Can MRCP replace ERCP for the diagnosis of autoimmune pancreatitis?

ABSTRACT

BACKGROUND: It is of utmost importance that autoimmune pancreatitis (AIP) be differentiated from pancreatic cancer. Irregular narrowing of the main pancreatic duct is a characteristic finding in AIP; it is useful for differentiating AIP from pancreatic cancer stenosis. This study evaluated the usefulness of magnetic resonance cholangiopancreatography (MRCP) for the diagnosis of AIP and assessed whether MRCP could replace endoscopic retrograde cholangiopancreatography (ERCP) for diagnosing AIP. METHODS: The MRCP and ERCP findings of 20 AIP patients were compared. RESULTS: On MRCP, the narrowed portion of the main pancreatic duct was not visualized, while the noninvolved segments of the pancreatic duct were visualized. The degree of upstream dilatation of the proximal main pancreatic duct was milder in AIP than in pancreatic cancer patients. In the skipped type, only skipped narrowed lesions were not visualized. After steroid therapy for AIP, the nonvisualized main pancreatic duct became visualized. CONCLUSIONS: MRCP cannot replace ERCP for the diagnosis of AIP, since narrowing of the main pancreatic duct in AIP was not visualized on MRCP. MRCP findings of segmental or skipped nonvisualized main pancreatic duct accompanied by a less dilated upstream main pancreatic duct may suggest the presence of AIP. MRCP is useful for following AIP patients.