Secretin-Enhanced MRCP: Review of Technique and Application ...

Sanyal et al.Fig. 11—42-year-old woman who underwentpostsurgical evaluation with secretin-enhancedMRCP. Patient had reimplantation of dorsal andventral ducts after pancreas-sparing duodenectomyfor familial adenomatous polyposis. SecretinenhancedMRCP showed overall reduced pancreaticfunction, with reimplanted dorsal duct contributingall pancreatic secretions.the volume of fluid secreted into the duodenumserves as a proxy for bicarbonate levels;thus, reduction in the volume of fluid correlateswith exocrine dysfunction. In patientswith normal exocrine function, fluid appearsrapidly in the periampullary duodenum aftersecretin administration, then fills and distendsthe duodenal bulb and progresses pastthe genu. In patients with chronic pancreatitis,the appearance of fluid in the duodenumis often delayed and duodenal filling and distentionare reduced.Role of Secretin-Enhanced MRCP in Evaluationof Recurrent PancreatitisSecretin-enhanced MRCP helps in the evaluationof patients with recurrent episodes ofpancreatitis. Pancreatic ductal strictures cancause recurrent attacks of pancreatitis. Distentionof the MPD in secretin-enhanced MRCPhelps delineate MPD strictures better, whichcan guide further treatment [13, 18] (Fig. 7).Collapsed segments of the duct that may bemistaken for strictures on presecretin imagesdistend after secretin administration. SecretinenhancedMRCP has an advantage over ERCPbecause of the inability of ERCP to delineatethe duct proximal to very severe stenosis.Pancreas divisum has been associatedwith recurrent pancreatitis because of thepresumed inadequate pancreatic drainagethrough the accessory duct. The distentionof the ductal system in secretin-enhancedMRCP improves the diagnosis of pancreasdivisum [14, 20, 21] (Fig. 8). Focal cystic dilationof the accessory duct or Santorinicelehas been considered as a possible cause ofrelative stenosis of the accessory duct. Secretin-enhancedMRCP also improves the diagnosisof Santorinicele [13] (Fig. 9).Secretin-enhanced MRCP has also beenused to show pancreatic ductal disconnectionresulting from pancreatic necrosis or trauma[22]. This condition leads to disconnectionof viable pancreatic tissue from the gastrointestinaltract and recurrent episodes of inflammationor fistula formation (Fig. 10).However, the frequent presence of adjacentfluid collections and suboptimal response ofthe inflamed pancreas make detecting smallleaks challenging [8]. Secretin-enhancedMRCP can also be used to evaluate the pancreaticductal system in postsurgical patients.Cannulation of the pancreatic duct by ERCPis often difficult in such patients because ofthe altered postsurgical anatomy (Fig. 11).Fig. 12—51-year-old man with side branch intraductal papillary mucinous neoplasm (IPMN).A, Presecretin image shows lobulated cyst adjacent to main pancreatic duct in pancreatic body. Nocommunication is noted.B, Image obtained at 4 minutes after secretin injection shows communication (arrowhead), confirmingdiagnosis of side branch IPMN.ABPancreatic Cystic Neoplasms and Secretin-Enhanced MRCPThere has been a recent surge in interestin cystic pancreatic lesions, particularly intraductalpancreatic mucinous neoplasms.Secretin-enhanced MRCP is being increasinglyused to evaluate these neoplasms [23].The basis of performing secretin-enhancedMRCP for cystic pancreatic lesions is thatthe ductal distention after secretin injectionABFig. 13—46-year-old man with multiple side branchintraductal papillary mucinous neoplasms (IPMNs).A, Image obtained 1 minute after secretin injectionshows multiple small pancreatic cysts.B, Image obtained 10 minutes after secretin injectionshows cysts become brighter, suggesting ductalcommunication and confirming diagnosis of sidebranch IPMNs.128 AJR:198, January 2012