Accessory pancreatic duct

At a glance

English

Accessory pancreatic duct

Latin (TA2)

Ductus pancreaticus accessorius

System

Digestive

Region

Abdomen

Side

Single, on the midline

About the accessory pancreatic duct

Known by the eponym duct of Santorini, the accessory pancreatic duct is a narrow channel in the head of the pancreas. Not everyone has a working one. Where it is present, it collects pancreatic juice from the upper and front part of the head and carries it towards the descending (second) part of the duodenum, alongside the much larger main pancreatic duct.

Its course is short and nearly horizontal. It usually leaves the main duct inside the head of the gland and runs forwards and upwards, above the main duct, to end on the minor duodenal papilla. That small mound lies on the inner wall of the descending duodenum, roughly two centimetres above and slightly in front of the major papilla, where the main duct and the bile duct open together. In some people the accessory duct does not reach the bowel at all and instead empties back into the main duct, so that all pancreatic juice leaves through the major papilla.

The two ducts are a legacy of how the gland forms. The pancreas begins as two buds of the embryonic gut, a dorsal and a ventral one. The ventral bud swings round behind the duodenum and fuses with the dorsal bud, and their duct systems join. The main duct is made from the ventral duct together with the far part of the dorsal duct; the near part of the dorsal duct, if it persists, becomes the accessory duct.

Clinically the duct matters mostly when that fusion fails. In pancreas divisum the two systems stay separate and most of the gland drains through the accessory duct and the small minor papilla. The narrow outlet can be outpaced by the flow, which is linked in some people to repeated attacks of pancreatitis. Endoscopists looking for the minor papilla during a procedure on the ducts must keep this variant in mind.

Function and supply

Begins at

Branches inside the upper and anterior part of the head of the pancreas, usually leaving the main pancreatic duct within the gland.

Ends at

Opens on the minor duodenal papilla, high on the descending duodenum, or in some people drains back into the main pancreatic duct instead.

Function

Carries pancreatic juice, rich in digestive enzymes and bicarbonate, from part of the pancreatic head into the duodenum.

Blood supply

Its wall is supplied by small branches of the superior and inferior pancreaticoduodenal arteries that run around the head of the pancreas.