Nephrology — USMLE Step 3 Practice
Nephrology on USMLE Step 3 covers acute kidney injury, chronic kidney disease, glomerulonephritis, electrolyte disorders, and acid-base physiology. Interpreting urinalysis and managing dialysis indications are high-yield topics.
Frequently Asked Questions
What are the indications for emergent dialysis on USMLE Step 3?
The AEIOU mnemonic: Acidosis (pH <7.1 refractory to treatment), Electrolyte abnormalities (hyperkalemia with EKG changes), Intoxication (methanol, ethylene glycol, lithium, salicylates), Overload (fluid overload refractory to diuretics), Uremia symptoms (pericarditis, encephalopathy, bleeding).
How do you differentiate pre-renal from intrinsic AKI?
Pre-renal AKI: BUN/Cr ratio >20, FENa <1%, urine specific gravity >1.020, bland urinalysis. Intrinsic AKI (ATN): BUN/Cr ratio <20, FENa >2%, urine specific gravity ~1.010, muddy brown granular casts on urinalysis. In pre-renal, creatinine normalizes with IV fluids.
What is the Step 3 approach to hyperkalemia with EKG changes?
Peaked T waves → PR prolongation → wide QRS → sine wave pattern → VF. Immediate treatment: calcium gluconate IV (membrane stabilization), then insulin + dextrose (shift K+ intracellularly), sodium bicarbonate if acidotic. Kayexalate or patiromer for elimination; dialysis if severe or refractory.
How do you work up nephrotic syndrome?
Nephrotic syndrome (proteinuria >3.5g/day, hypoalbuminemia, edema, hyperlipidemia) in adults requires renal biopsy to identify the cause. Most common causes: membranous nephropathy (primary or secondary to cancer/drugs/lupus), focal segmental glomerulosclerosis, minimal change disease (adults: rule out lymphoma).
What are the CKD complications managed on Step 3?
CKD complications: hyperphosphatemia (phosphate binders — calcium acetate), secondary hyperparathyroidism (calcitriol or cinacalcet), anemia (EPO + iron supplementation if ferritin <200 or TSAT <20%), metabolic acidosis (sodium bicarbonate when HCO3 <22), and hyperkalemia (dietary restriction + loop diuretics).
Related Articles
- High-Yield Nephrology for USMLE Step 3: AKI, CKD, and Electrolyte Disorders
Master nephrology for USMLE Step 3 — AKI differential, CKD complications, electrolyte emergencies, acid-base interpretation, and dialysis indications.
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