MCQs on Kidney Function (KFT)
1. Which of the following is the best routine test for glomerular filtration rate (GFR)?
• A) Serum creatinine
• B) Urea clearance
• C) Inulin clearance
• D) Serum uric acid
Answer: C) Inulin clearance
Explanation: Inulin clearance is considered the gold standard for measuring GFR as inulin is freely filtered, not reabsorbed, secreted, or metabolized. Although serum creatinine is commonly used due to practicality, it slightly overestimates GFR because of tubular secretion. Hence, inulin clearance provides the most accurate measurement.
2. Which substance is most commonly used in routine practice for estimating GFR?
• A) Urea
• B) Creatinine
• C) Inulin
• D) Cystatin C
Answer: B) Creatinine
Explanation: Serum creatinine is the most widely used marker in clinical practice for estimating GFR. It is a muscle metabolism byproduct, freely filtered at glomeruli, and only slightly secreted. Despite some variability with age and muscle mass, its widespread availability and utility make it the preferred choice in routine settings.
3. The normal range of serum creatinine in adult males is:
• A) 0.3 – 0.6 mg/dL
• B) 0.6 – 1.2 mg/dL
• C) 1.2 – 2.0 mg/dL
• D) 2.0 – 3.0 mg/dL
Answer: B) 0.6 – 1.2 mg/dL
Explanation: Serum creatinine in healthy adult males typically ranges from 0.6–1.2 mg/dL, while in females it is slightly lower due to lesser muscle mass. Elevated values usually indicate impaired renal function. This marker remains central to renal assessment, but interpretation must consider muscle bulk, age, and physiological conditions.
4. Which test is considered the most reliable marker of early glomerular damage?
• A) Serum creatinine
• B) Microalbuminuria
• C) Urea clearance
• D) Cystatin C
Answer: B) Microalbuminuria
Explanation: Microalbuminuria (30–300 mg/day) is an early marker of glomerular injury, particularly in diabetic nephropathy and hypertension. It appears before significant proteinuria or elevated creatinine levels. Detecting it enables early intervention, slowing CKD progression and reducing cardiovascular risk. Thus, microalbuminuria testing is essential in high-risk patient populations.
5. Which test is least reliable for estimating kidney function?
• A) Serum urea
• B) Creatinine clearance
• C) Inulin clearance
• D) Cystatin C
Answer: A) Serum urea
Explanation: Serum urea is influenced by diet, hydration, liver function, and catabolism, making it an unreliable marker for kidney function. In contrast, creatinine clearance and inulin clearance better reflect glomerular filtration. Still, urea is sometimes useful in differentiating pre-renal from renal causes of elevated nitrogenous waste (azotemia).
6. Which of the following ratios helps differentiate pre-renal from renal causes of azotemia?
• A) Creatinine clearance/Serum creatinine
• B) Urea/Creatinine ratio
• C) Albumin/Creatinine ratio
• D) Sodium/Potassium ratio
Answer: B) Urea/Creatinine ratio
Explanation: The urea/creatinine ratio differentiates pre-renal from renal azotemia. In pre-renal states, increased tubular reabsorption of urea elevates the ratio (>20:1). In intrinsic renal disease, the ratio is usually normal (10–15:1). Hence, this ratio provides a simple diagnostic clue in evaluating kidney function abnormalities.
7. Which of the following tests evaluates tubular function?
• A) Creatinine clearance
• B) Urinary concentrating test
• C) Inulin clearance
• D) Serum creatinine
Answer: B) Urinary concentrating test
Explanation: Tubular function is assessed by concentrating and diluting tests, fractional excretion of electrolytes, and acidification studies. The urinary concentrating test (after water deprivation) checks the kidney’s ability to conserve water via ADH action. Impairment suggests tubular dysfunction, often seen in diabetes insipidus or interstitial renal disorders.
8. In which condition is fractional excretion of sodium (FeNa) <1%?
• A) Acute tubular necrosis
• B) Pre-renal azotemia
• C) Chronic kidney disease
• D) Glomerulonephritis
Answer: B) Pre-renal azotemia
Explanation: In pre-renal azotemia, kidneys conserve sodium aggressively to maintain perfusion, reducing FeNa to <1%. In intrinsic renal conditions like acute tubular necrosis, FeNa rises >2% due to tubular dysfunction. Thus, FeNa is a valuable tool in distinguishing pre-renal from intrinsic causes of acute kidney injury.
9. Blood urea nitrogen (BUN) to creatinine ratio in pre-renal failure is usually:
• A) Normal
• B) Increased
• C) Decreased
• D) Variable
Answer: B) Increased
Explanation: In pre-renal failure, decreased renal perfusion enhances tubular urea reabsorption, elevating BUN disproportionately compared to creatinine. This increases the BUN/creatinine ratio (>20:1). In contrast, intrinsic renal diseases impair tubular reabsorption, leading to a normal or decreased ratio. Hence, this ratio is useful in differential diagnosis.
10. Cystatin C is a marker of kidney function because it is:
• A) Secreted by renal tubules
• B) Produced by muscle metabolism
• C) Constantly produced by all nucleated cells
• D) A liver-derived protein
Answer: C) Constantly produced by all nucleated cells
Explanation: Cystatin C is a low molecular weight protein produced at a constant rate by all nucleated cells. It is freely filtered by glomeruli and not reabsorbed or secreted. Unlike creatinine, it is unaffected by age, sex, or muscle mass, making it a superior marker for GFR estimation.
11. Which of the following is the most important renal function assessed by creatinine clearance?
• A) Tubular secretion
• B) Glomerular filtration
• C) Tubular reabsorption
• D) Renal plasma flow
Answer: B) Glomerular filtration
Explanation: Creatinine clearance is widely used to estimate glomerular filtration rate (GFR). Creatinine is produced at a relatively constant rate from muscle metabolism, filtered freely at the glomerulus, and minimally secreted. Although it slightly overestimates GFR, creatinine clearance remains a practical tool for evaluating glomerular function in clinical settings.
12. Which of the following tests is most useful in detecting early diabetic nephropathy?
• A) Serum creatinine
• B) Microalbuminuria test
• C) Creatinine clearance
• D) Urea clearance
Answer: B) Microalbuminuria test
Explanation: Microalbuminuria is the earliest detectable sign of diabetic nephropathy, typically appearing before serum creatinine or creatinine clearance abnormalities. Early detection allows intervention with strict glycemic and blood pressure control, reducing progression to chronic kidney disease. Therefore, microalbuminuria testing is recommended in all diabetic patients for early diagnosis and management.
13. The substance that is freely filtered and neither secreted nor reabsorbed is:
• A) Creatinine
• B) Inulin
• C) Urea
• D) Glucose
Answer: B) Inulin
Explanation: Inulin, a fructose polysaccharide, is the gold standard marker for GFR measurement. It is freely filtered by the glomerulus, not metabolized, not reabsorbed, and not secreted. This makes its clearance an ideal reflection of true glomerular filtration. Other substances, such as creatinine, are slightly secreted, limiting accuracy.
14. Which test is best for measuring renal plasma flow (RPF)?
• A) Inulin clearance
• B) Creatinine clearance
• C) Para-aminohippuric acid (PAH) clearance
• D) Urea clearance
Answer: C) Para-aminohippuric acid (PAH) clearance
Explanation: PAH clearance is the gold standard for renal plasma flow measurement. PAH is freely filtered at the glomerulus and also secreted by the renal tubules, so almost all PAH entering the kidney is excreted in urine. Thus, its clearance closely approximates effective renal plasma flow (ERPF).
15. Which of the following is NOT a marker of glomerular function?
• A) Serum creatinine
• B) Urea
• C) PAH clearance
• D) Inulin clearance
Answer: C) PAH clearance
Explanation: PAH clearance primarily measures renal plasma flow, not glomerular filtration. In contrast, creatinine, urea, and inulin clearance all reflect glomerular function. Differentiating between glomerular filtration (GFR) and renal blood flow markers is essential in nephrology for accurate interpretation of kidney function and disease state.
16. Which protein in urine indicates glomerular permeability defects?
• A) Albumin
• B) Beta-2 microglobulin
• C) Myoglobin
• D) Hemoglobin
Answer: A) Albumin
Explanation: Albuminuria indicates glomerular dysfunction, as albumin normally does not cross the intact glomerular basement membrane. Its presence reflects increased permeability, often seen in diabetic nephropathy, glomerulonephritis, and hypertension. Persistent albuminuria is a hallmark of chronic kidney disease (CKD) and an important prognostic marker for renal and cardiovascular risk.
17. Which test is used to assess the kidney’s ability to acidify urine?
• A) Ammonium chloride loading test
• B) Inulin clearance test
• C) Creatinine clearance test
• D) Water deprivation test
Answer: A) Ammonium chloride loading test
Explanation: The ammonium chloride loading test evaluates distal tubular acidification capacity. In this test, ammonium chloride induces metabolic acidosis, and the kidney’s ability to excrete hydrogen ions is assessed by urine pH. Failure to acidify urine (<5.5) suggests renal tubular acidosis, an important tubular function defect.
18. In chronic kidney disease, which of the following decreases earliest?
• A) GFR
• B) Serum creatinine
• C) Serum potassium
• D) Serum bicarbonate
Answer: A) GFR
Explanation: A decline in GFR is the earliest detectable change in chronic kidney disease, preceding changes in serum creatinine or electrolytes. Serum creatinine may remain normal until about 50% of renal function is lost, highlighting the importance of GFR estimation for early CKD diagnosis and intervention.
19. Which test is preferred to monitor progression of chronic kidney disease (CKD)?
• A) Serum creatinine alone
• B) Estimated GFR (eGFR)
• C) Blood urea nitrogen
• D) Urine specific gravity
Answer: B) Estimated GFR (eGFR)
Explanation: eGFR, calculated using serum creatinine-based equations like MDRD or CKD-EPI, provides a more accurate reflection of kidney function than serum creatinine alone. It accounts for age, sex, and body size. Monitoring eGFR helps stage CKD, track disease progression, and guide therapy, making it the preferred monitoring tool.
20. Which of the following indicates tubular proteinuria?
• A) Albuminuria
• B) Beta-2 microglobulinuria
• C) Hemoglobinuria
• D) Myoglobinuria
Answer: B) Beta-2 microglobulinuria
Explanation: Tubular proteinuria results from defective tubular reabsorption of low molecular weight proteins like beta-2 microglobulin. In contrast, albuminuria reflects glomerular dysfunction, while hemoglobinuria and myoglobinuria are overflow proteinurias. Tubular proteinuria often occurs in conditions such as interstitial nephritis or exposure to nephrotoxic drugs.
21. Which of the following urine findings indicates impaired concentrating ability of kidneys?
• A) Fixed specific gravity (isosthenuria)
• B) High urine osmolality
• C) Alkaline pH
• D) Proteinuria
Answer: A) Fixed specific gravity (isosthenuria)
Explanation: Isosthenuria refers to urine with a fixed specific gravity around 1.010, similar to plasma. It indicates the kidneys have lost the ability to concentrate or dilute urine, often seen in chronic renal failure. This finding reflects advanced damage to tubular function, particularly affecting concentrating mechanisms.
22. Which parameter is used in the Cockcroft-Gault equation to estimate creatinine clearance?
• A) Blood urea
• B) Serum creatinine, age, weight, sex
• C) Serum albumin
• D) Serum uric acid
Answer: B) Serum creatinine, age, weight, sex
Explanation: The Cockcroft-Gault equation estimates creatinine clearance using serum creatinine, patient age, body weight, and sex. This formula approximates GFR and is widely used for drug dosing in renal impairment. It provides a convenient method for assessing renal function without performing a direct clearance test.
23. Which of the following is the earliest marker of glomerular injury?
• A) Serum creatinine
• B) Proteinuria
• C) Microalbuminuria
• D) Hematuria
Answer: C) Microalbuminuria
Explanation: Microalbuminuria, defined as urinary albumin excretion of 30–300 mg/day, is the earliest marker of glomerular injury, especially in diabetic nephropathy and hypertension. It precedes overt proteinuria and changes in serum creatinine. Early detection is critical for initiating therapy to prevent progression to chronic kidney disease.
24. Which of the following conditions causes prerenal azotemia?
• A) Acute tubular necrosis
• B) Hypovolemia
• C) Glomerulonephritis
• D) Polycystic kidney disease
Answer: B) Hypovolemia
Explanation: Prerenal azotemia results from reduced renal perfusion, commonly due to hypovolemia, dehydration, or heart failure. It is characterized by increased blood urea nitrogen (BUN) with relatively normal creatinine initially. Unlike intrinsic renal disease, kidney structure is intact, and prompt correction of perfusion can restore renal function.
25. Which of the following is true about urea clearance test?
• A) Gold standard for GFR
• B) Overestimates GFR
• C) Underestimates GFR
• D) Unreliable in CKD
Answer: C) Underestimates GFR
Explanation: Urea clearance underestimates GFR because urea is partly reabsorbed in renal tubules after filtration. Its excretion varies with hydration and protein intake, making it less reliable than creatinine or inulin clearance. However, it provides useful information in some settings where other methods are unavailable.
26. Which test best evaluates the kidney’s ability to concentrate urine?
• A) Water deprivation test
• B) PAH clearance
• C) Creatinine clearance
• D) Urea clearance
Answer: A) Water deprivation test
Explanation: The water deprivation test assesses the kidney’s ability to concentrate urine in response to dehydration. Normally, urine osmolality rises significantly after water deprivation. In diabetes insipidus, this response is impaired, helping differentiate central from nephrogenic causes when combined with desmopressin administration.
27. Which of the following is an endogenous marker of GFR?
• A) Inulin
• B) Iohexol
• C) Creatinine
• D) PAH
Answer: C) Creatinine
Explanation: Creatinine is an endogenous marker produced by muscle metabolism and widely used clinically to estimate GFR. While not perfect because of tubular secretion, it avoids the need for exogenous infusions like inulin or iohexol. This makes creatinine practical for routine monitoring of renal function in clinical settings.
28. In renal tubular acidosis, which of the following abnormalities is observed?
• A) Hyperkalemia
• B) Metabolic alkalosis
• C) Metabolic acidosis with normal anion gap
• D) Respiratory acidosis
Answer: C) Metabolic acidosis with normal anion gap
Explanation: Renal tubular acidosis (RTA) is characterized by defective tubular acid secretion or bicarbonate reabsorption, leading to a normal anion gap (hyperchloremic) metabolic acidosis. Depending on the type, patients may have associated hypokalemia or hyperkalemia. Diagnosis is confirmed by urine pH and specific functional tests.
29. Which of the following is an example of overflow proteinuria?
• A) Microalbuminuria
• B) Bence-Jones proteinuria
• C) Tubular proteinuria
• D) Post-renal proteinuria
Answer: B) Bence-Jones proteinuria
Explanation: Overflow proteinuria occurs when excessive low molecular weight proteins exceed the reabsorptive capacity of tubules. Bence-Jones proteins, seen in multiple myeloma, are classic examples. These free light chains are filtered in large quantities, leading to renal damage if persistent. This differs from glomerular or tubular proteinuria.
30. Which of the following is NOT a function of the kidney?
• A) Gluconeogenesis
• B) Regulation of acid-base balance
• C) Synthesis of erythropoietin
• D) Synthesis of albumin
Answer: D) Synthesis of albumin
Explanation: Albumin is synthesized in the liver, not the kidneys. The kidney’s functions include filtration, reabsorption, secretion, regulation of fluid-electrolyte and acid-base balance, blood pressure regulation (via renin), and synthesis of hormones such as erythropoietin and active vitamin D. Thus, albumin synthesis is not a renal function.
31. Which test substance is used to measure renal plasma flow (RPF)?
• A) Inulin
• B) Creatinine
• C) Para-aminohippuric acid (PAH)
• D) Urea
Answer: C) Para-aminohippuric acid (PAH)
Explanation: PAH clearance is used to estimate renal plasma flow (RPF) because it is almost completely filtered and secreted by the renal tubules, resulting in near-total excretion. This makes PAH clearance an excellent marker for effective renal plasma flow, unlike inulin or creatinine which primarily reflect GFR.
32. Which of the following tests detects early diabetic nephropathy?
• A) Serum creatinine
• B) Microalbuminuria estimation
• C) Urine dipstick for protein
• D) Creatinine clearance
Answer: B) Microalbuminuria estimation
Explanation: Microalbuminuria is the earliest indicator of diabetic nephropathy, preceding overt proteinuria and rise in serum creatinine. Detection of 30–300 mg/day urinary albumin helps in timely intervention with ACE inhibitors or ARBs, which can delay progression to chronic kidney disease and end-stage renal failure in diabetics.
33. Which of the following indicates nephrotic-range proteinuria?
• A) 100 mg/day
• B) 300 mg/day
• C) 1 g/day
• D) >3.5 g/day
Answer: D) >3.5 g/day
Explanation: Nephrotic syndrome is defined by proteinuria exceeding 3.5 g/day in adults, along with hypoalbuminemia, edema, hyperlipidemia, and lipiduria. Such heavy proteinuria indicates severe glomerular barrier damage, often due to minimal change disease, focal segmental glomerulosclerosis, or membranous nephropathy.
34. Which of the following increases serum creatinine without true renal dysfunction?
• A) Dehydration
• B) Increased muscle mass
• C) Diabetic nephropathy
• D) Glomerulonephritis
Answer: B) Increased muscle mass
Explanation: Serum creatinine depends on muscle mass since it originates from creatine metabolism. Athletes or individuals with high muscle bulk may have elevated serum creatinine without impaired kidney function. Conversely, elderly or malnourished patients may have deceptively low creatinine despite reduced GFR, hence creatinine must be interpreted cautiously.
35. Which urine test is useful for diagnosing Fanconi syndrome?
• A) Glucosuria with normal blood glucose
• B) Ketonuria
• C) Proteinuria
• D) Hematuria
Answer: A) Glucosuria with normal blood glucose
Explanation: In Fanconi syndrome, proximal tubular reabsorption defects lead to glucosuria despite normal plasma glucose, along with aminoaciduria, phosphate wasting, and bicarbonaturia. This constellation of findings reflects generalized proximal tubular dysfunction and is characteristic of this syndrome, which may be inherited or acquired from toxins or drugs.
36. Which of the following tests is most sensitive for detecting early renal dysfunction?
• A) Blood urea nitrogen (BUN)
• B) Serum creatinine
• C) Creatinine clearance
• D) Microalbuminuria
Answer: D) Microalbuminuria
Explanation: Microalbuminuria is the most sensitive indicator of early renal dysfunction, especially in diabetes and hypertension. BUN and creatinine rise later when substantial renal damage has already occurred. Creatinine clearance is useful but requires urine collection, making microalbuminuria estimation a preferred early screening tool.
37. Which electrolyte abnormality is commonly associated with chronic kidney disease (CKD)?
• A) Hypokalemia
• B) Hyperkalemia
• C) Hyponatremia
• D) Hypocalcemia
Answer: B) Hyperkalemia
Explanation: Hyperkalemia is common in CKD due to reduced renal excretion of potassium. This can cause life-threatening cardiac arrhythmias. Other common findings include metabolic acidosis, hypocalcemia, and hyperphosphatemia. Regular monitoring of electrolytes in CKD patients is essential to prevent complications and guide dietary or pharmacologic interventions.
38. What is the primary urinary abnormality in multiple myeloma?
• A) Albuminuria
• B) Hematuria
• C) Bence-Jones proteinuria
• D) Glycosuria
Answer: C) Bence-Jones proteinuria
Explanation: In multiple myeloma, malignant plasma cells produce monoclonal light chains that are filtered by the glomerulus and appear in urine as Bence-Jones proteins. These cause renal tubular damage and contribute to myeloma kidney. Standard dipsticks often miss them, requiring special tests such as electrophoresis for detection.
39. Which test is commonly used to monitor progression of chronic kidney disease?
• A) Serum creatinine
• B) Urine osmolality
• C) PAH clearance
• D) Uric acid levels
Answer: A) Serum creatinine
Explanation: Serum creatinine is routinely used to monitor progression of CKD as it reflects GFR decline. Though not as accurate as inulin clearance, it is practical for regular follow-up. Serial measurements, combined with estimated GFR (eGFR), provide a reliable picture of disease progression and treatment efficacy.
40. Which hormone, regulated by kidney function, stimulates red blood cell production?
• A) Renin
• B) Aldosterone
• C) Erythropoietin
• D) Vitamin D
Answer: C) Erythropoietin
Explanation: The kidneys secrete erythropoietin in response to hypoxia, stimulating bone marrow to produce red blood cells. In chronic kidney disease, reduced erythropoietin production leads to anemia. Recombinant erythropoietin therapy is used to correct anemia in CKD patients, improving quality of life and reducing transfusion dependence.
41. Which of the following is the main end product of protein catabolism excreted by kidneys?
• A) Creatinine
• B) Urea
• C) Uric acid
• D) Ammonia
Answer: B) Urea
Explanation: Urea is the principal nitrogenous waste product formed in the liver from protein catabolism. It is freely filtered by the glomeruli, partially reabsorbed in renal tubules, and excreted in urine. Urea clearance is sometimes used as a rough estimate of GFR but is less accurate than creatinine clearance.
42. Which test helps distinguish prerenal from renal azotemia?
• A) Serum creatinine
• B) Fractional excretion of sodium (FENa)
• C) Serum urea
• D) Urinary pH
Answer: B) Fractional excretion of sodium (FENa)
Explanation: FENa helps differentiate prerenal azotemia (<1%) from intrinsic renal damage (>2%). In prerenal states, sodium reabsorption is high to conserve volume, while in renal damage, tubular reabsorption is impaired, resulting in increased sodium excretion. This makes FENa a valuable diagnostic tool in acute kidney injury assessment.
43. Which of the following increases Blood Urea Nitrogen (BUN) disproportionately to creatinine?
• A) Liver disease
• B) High protein diet
• C) Muscle wasting
• D) Low protein intake
Answer: B) High protein diet
Explanation: A high protein diet increases urea production due to enhanced amino acid metabolism, leading to disproportionately raised BUN compared to creatinine. Gastrointestinal bleeding also raises BUN disproportionately. In contrast, liver disease reduces urea formation, lowering BUN even in the presence of renal dysfunction.
44. Which method is commonly used in laboratories for serum creatinine estimation?
• A) Jaffe’s reaction
• B) ELISA
• C) Western blot
• D) Electrophoresis
Answer: A) Jaffe’s reaction
Explanation: Jaffe’s reaction is the most commonly used method for serum creatinine estimation. In this colorimetric assay, creatinine reacts with picric acid in alkaline medium to form a red-orange complex. Despite interferences from substances like glucose and ketones, it remains widely used due to simplicity and low cost.
45. What is the normal daily excretion of creatinine in urine for an adult male?
• A) 0.2–0.5 g/day
• B) 1–2 g/day
• C) 3–4 g/day
• D) 5–6 g/day
Answer: B) 1–2 g/day
Explanation: Normal urinary creatinine excretion in adult males is around 1–2 g/day, reflecting stable muscle mass. In females, it is slightly lower (0.8–1.5 g/day). This relatively constant excretion makes creatinine useful for calculating clearance and evaluating kidney function through 24-hour urine collections.
46. Which test is most reliable for assessing concentrating ability of kidneys?
• A) Specific gravity of urine
• B) Urine osmolality
• C) Urine pH
• D) Urinary protein
Answer: B) Urine osmolality
Explanation: Urine osmolality directly measures solute concentration and is the best indicator of kidney concentrating or diluting ability. Specific gravity is less accurate as it is influenced by large molecules like glucose or proteins. In conditions like diabetes insipidus, urine osmolality remains low despite dehydration.
47. Which of the following is a marker for tubular function?
• A) Serum creatinine
• B) Urine concentrating ability
• C) Inulin clearance
• D) Serum cystatin C
Answer: B) Urine concentrating ability
Explanation: Tubular function is assessed by the kidney’s ability to concentrate or dilute urine. Impaired concentrating ability is an early sign of tubular dysfunction, as seen in chronic interstitial nephritis or early diabetic nephropathy. Serum creatinine and inulin clearance reflect GFR, not tubular performance.
48. Which test is used for estimating glomerular permeability?
• A) Proteinuria measurement
• B) PAH clearance
• C) Uric acid estimation
• D) Serum sodium
Answer: A) Proteinuria measurement
Explanation: Proteinuria is a direct measure of glomerular permeability. Normally, the glomerular basement membrane restricts passage of proteins, especially albumin. When permeability increases, proteins appear in urine. Quantifying proteinuria helps diagnose glomerulopathies and assess severity, guiding treatment and prognosis. Microalbuminuria indicates early glomerular damage, particularly in diabetes.
49. Which kidney function test is most affected by dehydration?
• A) Serum creatinine
• B) Blood urea nitrogen (BUN)
• C) Urine osmolality
• D) Uric acid
Answer: B) Blood urea nitrogen (BUN)
Explanation: BUN is highly affected by hydration status. Dehydration causes increased urea reabsorption in the renal tubules, leading to elevated BUN without true renal impairment. Creatinine is less influenced by hydration, making it more reliable for assessing kidney function in dehydration.
50. Which of the following is true regarding serum cystatin C?
• A) Derived from muscle metabolism
• B) Affected by age and muscle mass
• C) More sensitive marker of GFR than creatinine
• D) Not filtered by glomeruli
Answer: C) More sensitive marker of GFR than creatinine
Explanation: Serum cystatin C is produced by all nucleated cells and freely filtered by glomeruli. Unlike creatinine, it is independent of muscle mass, age, or diet, making it a more sensitive marker of GFR. It is particularly useful in elderly or malnourished patients where creatinine underestimates renal impairment.
51. Which is the earliest laboratory abnormality in acute kidney injury (AKI)?
• A) Proteinuria
• B) Hyperkalemia
• C) Rising serum creatinine
• D) Metabolic acidosis
Answer: C) Rising serum creatinine
Explanation: In AKI, the earliest detectable abnormality is a rise in serum creatinine due to decreased glomerular filtration. Hyperkalemia and metabolic acidosis occur later as renal failure progresses. Serial monitoring of creatinine is essential for early diagnosis and staging of acute kidney injury.
52. Which clearance test best measures renal plasma flow (RPF)?
• A) Creatinine clearance
• B) PAH clearance
• C) Urea clearance
• D) Inulin clearance
Answer: B) PAH clearance
Explanation: Para-aminohippuric acid (PAH) clearance is the gold standard for estimating effective renal plasma flow, as PAH is freely filtered and actively secreted by renal tubules, resulting in almost complete removal in one pass through the kidneys. Inulin clearance measures GFR, not RPF.
53. Which parameter is used to calculate creatinine clearance?
• A) Serum creatinine only
• B) Urine creatinine only
• C) Both urine and serum creatinine with urine volume
• D) Plasma urea and creatinine
Answer: C) Both urine and serum creatinine with urine volume
Explanation: Creatinine clearance is calculated using urine creatinine concentration, urine volume, and plasma creatinine. The formula is:
C = (U × V) / P,
where U = urine creatinine, V = urine volume/min, and P = plasma creatinine. This gives an approximate measure of GFR.
54. Which urine finding is most specific for glomerular disease?
• A) Red blood cell casts
• B) Hyaline casts
• C) White blood cell casts
• D) Granular casts
Answer: A) Red blood cell casts
Explanation: RBC casts in urine are highly specific for glomerulonephritis. They indicate bleeding within the nephron and are formed when RBCs are trapped in Tamm-Horsfall protein matrix within tubules. Hyaline casts are nonspecific, while WBC casts suggest pyelonephritis or interstitial nephritis.
55. Which test is used to assess kidney tubular secretion?
• A) Urea clearance
• B) PAH clearance
• C) Serum creatinine
• D) Inulin clearance
Answer: B) PAH clearance
Explanation: PAH is both filtered and secreted in renal tubules, making its clearance a good test for tubular secretory function. In contrast, inulin clearance tests filtration, while creatinine clearance reflects GFR. Tubular secretion tests are important in evaluating renal plasma flow and tubular health.
56. Which of the following decreases BUN disproportionately compared to creatinine?
• A) Dehydration
• B) GI bleeding
• C) Liver disease
• D) High protein diet
Answer: C) Liver disease
Explanation: In severe liver disease, urea synthesis is impaired, resulting in disproportionately low BUN compared to creatinine, despite renal dysfunction. This is important in differentiating hepatic from renal causes of altered nitrogen metabolism. In contrast, dehydration and GI bleeding increase BUN disproportionately.
57. Which parameter is commonly used in eGFR calculation formulas (like MDRD, CKD-EPI)?
• A) Serum potassium
• B) Serum creatinine
• C) Blood urea
• D) Urine sodium
Answer: B) Serum creatinine
Explanation: Estimated GFR (eGFR) equations such as MDRD and CKD-EPI rely on serum creatinine, age, sex, and race to estimate kidney function. Creatinine remains the cornerstone marker in clinical practice, though cystatin C-based equations are being increasingly used for more accuracy in certain populations.
58. What is the reference range of serum creatinine in adult females?
• A) 0.2–0.6 mg/dL
• B) 0.6–1.1 mg/dL
• C) 1.2–1.8 mg/dL
• D) 2–3 mg/dL
Answer: B) 0.6–1.1 mg/dL
Explanation: Normal serum creatinine in adult females is 0.6–1.1 mg/dL, slightly lower than in males (0.7–1.3 mg/dL) due to lesser muscle mass. Levels above the reference range suggest reduced GFR or renal impairment, but must be interpreted with hydration, diet, and muscle mass in mind.
59. Which urinary test is most sensitive for early diabetic nephropathy?
• A) Urine dipstick for protein
• B) Microalbuminuria estimation
• C) Serum creatinine
• D) BUN
Answer: B) Microalbuminuria estimation
Explanation: Microalbuminuria (30–300 mg/day) is the earliest indicator of diabetic nephropathy. Conventional dipsticks cannot detect such low levels of protein. Persistent microalbuminuria indicates early glomerular damage, necessitating intervention to prevent progression to overt proteinuria and chronic kidney disease.
60. Which factor can falsely elevate serum creatinine levels?
• A) Muscle wasting
• B) Pregnancy
• C) High meat intake
• D) Liver cirrhosis
Answer: C) High meat intake
Explanation: A diet rich in meat temporarily elevates serum creatinine due to increased intake of creatine and creatinine precursors. Other causes include certain drugs (e.g., cimetidine, trimethoprim) that reduce tubular secretion of creatinine. Conversely, muscle wasting or liver disease may lower serum creatinine levels.
61. Which is the most reliable marker of renal function in clinical practice?
• A) Serum urea
• B) Serum creatinine
• C) Serum uric acid
• D) Plasma calcium
Answer: B) Serum creatinine
Explanation: Serum creatinine is the most widely used marker of renal function because it correlates well with GFR. Urea is less reliable as it is influenced by diet, hydration, and catabolism. Though not perfect, creatinine is practical and forms the basis of eGFR calculations in clinical nephrology.
62. Which finding indicates nephrotic syndrome?
• A) Hematuria with casts
• B) Proteinuria >3.5 g/day
• C) Microalbuminuria
• D) Uric acid stones
Answer: B) Proteinuria >3.5 g/day
Explanation: Nephrotic syndrome is characterized by massive proteinuria (>3.5 g/day), hypoalbuminemia, generalized edema, and hyperlipidemia. Hematuria with casts is more typical of glomerulonephritis. Early diabetic nephropathy shows microalbuminuria. Detection of heavy proteinuria by 24-hour urine collection is key for diagnosis.
63. Which clearance test underestimates GFR due to partial reabsorption?
• A) Urea clearance
• B) Creatinine clearance
• C) Inulin clearance
• D) PAH clearance
Answer: A) Urea clearance
Explanation: Urea is partially reabsorbed in renal tubules, so its clearance underestimates GFR. Creatinine clearance slightly overestimates due to secretion, while inulin clearance is the most accurate. PAH clearance, instead, measures renal plasma flow. Urea clearance is now rarely used for renal function assessment.
64. Which test detects concentrating ability of the kidney?
• A) Specific gravity of urine
• B) Serum creatinine
• C) PAH clearance
• D) Serum electrolytes
Answer: A) Specific gravity of urine
Explanation: Specific gravity reflects urine concentration relative to water. It helps assess renal tubular function and concentrating ability. Persistent low specific gravity (isosthenuria ~1.010) suggests chronic renal failure due to inability of tubules to concentrate urine, even when plasma creatinine is not markedly raised.
65. What is the clinical significance of fractional excretion of sodium (FENa)?
• A) Differentiates pre-renal and intrinsic renal failure
• B) Detects microalbuminuria
• C) Measures GFR directly
• D) Estimates plasma osmolality
Answer: A) Differentiates pre-renal and intrinsic renal failure
Explanation: FENa helps distinguish pre-renal azotemia (<1%) from acute tubular necrosis (>2%). In pre-renal states, kidneys conserve sodium, while in tubular damage sodium is wasted. This parameter is crucial in acute kidney injury workup. It is calculated using urine and plasma sodium and creatinine values.
66. Which condition lowers serum creatinine levels?
• A) High protein diet
• B) Severe liver disease
• C) Renal obstruction
• D) Rhabdomyolysis
Answer: B) Severe liver disease
Explanation: In liver failure, reduced synthesis of creatine leads to decreased creatinine production, resulting in low serum creatinine despite renal impairment. This can mask renal dysfunction in cirrhotic patients. Conversely, rhabdomyolysis and high protein intake raise creatinine levels, while renal obstruction elevates it due to impaired excretion.
67. Which urine cast indicates chronic renal failure?
• A) RBC cast
• B) Hyaline cast
• C) Broad waxy cast
• D) Epithelial cast
Answer: C) Broad waxy cast
Explanation: Broad waxy casts are characteristic of advanced chronic kidney disease (end-stage renal disease). They form in dilated and atrophic tubules. RBC casts indicate glomerulonephritis, epithelial casts point to tubular injury, while hyaline casts are nonspecific and may appear in normal conditions.
68. Which test is preferred for detecting renal stones?
• A) Urine protein
• B) Serum creatinine
• C) Urinary calcium, oxalate, and uric acid
• D) PAH clearance
Answer: C) Urinary calcium, oxalate, and uric acid
Explanation: Stone risk evaluation requires measuring urinary excretion of calcium, oxalate, phosphate, uric acid, and citrate. Hypercalciuria and hyperoxaluria are common in calcium oxalate stones. Metabolic evaluation through 24-hour urine collection helps prevent recurrence by guiding dietary and pharmacological interventions.
69. Which test detects glomerular hyperfiltration in early diabetes?
• A) Microalbuminuria
• B) Creatinine clearance
• C) Serum creatinine
• D) Urinary glucose
Answer: B) Creatinine clearance
Explanation: In early diabetes, glomerular hyperfiltration is seen before overt nephropathy develops. Creatinine clearance or measured GFR shows increased values in this phase. Over time, microalbuminuria develops, marking early nephropathy. Serum creatinine remains normal until later. Thus, clearance studies are useful in initial stages.
70. Which urine abnormality suggests interstitial nephritis?
• A) RBC casts
• B) WBC casts with eosinophils
• C) Broad waxy casts
• D) High specific gravity
Answer: B) WBC casts with eosinophils
Explanation: WBC casts, especially with eosinophils, suggest acute interstitial nephritis, often drug-induced (e.g., antibiotics, NSAIDs). RBC casts indicate glomerular bleeding, while waxy casts suggest chronic renal failure. Specific gravity changes are nonspecific. Urine eosinophils are highly supportive in diagnosing interstitial nephritis.
71. Which test best detects early diabetic nephropathy?
• A) Serum creatinine
• B) Microalbuminuria
• C) Proteinuria >3.5 g/day
• D) Creatinine clearance
Answer: B) Microalbuminuria
Explanation: Microalbuminuria (30–300 mg/day) is the earliest sign of diabetic nephropathy. It appears before overt proteinuria or rise in serum creatinine. Screening for microalbuminuria is recommended annually in diabetics to allow early intervention with ACE inhibitors or ARBs, which slow progression to chronic kidney disease.
72. Which is the gold standard for measuring renal plasma flow (RPF)?
• A) Inulin clearance
• B) Creatinine clearance
• C) PAH clearance
• D) Urea clearance
Answer: C) PAH clearance
Explanation: Para-aminohippuric acid (PAH) clearance is used to estimate effective renal plasma flow because PAH is filtered and actively secreted, ensuring nearly complete renal excretion. Inulin measures GFR, creatinine clearance approximates GFR, and urea clearance is less accurate. Thus, PAH clearance remains the gold standard for RPF measurement.
73. Which test distinguishes glomerular from tubular proteinuria?
• A) Urine dipstick test
• B) Electrophoresis of urinary proteins
• C) Serum creatinine
• D) Creatinine clearance
Answer: B) Electrophoresis of urinary proteins
Explanation: Urine protein electrophoresis differentiates glomerular proteinuria (albumin predominant) from tubular proteinuria (low molecular weight proteins). Dipstick detects mainly albumin, but cannot differentiate origin. Serum creatinine and creatinine clearance assess renal function, not protein type. Hence, electrophoresis is vital for accurate characterization of proteinuria.
74. Which condition typically presents with hematuria and RBC casts?
• A) Nephrotic syndrome
• B) Glomerulonephritis
• C) Interstitial nephritis
• D) Acute tubular necrosis
Answer: B) Glomerulonephritis
Explanation: Glomerulonephritis is characterized by hematuria with dysmorphic RBCs and RBC casts, reflecting bleeding from damaged glomerular capillaries. Nephrotic syndrome shows massive proteinuria, interstitial nephritis has WBC casts, and acute tubular necrosis shows granular casts. Thus, RBC casts are diagnostic of glomerular pathology.
75. Which of the following decreases blood urea nitrogen (BUN) levels?
• A) Dehydration
• B) High protein diet
• C) Liver failure
• D) Gastrointestinal bleeding
Answer: C) Liver failure
Explanation: Urea is synthesized in the liver from ammonia. In liver failure, synthesis decreases, leading to reduced BUN despite possible renal dysfunction. In contrast, dehydration, GI bleeding, and high protein intake elevate BUN. Therefore, low BUN in cirrhosis may mask renal impairment.
76. Which test is most useful for detecting early renal failure?
• A) Serum creatinine
• B) Estimated GFR (eGFR)
• C) Serum uric acid
• D) Urine specific gravity
Answer: B) Estimated GFR (eGFR)
Explanation: eGFR, calculated using creatinine-based formulas (MDRD, CKD-EPI), is more sensitive than serum creatinine alone for detecting early renal failure. Creatinine levels may remain normal until significant nephron loss occurs. eGFR considers age, sex, and race, improving detection of mild renal dysfunction.
77. What is the diagnostic test for Fanconi syndrome?
• A) Serum creatinine
• B) Urinary amino acids, glucose, phosphate
• C) Inulin clearance
• D) PAH clearance
Answer: B) Urinary amino acids, glucose, phosphate
Explanation: Fanconi syndrome results from proximal tubular dysfunction, leading to generalized reabsorption defects. This causes glycosuria, aminoaciduria, phosphaturia, and bicarbonaturia despite normal plasma levels. Detecting these solutes in urine confirms the diagnosis. Creatinine clearance and inulin clearance reflect GFR, not tubular function.
78. Which test is best for monitoring progression of chronic kidney disease (CKD)?
• A) Serum creatinine trend
• B) Estimated GFR
• C) BUN alone
• D) Urinary glucose
Answer: B) Estimated GFR
Explanation: eGFR is the preferred parameter to monitor CKD progression because it reflects renal function decline more reliably than serum creatinine. Staging of CKD (G1–G5) is based on eGFR. BUN is influenced by diet and hydration, while urinary glucose is unrelated to CKD progression.
79. Which abnormality is seen in renal tubular acidosis (RTA)?
• A) Hyperkalemia and metabolic alkalosis
• B) Hypokalemia and metabolic acidosis
• C) Hypernatremia and respiratory alkalosis
• D) Hypocalcemia and respiratory acidosis
Answer: B) Hypokalemia and metabolic acidosis
Explanation: RTA is characterized by defective tubular acid secretion or bicarbonate reabsorption, leading to metabolic acidosis with normal anion gap. Hypokalemia is common in distal and proximal RTA. Hyperkalemia may occur in type 4 RTA. Other options do not match the typical biochemical pattern of RTA.
80. Which laboratory parameter is most affected by high-protein diet?
• A) Serum calcium
• B) Serum creatinine
• C) Blood urea nitrogen (BUN)
• D) Serum potassium
Answer: C) Blood urea nitrogen (BUN)
Explanation: High-protein intake increases amino acid metabolism, producing more urea, thus elevating BUN levels. Serum creatinine is influenced mainly by muscle mass, not diet. Serum calcium and potassium are not significantly affected by dietary protein intake. Hence, BUN is the most diet-sensitive renal function parameter.
81. Which urine test is most sensitive for detecting small amounts of proteinuria?
• A) Heat coagulation test
• B) Dipstick test
• C) Sulfosalicylic acid test
• D) Benedict’s test
Answer: C) Sulfosalicylic acid test
Explanation: The sulfosalicylic acid test precipitates all proteins, including globulins and Bence Jones proteins, making it more sensitive than dipstick, which primarily detects albumin. Heat coagulation detects mainly albumin, while Benedict’s detects glucose, not protein. Thus, sulfosalicylic acid test is preferred for trace proteinuria detection.
82. What is the normal albumin-to-creatinine ratio (ACR) in urine?
• A) <10 mg/g
• B) <30 mg/g
• C) <100 mg/g
• D) <300 mg/g
Answer: B) <30 mg/g
Explanation: A urine ACR <30 mg/g is normal. Microalbuminuria is 30–300 mg/g, while macroalbuminuria is >300 mg/g. ACR provides a reliable estimate, correcting for urine concentration by relating albumin excretion to creatinine. It is widely used for screening kidney disease, especially in diabetics and hypertensives.
83. Which of the following causes prerenal azotemia?
• A) Acute tubular necrosis
• B) Renal artery stenosis
• C) Chronic glomerulonephritis
• D) Polycystic kidney disease
Answer: B) Renal artery stenosis
Explanation: Prerenal azotemia arises from decreased renal perfusion without intrinsic renal damage. Causes include hypovolemia, shock, and renal artery stenosis. In contrast, acute tubular necrosis and glomerulonephritis are intrinsic renal causes, while polycystic kidney disease is a chronic structural renal disorder.
84. What is the normal daily creatinine excretion in urine?
• A) 200–500 mg
• B) 500–1000 mg
• C) 1–2 g
• D) 15–20 g
Answer: C) 1–2 g
Explanation: Normal daily urinary creatinine excretion is 1–2 g, depending on muscle mass and diet. It remains relatively constant in an individual, which is why creatinine clearance is a reliable measure of GFR. Lower values may indicate muscle wasting, while higher values occur in muscular individuals.
85. Which test best evaluates concentrating ability of kidneys?
• A) Water deprivation test
• B) PAH clearance
• C) Serum creatinine
• D) Creatinine clearance
Answer: A) Water deprivation test
Explanation: The water deprivation test assesses renal concentrating ability by measuring urine osmolality after fluid restriction. In diabetes insipidus, urine remains dilute despite dehydration. Creatinine clearance measures GFR, PAH clearance measures RPF, and serum creatinine reflects renal function but not concentrating ability.
86. Which urinary cast indicates chronic renal failure?
• A) Hyaline cast
• B) Granular cast
• C) Waxy cast
• D) Fatty cast
Answer: C) Waxy cast
Explanation: Waxy casts are seen in chronic renal failure and advanced tubular atrophy, indicating long-standing renal disease. Hyaline casts may be normal, granular casts indicate acute tubular necrosis, and fatty casts are typical of nephrotic syndrome. Thus, waxy casts reflect end-stage renal disease.
87. Which of the following is NOT a feature of nephrotic syndrome?
• A) Proteinuria >3.5 g/day
• B) Hypoalbuminemia
• C) Hyperlipidemia
• D) Hematuria with RBC casts
Answer: D) Hematuria with RBC casts
Explanation: Nephrotic syndrome presents with massive proteinuria, hypoalbuminemia, hyperlipidemia, and edema. Hematuria with RBC casts is typical of nephritic syndrome, not nephrotic syndrome. This distinction is important in differentiating glomerular pathologies clinically and biochemically.
88. Which electrolyte disturbance is common in chronic kidney disease (CKD)?
• A) Hypokalemia
• B) Hyperkalemia
• C) Hyponatremia
• D) Hypocalcemia
Answer: B) Hyperkalemia
Explanation: In CKD, impaired renal excretion leads to hyperkalemia, which can cause life-threatening cardiac arrhythmias. Hypocalcemia and hyperphosphatemia also occur due to decreased vitamin D activation. Hypokalemia is more common in RTA or diuretic therapy, not CKD.
89. Which test is used to measure glomerular permeability to proteins?
• A) Urine dipstick
• B) Selectivity index
• C) Sulfosalicylic acid test
• D) Urine microscopy
Answer: B) Selectivity index
Explanation: The selectivity index is calculated by comparing clearance of different plasma proteins. A low index indicates selective albuminuria (minimal change disease), while a high index indicates non-selective proteinuria (focal segmental or membranous GN). It helps assess severity of glomerular damage.
90. Which finding suggests intrinsic renal failure rather than prerenal azotemia?
• A) BUN:Creatinine ratio >20:1
• B) Fractional excretion of sodium (FENa) >2%
• C) Urine osmolality >500 mOsm/kg
• D) Rapid fall in BUN after hydration
Answer: B) Fractional excretion of sodium (FENa) >2%
Explanation: In intrinsic renal failure like acute tubular necrosis, kidneys lose ability to conserve sodium, so FENa >2%. In prerenal azotemia, FENa <1% due to intact tubular reabsorption. BUN:Creatinine >20:1 suggests prerenal, while urine osmolality >500 mOsm/kg favors prerenal causes.
91. Which urine test is diagnostic for multiple myeloma?
• A) Heat coagulation test
• B) Bence Jones protein test
• C) Benedict’s test
• D) Dipstick
Answer: B) Bence Jones protein test
Explanation: Bence Jones proteins are monoclonal light chains excreted in urine of multiple myeloma patients. They precipitate on heating at 40–60°C and redissolve on boiling. Dipstick may miss them, as it mainly detects albumin. Hence, special tests for Bence Jones protein are diagnostic.
92. Which enzyme level rises earliest in obstructive nephropathy?
• A) Serum creatine kinase
• B) Serum alkaline phosphatase
• C) Serum N-acetyl-β-glucosaminidase (NAG)
• D) Serum lactate dehydrogenase
Answer: C) Serum N-acetyl-β-glucosaminidase (NAG)
Explanation: NAG is a lysosomal enzyme released from proximal tubular cells. Its rise in urine is an early marker of tubular injury, including obstructive nephropathy and drug-induced nephrotoxicity. Other enzymes are not specific for renal tubular damage.
93. Which marker is most specific for renal function?
• A) BUN
• B) Serum creatinine
• C) Cystatin C
• D) Serum uric acid
Answer: C) Cystatin C
Explanation: Cystatin C, a low-molecular-weight protein, is freely filtered at the glomerulus and not affected by muscle mass or diet, making it a sensitive and specific marker of GFR. BUN and creatinine are widely used but influenced by non-renal factors. Uric acid reflects purine metabolism, not renal function.
94. What is the normal urine protein excretion in 24 hours?
• A) <30 mg
• B) <150 mg
• C) <300 mg
• D) <500 mg
Answer: B) <150 mg
Explanation: Normal urine protein excretion is <150 mg/day, mostly Tamm-Horsfall protein. Microalbuminuria is 30–300 mg/day, while overt proteinuria is >300 mg/day. Persistent elevation suggests renal pathology and needs further evaluation.
95. Which test differentiates acute tubular necrosis (ATN) from prerenal azotemia?
• A) Serum creatinine
• B) Urine osmolality
• C) Fractional excretion of sodium (FENa)
• D) Serum potassium
Answer: C) Fractional excretion of sodium (FENa)
Explanation: FENa is <1% in prerenal azotemia due to intact sodium reabsorption, but >2% in ATN due to tubular dysfunction. Serum creatinine and potassium rise in both conditions, while urine osmolality is low in ATN but high in prerenal, less specific than FENa.
96. Which hormone is reduced in chronic kidney disease?
• A) Insulin
• B) Erythropoietin
• C) Cortisol
• D) Aldosterone
Answer: B) Erythropoietin
Explanation: CKD leads to decreased erythropoietin production by damaged peritubular interstitial cells, resulting in normocytic normochromic anemia. Insulin metabolism may decrease, but secretion is intact. Cortisol and aldosterone are unaffected primarily by CKD.
97. Which urinary finding is specific for nephrotic syndrome?
• A) RBC casts
• B) WBC casts
• C) Fatty casts
• D) Waxy casts
Answer: C) Fatty casts
Explanation: Fatty casts and “Maltese cross” appearance under polarized light are hallmarks of nephrotic syndrome. They result from lipiduria due to increased lipoprotein synthesis and leakage. RBC casts are nephritic, WBC casts indicate pyelonephritis, and waxy casts suggest chronic renal failure.
98. Which of the following is NOT a marker of tubular function?
• A) Urinary concentrating ability
• B) Acidification test
• C) Creatinine clearance
• D) Excretion of glucose
Answer: C) Creatinine clearance
Explanation: Creatinine clearance reflects GFR, a glomerular function test. Tubular function tests include urine concentrating ability, acidification (RTA detection), and abnormal excretion of glucose, phosphate, and amino acids (Fanconi syndrome).
99. Which electrolyte imbalance is most dangerous in acute kidney injury (AKI)?
• A) Hypokalemia
• B) Hyperkalemia
• C) Hyponatremia
• D) Hypocalcemia
Answer: B) Hyperkalemia
Explanation: Hyperkalemia is the most life-threatening complication of AKI due to impaired excretion. It predisposes to cardiac arrhythmias, requiring urgent management with calcium gluconate, insulin-glucose infusion, or dialysis. Hyponatremia and hypocalcemia occur but are less acutely dangerous.
100. Which of the following is the earliest abnormality in diabetic nephropathy?
• A) Proteinuria >3.5 g/day
• B) Microalbuminuria
• C) Decline in GFR
• D) Hypertension
Answer: B) Microalbuminuria
Explanation: Microalbuminuria (30–300 mg/day) is the first detectable marker of diabetic nephropathy. It precedes overt proteinuria and decline in GFR. Hypertension usually develops later as renal damage progresses. Early detection allows intervention to delay progression to chronic kidney disease.