During a postmortem examination of a 68-year-old woman who died of acute renal failure, the pathologist observes acute tubular necrosis (ATN) with loss of brush border and cellular debris in the tubular lumen. Which of the following is the most common cause of acute tubular necrosis in India?

Explanation

## Most Common Cause of Acute Tubular Necrosis (ATN) **Key Point:** Sepsis with hypotension (ischemic ATN) is the most common cause of acute tubular necrosis in India and globally, accounting for >50% of all ATN cases. ### Pathophysiology of Ischemic ATN 1. **Hypotension and renal hypoperfusion** → reduced glomerular filtration pressure 2. **Tubular epithelial cell ischemia** → ATP depletion 3. **Loss of Na^+^/K^+^ ATPase function** → cell swelling and detachment 4. **Brush border loss** → impaired reabsorption and increased intraluminal pressure 5. **Cellular debris accumulation** → tubular obstruction and back-leak of filtrate 6. **Irreversible injury** if ischemia persists >4–6 hours ### Two Types of ATN | Feature | Ischemic ATN | Nephrotoxic ATN | |---------|--------------|------------------| | **Most common cause** | Sepsis, shock, major surgery | Aminoglycosides, contrast, myoglobin | | **Frequency** | ~50% of ATN | ~35% of ATN | | **Prognosis** | Mortality 40–50% | Mortality 10–20% | | **Mechanism** | Hypoperfusion → cell death | Direct tubular toxicity | | **Recovery** | Slower (weeks) | Faster (days) | **Clinical Pearl:** In Indian hospitals, sepsis-related ATN is more common than in developed nations due to higher rates of infection, delayed presentation, and limited ICU resources. ### Epidemiology in India **High-Yield:** Sepsis and septic shock are the leading causes of acute kidney injury (AKI) and ATN in Indian tertiary care centers. Sepsis accounts for 40–60% of hospital-acquired AKI cases. **Mnemonic for ATN causes:** **SHIN** = **S**epsis/Shock, **H**emolysis/Myoglobinuria, **I**schemia, **N**ephrotoxins (aminoglycosides, contrast, NSAIDs). ### Histological Features - Loss of brush border on proximal tubular cells - Flattening of epithelium - Cellular debris and casts in tubular lumen - Intact basement membrane (distinguishes from necrosis) - Regeneration possible if cause is removed