Internal Medicine Exam Acute Kidney Injury 3 — Questions and Answers
Question 1: A 45-year-old woman undergoing coronary angiography receives iodinated contrast. Her baseline creatinine is 1.6 mg/dL. Which intervention has the strongest evidence for preventing contrast-induced AKI?
- N-acetylcysteine administration
- Isotonic saline hydration before and after the procedure (Correct answer)
- Sodium bicarbonate infusion
- Furosemide administration before contrast
Correct answer: Isotonic saline hydration before and after the procedure
Isotonic saline (0.9% NaCl) pre- and post-procedure hydration remains the best-established intervention for preventing contrast-induced nephropathy.
Question 2: A patient with AKI has serum potassium of 6.8 mEq/L. ECG shows peaked T waves, widened QRS, and a sine wave pattern. What is the FIRST treatment to administer?
- Sodium bicarbonate IV
- Calcium gluconate IV (Correct answer)
- Insulin plus dextrose IV
- Sodium polystyrene sulfonate (Kayexalate)
Correct answer: Calcium gluconate IV
Calcium gluconate IV is given first to stabilize the cardiac membrane and protect against life-threatening arrhythmias, though it does not lower serum potassium.
Question 3: Which of the following best distinguishes hepatorenal syndrome (HRS) from prerenal AKI in a cirrhotic patient?
- BUN/creatinine ratio >20
- Failure to respond to albumin and discontinuation of diuretics (Correct answer)
- Urine sodium <20 mEq/L
- Oliguria with concentrated urine
Correct answer: Failure to respond to albumin and discontinuation of diuretics
HRS is diagnosed when AKI in cirrhosis fails to resolve after 48 hours of volume resuscitation with albumin (1 g/kg/day) and withdrawal of diuretics and nephrotoxins.
Question 4: A 30-year-old marathon runner collapses near the finish line. Labs show creatinine 4.2 mg/dL, CK 85,000 U/L, urine dipstick positive for blood but no RBCs on microscopy. What is the pathophysiology of AKI in this case?
- Heat stroke causing glomerulonephritis
- Myoglobinuria causing tubular injury and cast obstruction (Correct answer)
- NSAIDs taken pre-race causing interstitial nephritis
- Dehydration alone causing prerenal AKI
Correct answer: Myoglobinuria causing tubular injury and cast obstruction
Rhabdomyolysis releases myoglobin, which causes direct tubular toxicity, tubular obstruction by casts, and renal vasoconstriction, leading to AKI.
Question 5: Which biomarker has emerged as an early indicator of AKI that rises before serum creatinine?
- Serum cystatin C
- NGAL (neutrophil gelatinase-associated lipocalin) (Correct answer)
- BUN
- Serum phosphorus
Correct answer: NGAL (neutrophil gelatinase-associated lipocalin)
NGAL is released rapidly from injured tubular cells and rises within 2 hours of AKI, making it a sensitive early biomarker before creatinine elevation occurs.
Question 6: A 60-year-old woman develops AKI after a hip replacement. She has been on ibuprofen for pain and started lisinopril 1 month ago for hypertension. Her creatinine is 2.9 mg/dL, urine output is 30 mL/hour, and BP is 95/60 mmHg. What is the best initial management?
- Start dialysis immediately
- Discontinue NSAID and ACE inhibitor, administer IV fluids (Correct answer)
- Double the lisinopril dose
- Start vasopressors
Correct answer: Discontinue NSAID and ACE inhibitor, administer IV fluids
Discontinuing nephrotoxic agents (NSAIDs block prostaglandin-mediated afferent vasodilation; ACE inhibitors blunt efferent constriction) and restoring volume is the correct first step.
Question 7: In AKI due to tumor lysis syndrome, which metabolic abnormalities are most characteristic?
- Hyperuricemia, hyperphosphatemia, hypocalcemia, hyperkalemia (Correct answer)
- Hyponatremia, hypocalcemia, hypophosphatemia, hypokalemia
- Metabolic alkalosis with hypokalemia
- Hypercalcemia and hypernatremia
Correct answer: Hyperuricemia, hyperphosphatemia, hypocalcemia, hyperkalemia
Tumor lysis syndrome causes massive release of intracellular contents, producing hyperuricemia, hyperphosphatemia, hypocalcemia (from phosphate binding calcium), and hyperkalemia.
Internal Medicine Exam Acute Kidney Injury 3
A 45-year-old woman undergoing coronary angiography receives iodinated contrast.
Her baseline creatinine is 1.6 mg/dL.
Which intervention has the strongest evidence for preventing contrast-induced AKI?