Acute pancreatitis involves autodigestion of the pancreas by its own secretions. The anatomical signal is tryptic necrosis. The so‐called edematous pancreatitis cannot be compared with acute tryptic pancreatitis as it is caused by swelling of the pancreas, with pancreatic juice in the parenchyma, but no necrosis occurs. The severity of acute pancreatitis is determined by the state of preservation of the pancreatic capsule. Three stages may exist: (a) the gland is enlarged with solitary areas of necrosis and the capsule is preserved; (b) confluent necrosis with necrosis of the lipid tissue occurs, but the capsule is preserved; and (c) necrosis extends into surrounding areas, especially into the omental bursa and the retroperitoneum, and the capsule is destroyed. Peritonitis, ileus, and pleural effusion may represent regional extension of acute pancreatitis. Shock is the most dangerous complication and is the most frequent cause of death.