Objectives: To provide updated clinico-epidemiological information on chronic pancreatitis (CP) in Japan. Methods: We conducted a two-stage nationwide epidemiological survey; the number of CP patients was estimated in the first-stage survey, and their clinical features were examined in the second-stage survey. We surveyed patients with CP who had visited hospitals in 2016 and were diagnosed according to the Japanese diagnostic criteria 2009 (DC2009). Furthermore, we validated the new Japanese diagnostic criteria (DC2019) in patients with early CP diagnosed according to DC2009. Results: The number of patients with definite/probable CP in 2016 was 56,520 (prevalence, 44.5 per 100,000 persons), and that of early CP was 4470 (prevalence, 3.5 per 100,000 persons). We obtained detailed clinical information of 2150 patients with definite/probable CP and 249 patients with early CP. Compared with the early CP cases, the definite/probable CP cases had higher proportions of male (4.8 vs. 1.3), alcohol-related etiology (72.0% vs. 45.8%), smoking history (69.6% vs. 41.0%), diabetes mellitus (42.3% vs. 19.3%), and past history of acute pancreatitis (AP) (50.4% vs. 22.1%). Among the patients with early CP diagnosed according to DC2009, 93 (37.3%) were diagnosed with early CP according to DC2019, but the diagnosis of the remaining 156 (62.7%) patients was downgraded. Alcohol-related etiology, smoking history, early disease onset, and past history of AP were associated with the maintenance of early CP diagnosis in DC2019. Conclusion: We clarified the current status of CP in Japan. Further validation studies are warranted to clarify the diagnostic utility of DC2019.
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