Idiopathic acute pancreatitis - A myth or reality? Role of endoscopic ultrasonography and magnetic resonance cholangiopancreatography in its diagnosis

Background Around 10% to 30% patients with acute pancreatitis (AP) do not have a cause after the routine investigations, and are considered as having idiopathic acute pancreatitis (IAP). Establishing the etiology in such patients will prevent recurrences and evolution to chronic pancreatitis. Endoscopic ultrasonography (EUS) and magnetic resonance cholangiopancreatography (MRCP) characteristically are used to diagnose IAP when routine methods fail, but their exact role is not determined. Methods This prospective study was undertaken in a tertiary care hospital, in which patients admitted initially with diagnosis of IAP were evaluated. These patients underwent MRCP and EUS at least 4 weeks after an attack of AP. The results of EUS and MRCP were compared and analyzed with various clinical variables using suitable statistical tests. Results A total of 31 patients with IAP were included. EUS and/or MRCP was able to establish at least one etiology in 17 patients (54.8%). The diagnoses revealed were gallbladder (GB) microlithiasis, GB sludge, choledocholithiasis, pancreatobiliary ductal anomalies, pancreatic adenocarcinoma, and intraductal papillary mucinous neoplasm. Comparing the diagnostic accuracy of both the modalities, EUS (14/31) was able to diagnose more cases than MRCP (8/31). The diagnostic capability of EUS was lower in patients who had a cholecystectomy (12.5% vs. 56.5%; p = 0.03). Conclusions EUS and MRCP are useful modalities in the etiological diagnosis of IAP and should be used in conjunction. EUS is better for establishing a possible biliary etiology and MRCP for an anatomical alteration in pancreatobiliary ducts.