The study aims at assessing the effectiveness of Diclofenac for prevention of post-ERCP pancreatitis. It will be undertaken embedded in the Swedish national register for Gallstone surgery and ERCP (GallRiks). Patients are randomised to Diclofenac prior to the ERCP or no prophylaxis. GallRiks is used to identify which patients fulfill the eligibility criteria and which patients develop pancreatitis after the ERCP.

Endoscopic Retrograde Cholangiopancreatography (ERCP) is a procedure commonly performed for diagnosing changes in the bile ducts or managing outflow obstruction. Although ERCP may in most cases be performed safely, there is a risk of developing acute pancreatitis following the procedure. The risk has been estimated to 5-10%, with an increased risk in women, younger patients and in case the cannulation is difficult.

Phospholipase 2 is crucial in the pathogenesis of acute pancreatitis. As Diclofenac is a potent inhibitor of Phospholipase 2, it has been suggested that it may be used for prevention of post-ERCP pancreatitis. There is some evidence for the effectiveness of Diclofenac, but more studies are needed to confirm that it reduces the risk of post-ERCP pancreatitis.

In order to test whether Diclofenac reduces the risk for post-ERCP pancreatitis, a register-based randomized controlled study is planned. The study will be conducted embedded in the Swedish Register for Gallstone Surgery and ERCP (GallRiks). GallRiks includes data corresponding to the eligibility criteria as well as outcome measures. GallRiks will also be used to record which patients have been screened for inclusion.

Patients who meet the eligibility criteria are invited to the study. If they accept inclusion, they are randomized to 100 mg Diclofenac prior to the ERCP or np prophylaxis. No blinding is done.

The aim is to include 1000 patients. When 500 patients have been included, an interim analysis will be performed, comparing the incidence of pancreatitis and mortality in the two groups. A retrospective review of the patient records will be performed for those who develop pancreatitis.

Inclusion Criteria:

• Patients undergoing ERCP

Exclusion Criteria:

• Decision to perform ERCP taken intraoperatively
• Intolerance/allergy against NSAID
• Patients taking NSAID daily
• Severe cardiac fail (ASA>4)
• Kidney failure (GFR<30 ml/min)
• Coagulation disorder
• History of peptic ulcer bleeding
• History of abdominoperineal resection
• Pregnancy
• Patients who do not understand Swedish