Source / episode info
- **Episode:**320
- **Title:**Divine Intervention Episode 320 – USMLE Step 2CK Rapid Review Series 59 (and 20hr 2CK/3 course reminder 6/18-19).
- **Published:**2021-06-14
- Source:Episode page
One-liner
This episode provides a rapid review of high-yield topics including the differentiation between Primary Biliary Cholangitis (PBC) and Primary Sclerosing Cholangitis (PSC), the systemic manifestations and treatment mechanism for Multiple Myeloma, and the complex physiology governing volume depletion and cardiac shunts.
High-yield summary
- PBC vs PSC: PBC is typically associated with anti-mitochondrial antibodies (AMA) and affects only the intra-hepatic bile ducts; PSC involves both intra and extra-hepatic ducts.
- Multiple Myeloma (MM): The classic mnemonic for MM findings is CRAB: Calcium elevation (hypercalcemia), Renal failure (due to light chain deposition/amyloidosis), Anemia, and Bone pain (osteolytic lesions).
- MM Treatment: Bortezomib, a proteasome inhibitor, is the drug of choice because it prevents the degradation of pro-apoptotic proteins, allowing myeloma cells to undergo apoptosis.
- Hypovolemia Physiology: Volume depletion activates the RAAS system, leading to increased aldosterone secretion. This causes sodium reabsorption and potassium wasting (hypokalemia) and proton excretion (metabolic alkalosis).
- BUN/Cr Ratio: In hypovolemic states, the BUN rises faster than creatinine because of enhanced tubular handling driven by ADH/aldosterone effects on urea/sodium balance.
- Cardiac Shunts: A large Patent Ductus Arteriosus (PDA) causes a left-to-right shunt; chronic hypoxia (e.g., from severe pulmonary disease) can reverse this to a right-to-left, cyanotic shunt.
Learning objectives
- Differentiate the pathophysiology and management of PBC versus PSC.
- Recognize the clinical constellation (CRAB) associated with Multiple Myeloma and understand the mechanism of bortezomib.
- Analyze electrolyte disturbances in hypovolemic states, linking them to RAAS activation.
- Interpret findings related to cardiac shunts and chronic hypoxia.
- Apply knowledge of biliary drainage procedures for malignant obstruction.