## Most Common Cause of Acute Cholecystitis **Key Point:** Gallstone impaction in the cystic duct accounts for 80–90% of acute cholecystitis cases, making it the overwhelmingly most common etiology. ### Pathophysiology 1. Stone lodges in cystic duct → obstruction of bile outflow 2. Bile stasis → increased intraluminal pressure 3. Mucosal ischemia and chemical inflammation 4. Secondary bacterial infection (E. coli, Klebsiella) in ~50% of cases 5. Acute cholecystitis develops over hours to days ### Clinical Presentation - Acute RUQ pain (often colicky initially, then constant) - Murphy's sign positive (inspiratory arrest during palpation) - Fever and leukocytosis indicate inflammation ± infection - Ultrasound: gallstones + pericholecystic fluid + wall thickening **High-Yield:** The term "acute cholecystitis" is synonymous with cystic duct obstruction by stone in the vast majority of cases. This is the most tested scenario in NEET PG. ### Acalculous Cholecystitis (10–15% of cases) - Occurs without gallstones - Risk factors: critical illness, sepsis, prolonged NPO, TPN, trauma - Worse prognosis than calculous disease - Often requires urgent percutaneous cholecystostomy **Clinical Pearl:** In a patient with acute cholecystitis and imaging confirmation of stones, the diagnosis is secure and management is standardized (antibiotics, NPO, fluids, then cholecystectomy).
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