If surgical treatment is not possible in patients with malignant obstruction in the common bile duct, placing metal stents using endoscopy is a standardized treatment to resolve biliary obstruction. The metal stent is located in the bile duct to cover the stenotic portion by malignant tumors.

The lower end of the metal stent can be located inside the common bile duct above the major ampulla or in the duodenum through the major ampulla. These two procedures with supra- or trans-papillary stents are currently being performed in general clinical practices, depending on the preference of the endoscopists. Until now, the comparison of the clinical results of the two procedures has been scarcely studied, and there is no prospective study yet. Therefore, researchers aim to compare the clinical results of two stent procedures through prospective randomized controlled studies.

If surgical treatment is not possible in patients with malignant obstruction in the common bile duct, endoscopic metal stent placement to resolve biliary obstruction is a standard treatment that is commonly performed. The metal stents relieve the bile duct stenosis by malignant tumors, helping to drain the bile and improving jaundice. There is no doubt that the center of the metal stent is located in the central part of the biliary stricture, but the location of the lower end of the metal stent is not fixed. The lower end of the metal stent can be located in two main locations, either in the common bile duct above the major ampulla or in the duodenum through the major ampulla. These procedures with supra- or trans-papillary stents are performed in common and are determined by the operator's preference.

According to several retrospective studies so far, trans-papillary metal stents were effective in improving the initial biliary obstruction, but there was no difference in their long-term effects. Mao et al. showed that trans-papillary metal stents increase jaundice-free survival, and Shin et al. revealed the advantages of trans-papillary metal stents because they had a high success rate of secondary endoscopic procedures. On the contrary, Okamoto et al. showed that acute cholangitis more developed after trans-papillary metal stents placement, while Joe et al. revealed the advantages of supra-papillary metal stents because they reduce acute pancreatitis after the procedures. It has not yet been determined which method is effective. So far studies are all retrospective, and some of them placed the metal stents in a percutaneous way rather than endoscopy without sphincterotomy. Besides, some studies included intra-hepatic or hilar bile duct strictures, making it difficult to interpret the results.

Therefore, through a prospective randomized controlled study, the researchers want to compare the clinical results of supra- and trans-papillary metal stents placed by endoscopes in malignant common bile duct obstruction.

Inclusion Criteria:

• patients with common bile duct obstruction due to malignancy

Exclusion Criteria:

• intrahepatic or perihilar bile duct obstruction (except Klatskin type I)
• patients who have operability or want surgery
• strictures located within 2 cm from the end of distal common bile duct
• patients who are not able to undergo endoscopy due to cardiovascular or pulmonary diseases
• patients whose informed consents are not received
• patients in whom an endoscope can not access to the ampulla due to anatomical deformity by previous surgery

All of the individual participant data collected during the trial, after deidentification.

Immediately following publication. No end date

• Investigators whose proposed use of the data has been approved by an independent review committee
• To achieve aims in the approved proposal
• Proposals may be submitted up to 36 months following article publication.

Assigned groups are secreted to the participant and outcome assessors