Secretin-Enhanced MRCP: How and Why- AJR Expert Panel Narrative Review

Abstract

Secretin-enhanced MRCP (S-MRCP) has advantages over standard MRCP for imaging of the pancreaticobiliary tree. Through the use of secretin to induce fluid production from the pancreas and leveraging of fluid-sensitive MRCP sequences, S-MRCP facilitates visualization of ductal anatomy, and the findings provide insight into pancreatic function, allowing radiologists to provide additional insight into a range of pancreatic conditions. This narrative review provides detailed information on the practical implementation of S-MRCP, including patient preparation, logistics of secretin administration, and dynamic secretin-enhanced MRCP acquisition. Also discussed are radiologists' interpretation and reporting of S-MRCP examinations, including assessments of dynamic compliance of the main pancreatic duct and of duodenal fluid volume. Established indications for S-MRCP include pancreas divisum, anomalous pancreaticobiliary junction, Santorinicele, Wirsungocele, chronic pancreatitis, main pancreatic duct stenosis, and assessment of complex postoperative anatomy. Equivocal or controversial indications are also described along with an approach to such indications. These indications include acute and recurrent acute pancreatitis, pancreatic exocrine function, sphincter of Oddi dysfunction, and pancreatic neoplasms.

Keywords: MRCP; MRI; pancreas; secretin.

Figure 1.

Example of setting planes for radial slab 2D MRCP sequences in a 44-year-old woman with chronic abdominal pain. Slabs can be chosen on an axial fast acquisition T2-weighted sequence. These should be centered on the distal common bile duct, each angled 5–10 degrees from one another.

Figure 2.

Expected dynamic compliance of the main pancreatic duct in 50-year-old woman with upper abdominal pain. (A) Coronal MRCP shows normal configuration of the main pancreatic duct with no visible dilated side branches. (B) Coronal secretin-enhanced MRCP obtained 5 minutes after secretin administration, showing expected dynamic dilation of the main pancreatic duct. Pancreatic fluid has started to fill the duodenal lumen (long arrow). Incidental note is made of a duodenal diverticulum (short arrow).

Figure 3.

Expected filling of the duodenum with fluid after secretin administration, demonstrated in 48-year-old man with right upper quadrant pain. (A) MRCP before secretin administration shows the duodenum with minimal physiologic fluid. There is progressively increased fluid signal throughout the duodenum at 2 minutes (B) and 6 minutes (C). At 9 minutes (D), fluid is beyond the duodenal genu (arrow), consistent with grade 3 response to secretin.

Figure 4.

Pancreas divisum and Santorinicele, demonstrated in 76-year-old woman with chronic abdominal pain. (A) Coronal MRCP shows complete pancreas divisum. Common bile duct drains into the duodenum at the major papilla, while the dorsal pancreatic duct (duct of Santorini) drains entirely through the minor papilla (arrow). Ventral pancreatic duct is not visible. (B) Coronal secretin-enhanced MRCP shows saccular dilatation of the terminal portion of the dorsal duct, termed Santorinicele (long arrow). The ventral pancreatic duct becomes faintly visible (short arrow). Both findings were not visible before secretin administration.

Figure 5.

Anomalous pancreaticobiliary junction on secretin-enhanced MRCP, demonstrated in 22-year-old woman who is status post choledochal cyst resection and Roux-en-Y hepaticojejunostomy. Patient also has a long common channel secondary to anomalous junction of the common bile duct with the pancreatic duct (arrow).

Figure 6.

Duct penetrating sign in 58-year-old woman with history of alcohol-related pancreatitis and a dilated main pancreatic duct on prior CT. (A) Radial slab MRCP demonstrate an abrupt-appearing stricture of the main pancreatic duct (arrow). (B) Secretin-enhanced MRCP shows a narrow, but present, duct downstream to the stricture, consistent with the duct-penetrating sign. This proved to be a benign stricture related to chronic pancreatitis.

Figure 7.

Main pancreatic duct leak 53-year-old man with multiple bouts of acute pancreatitis. A stricture of the main pancreatic duct (short arrows) is seen on MRCP before secretin administration (A). At 1 minute after secretin administration (B), fluid accumulates in the stomach, consistent with a pancreaticogastric fistula. Fluid progresses into the duodenum at 2 minutes (C) and 5 minutes (D). The downstream main pancreatic duct does not dilate (curved arrow) given flow of pancreatic fluid through the fistula.

Figure 8.

Postoperative pancreatic duct leak in 30-year-old man with history of distal pancreatectomy, splenectomy, and gastrojejunostomy. (A) Coronal MRCP before secretin administration shows remaining pancreatic duct (arrow). (B) Coronal secretin-enhanced MRCP shows a new fluid collection upstream to the remaining pancreatic duct, indicating a postoperative leak (arrow).

Figure 9.

Imaging in sphincter of Oddi dysfunction in 45-year-old woman with biliary-type pain and abnormal findings on endoscopic sphincter manometry. (A) Coronal MRCP obtained before secretin administration shows nonspecific dilation of the common bile duct with smooth distal tapering. The main pancreatic duct measures up to 2 mm and does not show prominent side branches. (B) Coronal secretin-enhanced MRCP obtained 2 minutes after secretin administration shows an increase in main pancreatic duct diameter up to 5.5 mm. Multiple duct side branches show increased prominence (arrows).

Figure 10.

Imaging in sphincter of Oddi dysfunction (SOD) in 55-year-old man with right upper quadrant pain and clinical diagnosis of type II SOD. (A) Coronal MRCP obtained before secretin administration shows the main pancreatic duct without irregularity, dilation, or abnormal side branches. (B) Coronal MRCP obtained 3 minutes after secretin administration shows diffuse fluid signal surrounding the main pancreatic duct (arrows). This represents acinarization, or diffusely increased T2 signal surrounding the main pancreatic duct. Increased pressure in the main pancreatic duct is thought to lead to overfilling of pancreatic duct side-branches with fluid.