INTRODUCTION
A wide spectrum of anomalies in the pancreas,
the pancreatic ductal system,
and biliary tree are not infrequently and are commonly encountered at radiologic examinations.
May create a diagnostic challenge and not be detected until adulthood,
often discovered as an incidental finding in asymptomatic patients.
The knowledge and recognition of the normal anatomy will help in understanding and identifying these variants,
so important in clinical management for avoiding misdiagnosis,
helping in surgical planning to prevent inadvertent ductal injury.
ANATOMY
BILIARY SYSTEM
The intrahepatic biliary system runs parallel to the portal venous vessel.
The right hepatic duct (RHD) drains the right hepatic lobe and has two major branches: the right posterior duct (RPD) with a horizontal course,
and the right anterior duct (RAD) who tends to have a more vertical orientation.
The RPD fuses with the RAD to form the RHD.
The left hepatic duct (LHD) drains the left hepatic lobe.
The bile duct draining the caudate lobe usually joins the origin of the RHD or LHD.
The typically short RHD and the longer LHD fuses to form the common hepatic duct (CHD).
The cystic duct (CD) classically joins the CHD above the pancreas and about 2cm below the confluence of the right and left hepatic ducts with a lateral approach,
although there are variants of drainage more proximal or distal,
parallel,
or spiral around the CHD.
PANCREAS
The pancreas is a lobulated gland of 15–20 cm,
located in the retroperitoneum.
Can be divided into four segments: head,
neck,
body,
and tail.
The pancreatic head is located within the duodenum,
to the right of the superior mesenteric vein.
The uncinate process has a triangular appearance and is a caudal prolongation of the head.
The pancreatic neck is to the left of the head and ventral to the superior mesenteric vein.
The pancreatic body and tail are located behind the stomach,
and the border between these two portions is not clearly defined.
The diameter of the main pancreatic duct (MPD) is between 1.5-3.5 mm and has approximately 20–30 side branches that enter the duct.
There are multiple ductal configurations.
The usually long duct of Wirsung (WD) or ventral duct,
unites with the common bile duct (CBD),
traverse the sphincter of Oddi to enter the duodenum and drains into the major papilla.
In most cases these two ducts unite within this sphincteric segment.
This common channel may be long or short.
The usually short duct of Santorini (SD),
or accessory duct or dorsal duct, goes to the minor papilla and drains the anterior and superior portion of the head.