Source / episode info
- **Episode:**124
- **Title:**Divine Intervention Episode 124 – ABIM/Medicine ITE/USMLE Step 3 Review Series 9 (Nephrology)
- **Published:**2019-07-20
- Source:Episode page
One-liner
This episode provides a comprehensive review of Acute Kidney Injury (AKI), detailing the pathophysiology and diagnostic differentiation between pre-renal (hypoperfusion), intrinsic renal (tubular/interstitial damage), and post-renal causes using specific lab values and clinical signs.
High-yield summary
- Pre-renal AKI: Caused by decreased effective arterial blood volume (e.g., hemorrhage, severe gastroenteritis, CHF exacerbation, nephrotic syndrome). The body compensates via RAAS/ADH activation, leading to low urine sodium (<20 mEq/L), low FeNa (<1%), and high urine osmolality (>500 mOsm/kg).
- Intrinsic AKI: Most common type; involves damage to the glomerulus (glomerulonephritis), tubules (Acute Tubular Necrosis - ATN), or interstitium (AIN). Causes include nephrotoxins, rhabdomyolysis, and contrast media.
- AKI Differentiation: The key diagnostic markers are quantitative: Pre-renal AKI typically has a BUN/Cr ratio > 20:1; Intrinsic AKI often has a FeNa > 2%.
- Nephrotoxic Agents: Key drugs to remember include Aminoglycosides (Gentamicin), Vancomycin, Cisplatin, and Ethylene Glycol.
- Classic Presentations: Acute Interstitial Nephritis (AIN) classically presents with the triad of fever, rash, and eosinophilia; Rhabdomyolysis can cause hyperkalemia and elevated CK/myoglobinuria.
Learning objectives
- Differentiate between pre-renal, intrinsic (ATN), and post-renal causes of AKI using clinical history and laboratory values.
- Identify common nephrotoxins and their associated mechanisms of injury.
- Recognize the classic signs and symptoms associated with specific renal pathologies (e.g., AIN triad, rhabdomyolysis findings).
- Understand the compensatory physiological responses (RAAS/ADH) in hypoperfusion states.
- Determine appropriate management strategies for AKI based on etiology (e.g., fluid resuscitation vs. dialysis).
Board exam buzzwords