What is the normal CT and MRI appearance of the pancreas?
The pancreas is approximately 15 cm in length and 2 to 3 cm in width and is located within the anterior pararenal space of the retroperitoneum. It can be subdivided into the pancreatic uncinate process, head, neck, body, and tail. The pancreatic head is located to the left of the second portion of the duodenum, and the pancreatic body and tail are located posteriorly to the gastric body and antrum. In general, the pancreatic body and tail are slightly more superiorly located than the pancreatic head and uncinate process. Pancreatic size tends to decrease with increasing age. In younger people, the pancreas typically has a smooth contour and homogeneous attenuation, signal intensity, and enhancement, whereas in older people, the pancreas typically becomes more lobulated and more inhomogeneous due to fatty change (which may be diffuse or focal). On MRI, the pancreas typically has the highest T1-weighted signal intensity among all abdominal organs (excluding abdominal fat).
The main pancreatic duct is normally ≤ 2 to 3 mm in caliber but may measure up to 5 mm in caliber in elderly patients. The main pancreatic duct (of Wirsung) typically joins the common bile duct to form the ampulla of Vater and then drains into the second portion of the duodenum through the major duodenal papilla (of Vater). An accessory pancreatic duct (of Santorini) may occasionally be present more superiorly, which drains more superiorly and anteriorly into the second portion of the duodenum through the minor duodenal papilla. The common bile duct is typically located in the right posterolateral aspect of the pancreatic head. Approximately 20 to 35 short pancreatic ductal side branches join perpendicularly to the main pancreatic duct.