Background and study aims: Unexplained pancreatitis represents a diagnostic challenge. The aim of this study was to determine the diagnostic utility of endoscopic retrograde cholangiopancreatography (ERCP) with sphincter of Oddi manometry (SOM), bile analysis, and endoscopic ultrasound (EUS) in evaluating such patients. Patients and methods: Of 162 patients referred for evaluation of pancreatitis, 72 with a known cause were excluded. The remainder (n = 90) was classified as having prior acute (n = 24) or recurrent acute pancreatitis (n = 66). Bile sampling and SOM were performed at the time of ERCP. EUS was used to assess for tumors and for chronic pancreatitis. Clinical outcomes were evaluated by questionnaire. Results: ERCP was successful in 88/89 patients (99%). Manometry was successful in 63/67 patients (94%), and 56 patients underwent EUS. Findings were categorized into five distinct etiologies: sphincter of Oddi dysfunction (SOD) (n = 28; 31%), pancreas divisum (n = 18; 20%), biliary (n = 18; 20%), idiopathic (n = 18; 20%) and tumor-related (n = 8; 9%). Features of moderate or severe chronic pancreatitis by EUS and ERCP criteria were found in 18 patients (21%); an additional nine patients had chronic pancreatitis by EUS criteria alone. EUS identified all the tumors. The condition was improved in 96% of all patients undergoing endoscopic therapy. Conclusion: An etiology was identified in the majority of patients with unexplained pancreatitis. SOD represented the most common finding. Moderate to severe chronic pancreatitis was found in over one-fifth of these patients. Bile analysis, SOM, and EUS are useful tools in the evaluation of unexplained acute pancreatitis.
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