Nephrology:
Nephrology Quick Review for USMLE Step 2 CK
Nephrology is a high-yield topic for USMLE Step 2 CK, covering disorders related to the kidneys, electrolytes, acid-base balance, and renal physiology. Questions often test your ability to diagnose and manage common renal diseases, interpret lab values, and recognize urgent nephrology conditions.In this quick review, we’ll cover the key nephrology topics frequently tested on Step 2 CK to help you maximize your score.
1. Acute Kidney Injury (AKI)
Acute Kidney Injury (AKI) is a sudden decline in renal function, classified into three major types:
🔹 Prerenal AKI (Most Common Type)Causes: Hypovolemia (dehydration, hemorrhage), heart failure, renal artery stenosis, NSAIDs, ACE inhibitors
Labs:
✔ BUN/Creatinine Ratio > 20:1
✔ Low Urine Sodium (<20 mEq/L)
✔ Fractional Excretion of Sodium (FeNa) <1%Treatment: Fluids, correct underlying cause
🔹 Intrinsic AKICauses:
✔ Acute Tubular Necrosis (ATN) – Ischemia, nephrotoxins (aminoglycosides, contrast)
✔ Glomerulonephritis – Hematuria, RBC casts
✔ Acute Interstitial Nephritis (AIN) – NSAIDs, penicillins, sulfa drugs
Labs:
✔ BUN/Creatinine Ratio ~10-15:1
✔ Urine Sodium >40 mEq/L, FeNa >2%Treatment: Address underlying cause, supportive care
🔹 Postrenal AKICauses: Urinary obstruction (BPH, kidney stones, tumors)Diagnosis: Renal ultrasound showing hydronephrosisTreatment: Relieve obstruction (foley catheter, surgery)
2. Chronic Kidney Disease (CKD)
Chronic Kidney Disease (CKD) is a progressive loss of renal function (GFR <60 mL/min for >3 months).Stages of CKD:
✔ Stage 1: Normal GFR (>90) but kidney damage
✔ Stage 2-3: Mild to moderate GFR decline
✔ Stage 4: GFR <30 (severe CKD)
✔ Stage 5: GFR <15 (End-Stage Renal Disease, requires dialysis or transplant)
Complications:
✔ Metabolic Acidosis (Normal AG acidosis) – Treat with bicarbonate
✔ Hyperkalemia – Treat with calcium gluconate, insulin + glucose, kayexalate
✔ Anemia of CKD – Treat with erythropoietin if Hb <10
✔ Bone Disease – Low calcium, high phosphate, treat with phosphate binders
3. Glomerular Diseases (Nephritic vs. Nephrotic Syndrome)
🔹 Nephritic Syndrome (Inflammatory)
Key Features:
✔ Hematuria, RBC casts
✔ Hypertension
✔ Oliguria
✔ Mild proteinuria
Common Causes:
Post-Streptococcal Glomerulonephritis (PSGN) – Children, post-infection, low C3IgA Nephropathy (Berger's Disease) – Young adults, post-URI, normal C3Lupus Nephritis – Positive ANA, anti-dsDNA
Management: Supportive care, steroids for severe cases
🔹 Nephrotic Syndrome (Protein Losing)
Key Features:
✔ Massive Proteinuria (>3.5 g/day)
✔ Hypoalbuminemia, Edema
✔ Hyperlipidemia
Common Causes:
Minimal Change Disease (MCD) – Most common in children, responds to steroidsFocal Segmental Glomerulosclerosis (FSGS) – Common in African Americans, associated with HIV, heroin useMembranous Nephropathy – Most common in adults, associated with Hepatitis B, malignancy
Management:
✔ ACE inhibitors to reduce proteinuria
✔ Diuretics for edema
✔ Steroids/Immunosuppressants (for some cases)
4. Electrolyte Disorders
🔹 Hyperkalemia (K+ >5.5 mEq/L)Causes: CKD, acidosis, K-sparing diuretics, ACE inhibitors
ECG Findings: Peaked T waves → Widened QRS → Sine waves → Risk of cardiac arrest
Treatment:
✔ Calcium gluconate (stabilizes cardiac membrane)
✔ Insulin + glucose, beta-agonists (shift K+ intracellularly)
✔ Kayexalate, loop diuretics, dialysis (eliminate K+)
🔹 Hyponatremia (Na+ <135 mEq/L)Causes: SIADH, heart failure, cirrhosis, excessive fluids
Symptoms: Confusion, seizures, coma
Management:✔ Mild (Asymptomatic): Fluid restriction
✔ Moderate (Confusion): Hypertonic saline (if symptomatic)
✔ Severe (Seizures): 3% NaCl infusion slowly to avoid central pontine myelinolysis
5. Acid-Base Disorders
🔹 Metabolic Acidosis
Normal Anion Gap (Hyperchloremic): Diarrhea, RTA
High Anion Gap: MUDPILES (Methanol, Uremia, DKA, Paraldehyde, Iron/INH, Lactic acidosis, Ethylene glycol, Salicylates)
Treatment: Correct underlying cause, bicarbonate if severe
🔹 Metabolic AlkalosisCauses: Vomiting, diuretics, hyperaldosteronism
Treatment: Fluids, correct potassium deficit
Key Takeaways for Step 2 CK
✅ Understand AKI vs. CKD differentiation and key lab values✅ Know the differences between nephritic and nephrotic syndromes✅ Memorize high-yield electrolyte disturbances and their ECG findings✅ Be comfortable managing acid-base disorders with ABG interpretation✅ Recognize hypertensive emergency in CKD patients and know the first-line management
How IMG Rotations Can Help You Prepare for your residency match:
At IMG Rotations, we provide:
✔ Hands-on U.S. Clinical Experience (USCE) to strengthen your residency application
✔ Clinical exposure to nephrology cases in real hospital settings
✔ Expert guidance and mentorship from board-certified U.S. physicians