Master Internal Medicine
for USMLE Step 2 CK

Core Concepts

Internal Medicine on USMLE Step 2 CK emphasizes a structured approach to common adult diseases, focusing on differential diagnosis, initial workup, and first-line management. Key principles include recognizing life-threatening conditions, understanding pathophysiology, and applying evidence-based medicine. Many questions test the ability to interpret lab results, imaging, and patient history to arrive at the most likely diagnosis and appropriate intervention. Always consider patient comorbidities and drug interactions.

Clinical Presentation

• Cardiology: Chest pain (anginal vs. pleuritic vs. positional), dyspnea (exertional, orthopnea, PND), palpitations, syncope, peripheral edema.
• Pulmonology: Cough (acute vs. chronic, productive vs. dry), dyspnea (acute vs. chronic, inspiratory vs. expiratory), hemoptysis, wheezing, pleuritic chest pain.
• Gastroenterology: Abdominal pain (location, character, radiation), nausea/vomiting, diarrhea/constipation, GI bleeding (hematemesis, melena, hematochezia), jaundice, dysphagia.
• Nephrology: Edema, changes in urine output, flank pain, hematuria, polyuria/polydipsia, symptoms of uremia (fatigue, pruritus, altered mental status).
• Endocrinology: Weight changes (gain/loss), polyuria/polydipsia, heat/cold intolerance, fatigue, changes in skin/hair, mood disturbances.
• Rheumatology: Joint pain/swelling (monoarticular vs. polyarticular, inflammatory vs. mechanical), morning stiffness, rash, oral ulcers, photosensitivity, Raynaud's phenomenon.
• Hematology/Oncology: Fatigue, pallor, easy bruising/bleeding, recurrent infections, unexplained weight loss, night sweats, lymphadenopathy.
• Infectious Disease: Fever, chills, myalgias, localized pain, rash, lymphadenopathy.

Diagnosis (Gold Standard)

Often involves a combination of clinical picture, labs, and imaging.

• MI: ECG changes (ST elevation/depression, T-wave inversion) + cardiac troponins.
• Heart Failure: Echocardiogram (EF, ventricular function).
• Pulmonary Embolism (PE): CT Pulmonary Angiography (CT-PA).
• COPD/Asthma: Spirometry (FEV1/FVC ratio).
• Peptic Ulcer Disease (PUD): Upper Endoscopy.
• Acute Pancreatitis: Lipase >3x ULN + characteristic abdominal pain.
• IBD (Crohn's/UC): Colonoscopy with biopsy.
• Chronic Kidney Disease (CKD): eGFR <60 for >3 months + albuminuria.
• Diabetes Mellitus: HbA1c ≥6.5% OR FBG ≥126 mg/dL OR 2hr OGTT ≥200 mg/dL OR random BG ≥200 mg/dL with symptoms.
• Hypothyroidism: Elevated TSH, low Free T4.
• Gout: Synovial fluid analysis showing negatively birefringent needle-shaped crystals.
• Lupus (SLE): Clinical criteria + positive ANA (highly sensitive).
• Sepsis: Suspected infection + new organ dysfunction (SOFA score).

Management (First Line)

• MI (STEMI): Aspirin, P2Y12 inhibitor, nitrates, statin, O2, morphine + prompt reperfusion (PCI within 90-120 min or fibrinolytics).
• Heart Failure (HFrEF): ACEi/ARB, beta-blocker, aldosterone antagonist, SGLT2 inhibitor. Loop diuretics for symptom relief.
• Hypertension: Lifestyle modifications. First-line agents: Thiazide diuretics, ACEi/ARB, CCB.
• PE: Anticoagulation (heparin products, then oral DOACs). Thrombolysis for massive PE with hemodynamic instability.
• COPD Exacerbation: SABA, systemic corticosteroids, antibiotics if signs of bacterial infection.
• Asthma Exacerbation: SABA, systemic corticosteroids.
• PUD: PPI. H. pylori eradication (PPI + 2-3 antibiotics) if present.
• Acute Pancreatitis: Aggressive IV fluids, pain control, NPO.
• Diabetic Ketoacidosis (DKA): IV fluids, insulin drip, potassium replacement.
• Hypothyroidism: Levothyroxine.
• Gout Flare: NSAIDs (e.g., indomethacin), colchicine, or oral corticosteroids.
• Septic Shock: IV fluid resuscitation (30ml/kg crystalloids), broad-spectrum antibiotics (within 1 hour), vasopressors (norepinephrine) if hypotension persists.
• Community-Acquired Pneumonia (CAP): Macrolide or doxycycline (outpatient); ceftriaxone + azithromycin/doxycycline or fluoroquinolone (inpatient).

Exam Red Flags