Natural course of acute pancreatitis.

Acute pancreatitis comprises, in terms of clinical, pathologic, biochemical, and bacteriologic data, four entities. Interstitial edematous pancreatitis and necrotizing pancreatitis are the most frequent clinical manifestations; pancreatic pseudocyst and pancreatic abscess are late complications after necrotizing pancreatitis, developing after 3 to 5 weeks. Determinants of the natural course of acute pancreatitis are pancreatic parenchymal necrosis, extrapancreatic retroperitoneal fatty tissue necrosis, biologically active compounds in pancreatic ascites, and infection of necrosis. Early in the course of acute pancreatitis multiple organ failure is the consequence of various inflammatory mediators that are released from the inflammatory process and from activated leukocytes attracted by pancreatic injury. During the late course, starting the second week, local and systemic septic complications are dominant. Around 80% of deaths in acute pancreatitis are caused by septic complications. The infection of pancreatic necrosis occurs in 8% to 12% of acute pancreatitis and in 30% to 40% of patients with necrotizing pancreatitis. Bacteriologic analysis of intraoperative smears and aspirates reveals predominantly gram-negative germs deriving from the intestine, most frequently Escherichia coli. It has been confirmed that after necrotizing pancreatitis a considerable large group of patients suffer long-lasting exocrine and endocrine insufficiency.