Chronic pancreatitis without prior acute pancreatitis: Is it a different disease?

Background Recent studies report that a significant proportion of patients diagnosed with chronic pancreatitis (CP) did not have a preceding clinically diagnosed episode of acute pancreatitis (AP). We used a multicenter cohort study to examine the distribution and associated factors for CP without prior AP (CPNAP). Methods Demographic, clinical, radiologic, interventional and outcome data recorded at enrollment from participants in the PROCEED study were examined. Information about prior, concomitant, and subsequent AP, including the interval between prior AP and subsequent CP, along with number of episodes of AP were examined. Continuous variables (medians and ranges) with Kruskal-Wallis test and multiple logistic regression analysis were performed to identify associations with CPNAP vs CPAP (CP without prior AP). Results Of the 642 participants with known dates of CP diagnosis and status of AP, 311 (48%) were classified as CPNAP. CPNAP and CPAP groups were different from each other regarding demographic, clinical, and imaging features. Participants who had AP at a younger age progressed to subsequent CP over a longer period compared to those who had AP at an older age. Such slower progression to CP in young onset AP did not differ between alcohol and non-alcohol etiologies. Logistic regression analysis demonstrated that CPNAP group is associated with older age, and less often with alcohol as risk factor, presence of intermittent as well as constant severe pain, and pancreatic duct stricture. Conclusions Almost half of the patients with CP do not have one or more antecedent AP episode. There are differences in demographic, clinical, and imaging features between CPNAP and CPAP, suggesting these may represent different disease subtypes.