Classic chronic pancreatitis is associated with prior acute pancreatitis in only 50% of patients in a large single-institution study.

Background: The sentinel acute pancreatitis event (SAPE) hypothesis for pathogenesis of chronic pancreatitis (CP) postulates that acute pancreatitis (AP), especially recurrent AP (RAP), precedes development of CP. However, in a recent population-based study, 52/89 (58.4%) of CP had no prior episodes of AP. In a large clinic-based CP cohort, we aimed to determine the incidence and timing of prior AP in patients diagnosed with CP.

Methods: We retrospectively identified 499 consecutive patients with classic CP diagnosed at our institution from January 2013 through December 2015. We abstracted their demographic and clinical data, especially regarding prior AP.

Results: We identified 3 cohorts: 1) CP with no AP (n = 231 [46.3%]), 2) AP before CP (n = 250 [50.1%]), and 3) AP after CP (n = 18 [3.6%]). At CP diagnosis, 249 patients (49.9%) had no prior AP. Compared with the "CP preceded by AP" cohort, the "CP without AP"' cohort was older (59.2 ± 13.9 vs 48.6 ± 15.7 years; P < .001), had a higher prevalence of diabetes mellitus (30.3% vs 12.4%; P < .001), reported less pain (52.8% vs 87.6%; P < .001), and had a lower rate of endoscopic interventions (16.0% vs 39.2%; P < .001). In the "CP preceded by AP" cohort, 117 (46.8%) had a single episode of AP and 133 (53.2%) had RAP.

Conclusion: Nearly half the patients with classic CP did not have prior AP. Only a quarter of patients had CP that could potentially have evolved from prior RAP. Development of CP may be attributable to an altogether different pathogenesis (a non-SAPE pathway) for a considerable proportion of patients.