## Why Saponification of fat by pancreatic lipase is right The chalky white fat necrosis spots (marked **B**) in acute pancreatitis result from saponification—the conversion of neutral fats to fatty acids and glycerol by pancreatic lipase that is released during pancreatic inflammation and necrosis. These liberated fatty acids combine with calcium to form insoluble calcium soaps, which appear as chalky white deposits on gross examination. This is a hallmark histopathologic finding of acute pancreatitis and reflects the severity of pancreatic injury. (Harrison 21e Ch 374) ## Why each distractor is wrong - **Calcification of pancreatic ductal epithelium**: This describes changes seen in chronic pancreatitis (pancreatic calcifications, ductal dilatation), not the acute fat necrosis of acute pancreatitis. The timeline and mechanism are entirely different. - **Hemorrhagic necrosis with iron deposition**: While hemorrhage may occur in severe necrotizing pancreatitis (marked **D**), iron deposition produces brown or rust-colored lesions, not chalky white spots. This confuses the hemorrhagic component with the fat necrosis component. - **Bacterial colonization and abscess formation**: Infected necrosis and abscess formation are late complications (≥1 week, late phase per Revised Atlanta Classification) and produce purulent material, not chalky white fat necrosis. This is a secondary complication, not the primary mechanism of the white spots. **High-Yield:** Fat necrosis in acute pancreatitis = saponification (lipase + fat → fatty acids + glycerol + calcium → calcium soaps = chalky white spots). This is acute; chronic pancreatitis shows pancreatic calcifications instead. [cite: Harrison 21e Ch 374]
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