The exocrine pancreas drains into the gastrointestinal tract via the main and accessory pancreatic ducts. Several anatomical variations of the typical ductal drainage pattern exist, reflecting variations in the embryological development and fusion of the dorsal and ventral pancreatic buds 13,14. These variants may have clinical or physiological implications, e.g. risk of pancreatitis, or surgical reconstruction.
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Gross anatomy
The exocrine pancreatic tissue drains into multiple small lobular ducts, which drain into the larger main duct (and larger accessory ducts) and finally into the second part of the duodenum. The main pancreatic duct usually joins the common bile duct in the head of the pancreas, as outlined below 13,14.
With typical conventional anatomy, most of the pancreas is drained by the main pancreatic duct, with the uncinate process and lower head drained by an accessory duct 12,13. The main and accessory ducts frequently communicate with each other, although there are several ductal variations, as outlined below.
Nomenclature of the main pancreatic duct can be confusing 10-12:
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based on distance from pancreatic head: proximal (head region); distal (tail region)
this aligns with surgical terminology: a distal pancreatectomy involves the removal of the pancreatic body and tail
based on the direction of secretion flow: proximal (tail region); distal (head region)
radiologically, it may be best to refer to duct location by region, e.g. "duct in the head region" to avoid confusion
Main pancreatic duct (of Wirsung)
The main pancreatic duct (also known as the duct of Wirsung 13,14) runs through the center of the gland from left to right (i.e. toward the duodenum). It drains most of the pancreas (the embryological dorsal bud), except for the uncinate process and inferior aspect of the head. The pancreatic duct typically joins the common bile duct at a 60-degree angle at the hepatopancreatic ampulla, before draining into the ampulla of Vater through the Sphincter of Oddi.
The pancreatic duct typically measures up to 3 mm at the head, 2 mm in the body, and 1 mm in the tail 14.
Accessory pancreatic duct (of Santorini)
The accessory pancreatic duct (also known as the duct of Santorini or Bernard) drains the uncinate process and lower part of the head (of the migrated ventral pancreatic bud). The accessory duct typically communicates with the main duct 13,14.
Variant anatomy
Variants of the pancreas which result in ductal variations are covered in the pancreas article.
Pancreas divisum
A pancreas divisum is the most common variation of pancreatic duct formation and can account for up to 14% 3. It results from the failure of fusion of dorsal and ventral pancreatic anlages. As a result, the dorsal pancreatic duct drains most of the pancreatic glandular parenchyma via the minor papilla. Although controversial, this variant is considered a cause of pancreatitis 1,3.
Pancreatic divisum can result in a santorinicele 2, which is a cystic dilatation of the distal dorsal duct, immediately proximal to the minor papilla.
Three subtypes are known 5:
type 1 (classic): no connection at all; occurs in the majority of cases (~70%)
type 2 (absent ventral duct): minor papilla drain all of pancreas while major papilla drains bile duct (~25%)
type 3 (functional): filamentous or inadequate connection between dorsal and ventral ducts (~5%)
Meandering main pancreatic duct
Meandering main pancreatic duct (MMPD) comprises a reverse Z-type and loop-type of pancreatic ducts.
Ansa pancreatica
Ansa pancreatica is a rare anatomic variation of the pancreatic ducts. It is a communication between the main pancreatic duct and the accessory pancreatic duct.
Anomalous pancreaticobiliary junction
Anomalous pancreaticobiliary junction refers to the union of the pancreatic duct and common bile duct outside the duodenal wall.
History and etymology
The duct of Wirsung was first reported in an etching by Johann Georg Wirsung (1589-1643), a German-Italian anatomist 8.
The accessory pancreatic duct of Santorini is named after Giovanni Domenico Santorini (1681-1737), an Italian professor of medicine 8.
