of dehydration
• Urine osmolality = plasma osmolality at 300 mOsm/kg during dehydration
• Isosthenuria in hypovolemia
• Persistent urine osmolality <100 mOsm/kg despite dehydration

Correct Answer: Urine osmolality >500 mOsm/kg in the setting of dehydration

Q15. In differentiating prerenal from intrinsic acute kidney injury, which combination is most consistent with intrinsic (ATN) injury?

• FENa 3%, urine sodium high, muddy brown casts present
• FENa 0.4%, urine osmolality 700 mOsm/kg, bland sediment
• BUN:Cr ratio 35, FeUrea <35%
• Low urine sodium <20 mmol/L with concentrated urine

Correct Answer: FENa 3%, urine sodium high, muddy brown casts present

Q16. Which laboratory approach is best when estimating drug dosing for an elderly patient with rapidly changing creatinine?

• Use measured creatinine clearance from timed urine collection if feasible and repeat frequently
• Rely solely on a single eGFR from MDRD without clinical correlation
• Double the dose because elderly patients metabolize drugs faster
• Use history only and ignore laboratory values

Correct Answer: Use measured creatinine clearance from timed urine collection if feasible and repeat frequently

Q17. Which urinary finding most specifically supports tubular proteinuria rather than glomerular proteinuria?

• Low-molecular-weight proteins (e.g., β2-microglobulin) in urine with relatively low albumin excretion
• High selective albuminuria >3.5 g/day
• Heavy albuminuria with dysmorphic RBCs
• Positive urine nitrite test

Correct Answer: Low-molecular-weight proteins (e.g., β2-microglobulin) in urine with relatively low albumin excretion

Q18. Which interpretation of a 24-hour creatinine clearance result is correct if measured clearance is 55 mL/min but eGFR by CKD-EPI is 40 mL/min/1.73 m²?

• Measured creatinine clearance may overestimate GFR due to tubular secretion of creatinine; use clinical context
• CKD-EPI always overestimates and should be ignored
• Measured creatinine clearance is invalid and must equal CKD-EPI
• Both tests are identical measures of GFR and cannot differ

Correct Answer: Measured creatinine clearance may overestimate GFR due to tubular secretion of creatinine; use clinical context

Q19. Which drug-related pattern on renal tests is most characteristic of aminoglycoside nephrotoxicity?

• Acute tubular necrosis pattern with rising creatinine over days, granular casts, and elevated urinary biomarkers like NGAL
• Isolated increase in BUN without creatinine change
• Immediate anaphylactic drop in GFR within minutes
• Selective nephrotic-range proteinuria without sediment changes

Correct Answer: Acute tubular necrosis pattern with rising creatinine over days, granular casts, and elevated urinary biomarkers like NGAL

Q20. For chronic kidney disease staging, which combination of eGFR and albuminuria category corresponds to higher risk and requires closer management?

• eGFR 40 mL/min/1.73 m² (G3b) with ACR 200 mg/g (A2)
• eGFR 95 mL/min/1.73 m² (G1) with ACR <30 mg/g (A1)
• eGFR 60–89 mL/min/1.73 m² (G2) with ACR <30 mg/g (A1)
• eGFR >90 mL/min/1.73 m² with ACR <30 mg/g

Correct Answer: eGFR 40 mL/min/1.73 m² (G3b) with ACR 200 mg/g (A2)

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