Source / episode info

• **Episode:**394
• **Title:**Divine Intervention Episode 394 – USMLE Step 2CK/3 Rapid Review Series 76
• **Published:**2022-06-04
• Source:Episode page

One-liner

This episode reviews critical board topics including methanol/ethylene glycol poisoning workups, the diagnosis and treatment of C. difficile colitis, acute interstitial nephritis (AIN), differentiating central versus nephrogenic diabetes insipidus, and distinguishing between von Willebrand disease and Bernard-Soulier syndrome.

High-yield summary

• Methanol Poisoning: Clinical suspicion is raised by optic disc hyperemia or kidney injury; treatment involves Formepizole to inhibit alcohol dehydrogenase and prevent the formation of toxic metabolites (formic acid, formaldehyde).
• C. difficile Colitis: Characterized by pseudomembranous colitis and can cause both watery and bloody diarrhea; first-line empirical therapy includes oral Vancomycin or Fidaxomicin.
• Acute Interstitial Nephritis (AIN): A classic triad is fever, rash, and pyuria; it has a strong association with recent antibiotic use (e.g., cephalosporins).
• Central vs. Nephrogenic DI: Central DI results from ADH deficiency and is treated with an ADH analog (Desmopressin); Nephrogenic DI involves renal resistance to ADH and can be caused by lithium, hypercalcemia, or tetracyclines.
• Bleeding Disorders: In von Willebrand disease (vWD), the PTT is prolonged due to impaired Factor VIII half-life; in Bernard-Soulier syndrome (BSS), the defect lies in platelet adhesion via GP1b.

Learning objectives

• Differentiate the toxic metabolites and clinical presentation of methanol versus ethylene glycol poisoning.
• Identify the appropriate first-line antibiotics for C. difficile colitis based on resistance patterns.
• Recognize the classic triad and common triggers associated with Acute Interstitial Nephritis (AIN).
• Systematically differentiate between central and nephrogenic diabetes insipidus using fluid/electrolyte analysis and diagnostic testing.
• Distinguish the underlying pathophysiology and laboratory findings of von Willebrand disease versus Bernard-Soulier syndrome.

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