From the Guidelines
The presence of an accessory duct is not a specific indication for Magnetic Resonance Cholangiopancreatography (MRCP) [ 1 ]. However, MRCP may be considered in patients with suspected pancreaticobiliary malformations, including those with an accessory duct, to evaluate the anatomy and potential complications such as choledochal cysts or pancreatitis.
Key Points to Consider
- In patients undergoing MRCP for evaluation of an accessory duct, a standard dose of 1-2 mL of secretin may be administered to enhance visualization of the pancreatic ductal system, with imaging performed 5-10 minutes after injection.
- MRCP is more sensitive than US for determining the cause of biliary obstruction when dilated bile ducts are seen on US [ 1 ].
- MRCP is the preferred imaging modality in patients with suspected sclerosing cholangitis or biliary stricture, avoiding the possibility of suppurative cholangitis that may be induced by endoscopic catheter manipulation of an obstructed biliary system [ 1 ].
- The use of MRCP may decrease the number of ERCP examinations obtained prior to elective cholecystectomy [ 1 ].
Clinical Considerations
- MRCP is less morbid than ERCP imaging; however, ERCP imaging offers the potential for intervention (CBD stone extraction or biopsy of an obstructing lesion) [ 1 ].
- MRI performed with diffusion sequences and gadoxetate disodium is more sensitive than CT for the detection of liver metastases from pancreaticobiliary malignancies [ 1 ].
From the Research
Accessory Duct and MRCP
- The study 2 found that MRCP can accurately demonstrate the normal pancreatic duct as well as various pancreatic duct abnormalities, including congenital anomalies of the biliary tree and pancreatic duct.
- In this study, the accessory pancreatic duct and secondary branches in the head, body, and tail of the pancreas were depicted in 11 (26%), eight (19%), four (10%), and two (5%) of the control patients, respectively.
- Another study 3 investigated the frequency of pancreatic ductal variants using MRCP and found a new subtype of the type C variant, which could be called "pancreas divisum inversus", where the accessory pancreatic duct (APD) was long and originated in the lower portion of the pancreatic head.
MRCP Capabilities
- MRCP is a noninvasive diagnostic modality capable of producing high-quality images of the biliary tree and pancreatic duct 2.
- It can detect pancreatic duct injuries and pseudocysts, and provide information that may be used to guide management decisions 4.
- MRCP is useful in the evaluation of pancreatic and biliary disorders, and can image the entire pancreaticobiliary tract during a single breath hold 5.
Diagnostic Accuracy
- The study 6 compared the usefulness of cystic duct three-dimensional computed tomography with non-contrast for before laparoscopic cholecystectomy and endoscopic transpapillary gallbladder drainage in comparison to MRCP, and found that cystic duct 3D-CT using non-contrast CT is a useful technique for understanding anatomical variations of the cystic duct and accessory bile duct.
- The comparison results with MRCP showed sensitivity=83.3%, specificity=78.0%, positive predictive value=47.6%, and negative predictive value=95.1% 6.