Trends and clinical characteristics of pediatric acute pancreatitis patients in Japan: A comparison with adult cases based on a national administrative inpatient database

Background: /Objectives: Pediatric acute pancreatitis (AP) is not as rare as previously thought, and an increased incidence thereof has been reported. We aimed to clarify the trends and clinical characteristics of pediatric AP in Japan. Methods: We utilized the Japanese Diagnosis Procedure Combination inpatient database for patients admitted between April 2012 and March 2021, and extracted the data of patients whose principal diagnosis was AP (ICD-10 code K85) or in whom AP accounted for most of the medical expenses. Patients were classified into pediatric (≤18 years) and adult (age >18 years) groups. Results: We included 3941 AP cases in pediatrics and 212,776 in adults. AP cases accounted for 0.08 % of all admissions in pediatrics and 0.33 % in adults, with upward trends during the study period. The proportion of AP patients among all admissions was increased with advancing age in pediatrics. Compared to adults, pediatric AP patients had a smaller proportion of severe cases (22.9 % vs. 28.7 %; P < 0.001), fewer interventions for late complications (0.2 % vs. 1.3 %; P < 0.001), shorter hospital stays (mean 16.6 days vs. 18.0 days; P = 0.001), lower overall mortality (0.7 % vs. 2.9 %; P < 0.001), and lower mortality in severe cases (1.3 % vs. 5.6 %; P < 0.001). Pediatric cases were more frequently transferred from other institutions and treated at academic hospitals than adults (both P < 0.001). Conclusions: There was an upward trend in the proportion of AP among all admissions in pediatrics, with a lower risk of complications and mortality than adult cases.