It is now established that indomethacin, a non-steroidal anti-inflammatory drug, at a dose of 100 mg, is effective in reducing the frequency and severity of pancreatitis (inflammation of the pancreas) after endoscopic retrograde cholangiopancreatography (ERCP) in high risk patients. However, the optimal dose required is not known. The purpose of this study is to determine whether a dose of 200 mg, administered as rectal suppositories, is more effective than the standard dose of 100 mg. An ERCP procedure is a scope procedure where a lighted tube with a camera is passed down the patient's throat and allows for evaluation of the bile duct and/or pancreatic duct. The most common side effect of this procedure is post-ERCP pancreatitis, or swelling of the pancreas. Some patients are at higher risk for this complication than others. Our hypothesis is to compare the efficacy of these two dose regimens (100 mg vs 200 mg) of prophylactic rectally-administered indomethacin on the frequency and severity of post-ERCP pancreatitis in high-risk patients.