Background: The world’s first diagnostic criteria for early CP were proposed in 2009 in Japan. This study aimed to clarify the clinico-epidemiological features of early CP in Japan. Methods: Patients with early CP who were diagnosed according to the diagnostic criteria for early CP and had visited the selected hospitals in 2011 were surveyed. The study consisted of two-stage surveys: the number of patients with early CP was estimated by the first questionnaire and their clinical features were assessed by the second questionnaire. Results: The estimated number of early CP patients was 5410 (95% confidence interval 3675–6945), with an overall prevalence of 4.2 per 100,000 persons. The number of patients who were newly diagnosed with early CP was estimated to be 1330 (95% confidence interval 1058–1602), with an annual incidence of 1.0 per 100,000 persons. Detailed clinical information was obtained in 151 patients in the second survey. The male-to-female sex ratio was 1.32:1. The mean age was 60.4 and the mean age at disease onset was 55.4. Idiopathic (47.7%) and alcoholic (45.0%) were the two most common etiologies. Proportions of female and idiopathic cases were higher in early CP than in definite CP. Hyperechoic foci without shadowing and stranding were the most common findings on endoscopic ultrasonography. The clinical profiles of early CP patients who showed lobularity with honeycombing on endoscopic ultrasonography or previous episodes of acute pancreatitis were similar to those of definite CP patients. Conclusions: We clarified the current status of early CP in Japan.
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