The Epidemiology of Idiopathic Acute Pancreatitis, Analysis of the Nationwide Inpatient Sample From 1998 to 2007

Objective: The study aimed to better define the epidemiology of idiopathic acute pancreatitis (IAP). Methods: We identified admissions with primary diagnosis of acute pancreatitis (AP) in Nationwide Inpatient Sample between 1998 and 2007. Idiopathic AP was defined as all cases after excluding International Classification of Diseases, Ninth Revision, codes for other causes of AP (including biliary, alcoholic, trauma, iatrogenic, hyperparathyroidism, hyperlipidemia, etc). Results: Among the primary admissions for AP, 26.9% had biliary pancreatitis, 25.1% alcoholic, and 36.5% idiopathic. Idiopathic AP had estimated 81,8025 admissions with a mean hospitalization of 5.6 days. Patients with IAP accounted for almost half of the fatalities among the cases of AP (48.2%) and had a higher mortality rate than both patients with biliary pancreatitis and patients with alcoholic pancreatitis (1.9%, 1.5%, and 1.0%, respectively, P < 0.01). Forty-six percent of patients with biliary pancreatitis underwent cholecystectomy during the index hospitalization, compared with 0.42% of patients with IAP. Patients with IAP had a demographic distribution similar to that of patients with biliary AP (female predominant and older), which was distinct from patients with alcoholic pancreatitis (male predominant and younger). There was a gradual but steady decrease in the incidence of IAP, from 41% in 1998 to 30% in 2007. Conclusions: Despite improving diagnostics, IAP remains a common clinical problem with a significant mortality. Standardization of the clinical management of these patients warrants further investigation.