The pancreatic duct, or duct of Wirsung (also, the Major pancreatic duct due to the existence of an accessory pancreatic duct), is a duct joining the pancreas to the common bile duct to supply pancreatic juices which aid in digestion provided by the "exocrine pancreas". The pancreatic duct joins the common bile duct just prior to the ampulla of Vater, after which both ducts perforate the medial side of the second portion of the duodenum at the major duodenal papilla. Most people have just one pancreatic duct. However, some have an additional accessory pancreatic duct, called the Duct of Santorini. Compression, obstruction or inflammation of the pancreatic duct may lead to acute pancreatitis. The most common cause for obstruction is choledocholithiasis, or gallstones in the common bile duct. Obstruction can also be due to Duodenal Inflammation in Crohn's Disease. A gallstone may get lodged in the constricted distal end of the ampulla of Vater, where it blocks the flow of both bile and pancreatic juice into the duodenum. Bile backing up into the pancreatic duct may initiate pancreatitis. Pancreatic ductal carcinoma is a common form of pancreatic cancer.