Etiology and Pathogenesis of Acute Pancreatitis

Acute pancreatitis is a disorder that has numerous causes and an obscure pathogenesis. Bile duct stones and alcohol abuse together account for about 80% of acute pancreatitis. Most episodes of biliary pancreatitis are associated with transient impaction of the stone in the ampulla (that causes obstruction of the pancreatic duct, with ductal hypertension) or passage of the stone though and into the duodenum. Other causes of acute pancreatitis are various toxins, drugs, other obstructive causes (such as malignancy or fibrotic sphincter of Oddi), metabolic abnormalities, trauma, ischemia, infection, autoimmune diseases, etc. In 10% of cases of acute pancreatitis, no underlying cause can be identified; this is idiopathic pancreatitis. Occult biliary microlithiasis may be the cause of two thirds of the cases of "idiopathic" acute pancreatitis. Intra-acinar activation of trypsinogen plays a central role in the pathogenesis of acute pancreatitis, resulting in subsequent activation of other proteases causing the subsequent cell damage. Ischemia/reperfusion injury is increasingly recognized as a common and important mechanism in the pathogenesis of acute pancreatitis and especially in the progression from mild edematous to severe necrotizing form. Increased intracellular calcium concentration also mediates acinar cell damage. Oxygen-derived free radicals and many cytokines (e.g., interleukin [IL]-1, IL-6, IL-8, tumor necrosis factor-alpha, platelet activating factor) are considered to be principal mediators in the transformation of acute pancreatitis from a local inflammatory process into a multiorgan illness.