This study is a single-center, randomized, single-blind, parallel controlled clinical study to explore the optimal dose of postoperative indomethacin suppository for the prevention of post-ERCP pancreatitis. The purpose of this study is to explore the optimal dosage of indomethacin suppository for PEP prevention, to study the control effect of indomethacin on hyperamylaseemia, and to further explore the group of patients who benefit most from this therapy.

This is a single-centre, randomized, single-blind, parallel-controlled designed clinical study to explore the optimal dose of postoperative indomethacin suppository for the prevention of post-ERCP pancreatitis. The study will enroll 192 patients who undergo ERCP in the Department of Gastroenterology of the First Affiliated Hospital of Soochow University from November 2022 to October 2023, and they will be randomly assigned to 3 groups of 64 each according to the date of surgery and hospitalisation number in a random number list formed by SPSS software.

Inclusion Criteria:

• According to the "Chinese ERCP Guidelines (2018 Edition)", patients with various biliary and pancreatic diseases who have indications for ERCP examination and treatment, who are at least 18 years old and have no contraindications, and who can tolerate the examination;
• Preoperative blood coagulation function, liver and kidney function indicators are in the normal range;
• The patients agreed to participate in this experiment, signed the informed consent form, and was approved by the hospital ethics committee.

Exclusion Criteria:

• Contraindications to indomethacin and other NSAIDs: such as allergy to indomethacin, severe heart failure, active peptic ulcer/bleeding, perioperative period of coronary artery bypass surgery, etc.;
• There are severe cardiovascular and cerebrovascular diseases, respiratory insufficiency and coagulation dysfunction, etc., and cannot tolerate ERCP examination;
• Those who have recently used indomethacin and other non-steroidal anti-infective drugs;
• Pregnant or lactating women.