Background: In patients with recurrent pancreatitis of unknown etiology and nondilated ducts, accurate morphofunctional evaluation of the pancreaticobiliary ductal system and sphincter of Oddi function is important in the diagnostic workup. However, ERCP and sphincter of Oddi manometry may be nondiagnostic and postprocedure complications may be frequent.
Objective: Our purpose was to assess the diagnostic accuracy of the magnetic resonance cholangiopancreatography with secretin test (MRCP-S) in patients with recurrent acute pancreatitis of unknown etiology. Accuracy was established on the basis of ERCP findings and a minimum of 24 months' clinical follow-up.
Design: Thirty-seven consecutive patients with intact gallbladder and a nondilated pancreaticobiliary ductal system with nonpathologic EUS findings entered a prospective MRCP-S-guided and ERCP-guided diagnostic and therapeutic study protocol.
Results: Patients were followed up for a mean of 31.3 months (range 26-38 months). MRCP-S identified some pancreatic outflow impairment, suggesting morphofunctional dysfunction of either the major or minor papilla, in 12 of 37 patients (32.4%). The addition of ERCP to MRCP-S did not substantially improve the diagnostic yield for the etiology of recurrent pancreatitis, and 13.6% of cases had mild postprocedure pancreatitis. The S-test was abnormal in 12 of 20 cases (60%) in whom some dysfunction of the sphincter of Oddi or minor papilla was assumed on the basis of follow-up findings. The outcome was successful after biliary or pancreatic sphincterotomy in all patients with an abnormal S-test result. Sensitivity, specificity, and positive and negative predictive values of the S-test for the diagnosis of pancreatic outflow impairment at the major or minor papilla were, respectively, 57.1%, 100%, 100%, and 64%. When the test showed an abnormal result, we were unable to distinguish between biliary and pancreatic segment dysfunction of the sphincter of Oddi.
Conclusions: In idiopathic recurrent pancreatitis with nondilated ducts, the MRCP-S-guided approach gave diagnostic accuracy comparable to ERCP with regard to morphologic lesions, and it can be used as an alternative, avoiding ERCP-related complications in the diagnostic phase. An abnormal S-test result showed an excellent positive predictive value and somewhat disappointing negative predictive value for sphincter of Oddi or minor papilla dysfunction and for clinical success of therapeutic endoscopic approach.