Clinical Features of Thiopurine-Induced Acute Pancreatitis: Comparison Between Patients With and Without Inflammatory Bowel Disease.

Background and Aims: Patients with inflammatory bowel disease (IBD) are at increased risk of developing acute pancreatitis (AP). Thiopurines (TP) are a well-known cause of AP. The aims of this study were to compare the incidence of AP and TP-induced AP (TIP) between patients with and without IBD under the use of TP and to assess for risk factors of TIP. Methods: We examined a retrospective cohort of 664 patients treated with TP from 2016 to 2021 at our institution. AP was defined as pancreatitis confirmed by symptoms, serum tests, and radiology, and TIP as AP occurring shortly after starting TP and improving after withdrawal. We compared the incidence of AP and TIP between patients with and without IBD and reviewed the clinical features of TIP patients in detail. Results: There were 366 IBD patients and 298 without IBD. IBD patients included 249 males (52.4%) with a median age of 39 years. Among them, 211 had ulcerative colitis (UC) and 155 had Crohn's disease (CD). Azathioprine was administered to 560 patients, and 6-mercaptopurine to 104. AP occurred in 13 IBD patients but in none without IBD, with a significantly higher incidence in IBD patients (1.9% vs. 0%, Conclusions: TIP may be a condition specific to IBD. IBD patients with 5-ASA intolerance are prone to TIP.