Aim: The overall aim of this thesis was to study risk factors for and strategies to prevent complications of Endoscopic Retrograde Cholangiopancreatography (ERCP). 

Methods: Prospectively registered data from the Swedish National Quality Register for Gallstone Surgery and ERCP (GallRiks) 2006-2018 were retrospectively retrieved and reviewed. In Study I, ERCP procedures performed for common bile duct stones (CBDS), were analysed and cross-checked with the National Patient Register (NPR) in order to assess risk factors for post-ERCP pancreatitis (PEP). In Study II, different techniques for CBDS clearance over time at different hospital levels and the effectiveness and safety of postoperative rendezvous ERCP compared to intraoperative rendezvous ERCP were studied. In Study III, the rate of postoperative cardiovascular events in CBDS-patients treated with ERCP only, cholecystectomy only, cholecystectomy followed by delayed ERCP, cholecystectomy together with ERCP, or ERCP followed by delayed cholecystectomy were analysed. In Study IV, associations between ERCP success and complications, and endoscopist- and centre case-volumes regarding procedures for CBDS, and suspected or confirmed malignancy were analysed. 

Results: Women, patients<65 years, patients with hyperlipidaemia, and those with a previous history of recent acute pancreatitis had a higher risk for PEP, while patients with diabetes had a lower risk (all p<0.05). Intraoperative ERCP increased during the period of the study, whereas preparation for postoperative ERCP decreased. CBDS management differed between different hospital levels. Total rate of intra- and postoperative complications as well as intraoperative bleeding, postoperative bile leakage, and postoperative infection with abscess were higher in the postoperative rendezvous ERCP group (all p<0.05). However, PEP, postoperative bleeding, cholangitis, percutaneous drainage, antibiotic treatment, ICU stay, readmission/reoperation within 30 days, and 30-day mortality did not differ between the groups. Nor did risk for cardiovascular complication or death within 30 days differ between patients treated for CBDS by cholecystectomy and/or ERCP. A high endoscopist case-volume was associated with higher successful cannulation rate and lower PEP rate (p<0.05). Centres with a high annual case-volume were associated with higher successful cannulation rates (p<0.05). 

Conclusions: Age, sex, hyperlipidaemia, and previous history of recent acute pancreatitis all increased the risk for PEP while diabetes reduced the risk. Techniques for management of CBDS discovered at cholecystectomy have changed over time and differ between hospitals levels. Though intraoperative rendezvous ERCP is the method of choice, postoperative rendezvous ERCP is an acceptable alternative when adequate ERCP resources are lacking or limited. Primary ERCP as well as cholecystectomy for CBDS may be performed with acceptable safety. Higher endoscopist- and centre case-volumes lead to safer and more successful ERCP.