Accessory Pancreatic Duct: Anatomy, Course, Variations, Function, Clinical Significance, MRI & CT Imaging

Topic

Accessory pancreatic duct

The accessory pancreatic duct, also known as the duct of Santorini, is a secondary pancreatic duct that usually drains the anterior portion of the head of the pancreas. It is the embryologic remnant of the dorsal pancreatic duct system. In many individuals, it persists and provides an additional drainage pathway into the duodenum through the minor duodenal papilla, located proximal and superior to the major papilla.

Although often small or functionally insignificant, it is clinically important because its patency and variations can influence pancreatic drainage and predispose to certain pancreaticobiliary disorders.

Synonyms

Duct of Santorini
Minor pancreatic duct
Accessory duct of the pancreas

Origin, Course, and Termination

Origin: Branches from the main pancreatic duct (duct of Wirsung), typically in the head of the pancreas
Course: Runs superior and anterior within the pancreatic head toward the minor papilla
Termination: Opens into the minor duodenal papilla, about 2 cm proximal to the major papilla in the second part of the duodenum

Relations

Anteriorly: Duodenal wall (second part)
Posteriorly: Head of the pancreas and main pancreatic duct
Superiorly: Common bile duct
Inferiorly: Main pancreatic duct (duct of Wirsung) and major papilla

Function

Provides an accessory drainage pathway for pancreatic juice into the duodenum
In some cases, remains the primary drainage route if the main pancreatic duct is atretic or stenosed
Acts as a safety mechanism to reduce intrapancreatic ductal pressure

Clinical Significance

Pancreas divisum: Failure of fusion of dorsal and ventral pancreatic ducts; the accessory duct may become the dominant drainage pathway, potentially predisposing to recurrent pancreatitis
Minor papilla obstruction: May lead to impaired drainage and pancreatitis
Anatomical variants: Varying size and patency can complicate surgical or endoscopic interventions
Endoscopic retrograde cholangiopancreatography (ERCP): Identification is critical during pancreatic duct cannulation

MRI Appearance

T1-weighted images:

Not typically visualized unless dilated; appears as low signal tubular structure if seen
Surrounding pancreatic parenchyma shows intermediate signal

T2-weighted images:

Duct fluid appears bright
Accessory duct seen as a fine high-signal tubular structure in pancreatic head

STIR (Short Tau Inversion Recovery):

Duct fluid remains bright
Surrounding fat suppressed, improving duct conspicuity

T1 Fat-Sat Post-Contrast:

Normal duct does not enhance
Surrounding inflammatory or neoplastic changes may enhance

T2 Fat-Saturated HASTE (single-shot):

Accessory duct: bright, thin linear structure in pancreatic head
Stones, strictures, or air bubbles appear as dark filling defects
Excellent for rapid evaluation of duct patency

T2 TSE Fat-Saturated 3D (MRCP sequence):

Duct visualized as a continuous bright tubular structure joining or parallel to the main pancreatic duct
Allows 3D reconstruction of ductal anatomy and variants
Excellent for diagnosis of pancreas divisum

Thick-slab T2 Fat-Saturated HASTE:

Shows the accessory duct as part of the biliary–pancreatic system in a projectional image
Highlights communication with main pancreatic duct and opening into the minor papilla
Filling defects (stones, strictures) seen as dark spots within bright fluid

CT Appearance

Non-Contrast CT:

Normally not visible unless dilated
Appears as a fine low-attenuation tubular structure in pancreatic head when dilated
Calcified stones may be detected if present

Post-Contrast CT: