Background of research

Pancreatitis is the most common complication after Endoscopic retrograde cholangiopancreatography (ERCP). It occurs in approximately 5% of patients. The risk can approach 20 to 30% in those with known pre- and intra-procedural risk factors. Three in 100 patients with post ERCP pancreatitis (PEP) consequently die. The placement of pancreatic duct stent and the use of rectal administered indomethacin have both been independently shown to reduce PEP. The placement of a pancreatic duct stent has been for a long time considered the gold standard in the prophylaxis against PEP. In a meta-analysis of 8 RCTs that compared the use of pancreatic duct stents to no treatment, pancreatic duct stenting in high risk patients reduces incidence of PEP by approximately 5 fold. In a landmark study by Elmunzer et al., rectal administered indomethacin was shown to reduce PEP (52 of 307 patients,16.9% to 27 of 295 patients, 9.2%, P=0.005). In the trial, \>80% received pancreatic duct stents in addition to rectal indomethacin. Overall there have been 7 RCTs on the use of rectal indomethacin all showing benefits with its use, 3 with PDS and 4 without. In the literature, there has been no direct comparison between the use of rectal indomethacin alone and insertion of PDS. In a secondary analysis of the trial by Elmunzer et al., PEP following the use of rectal indomethacin alone was less compared with the placement of PDS. In a meta-analysis by Akbar et al. pooling 29 studies (22 PDS and 7 indomethacin), the use of rectal indomethacin alone was associated with fewer PEP when compared to insertion of PDS on an indirect comparison using network metaanalysis (OR 0.48, 95%CI 0.26-0.87). The more favorable results with rectal indomethacin alone raised the question if PDS insertion is necessary. Furthermore, in another secondary analysis, patients after failed PDS insertion had a 34.7% rate of pancreatitis. In contrary, the rate of pancreatitis was 16.4% in those after successful PDS and 12.1% after no attempt at PDS insertion. The SVI (stent versus indomethacin) trial (NCT024762279) by the US cooperative for Outcomes Research in Endoscopy (USCORE) group is an ongoing non-inferiority trial that compares indomethacin alone to the combination of indomethacin and PDS in 1430 high risk patients with the primary outcome of pancreatitis. The trial tests the hypothesis that PDS is no longer necessary in the context of rectal indomethacin.

The rationale for the trial has been based on the secondary analysis of the Elmunzer trial and the network analysis aforementioned.

The investigators argue that the relative merits of rectal indomethacin and PDS placement have not been established. There may have been substantial difference in the baseline risks between the trials using either rectal indomethacin and PDS placement alone. The small number of RCTs over the use of rectal indomethacin may have overestimated its beneficial effect especially among patients at lower risk of PEP. A direct comparison in the form of a RCT to compare effectiveness of both treatment modalities is required. The insertion of PDS may continue to be important in patients contraindicated for the use of NSAIDs.

Research plan and methodology The investigators hypothesize that rectal administration of indomethacin is not inferior to placement of a pancreatic duct stent in the prevention of pancreatitis after ERCP in high risk patients. In patients randomised to receive pancreatic duct stents, the investigators sought to determine the success rate with PDS insertion and outcomes following successful or unsuccessful PDS insertion. In addition, the investigators analyse possible factors to PEP in both cohorts of patients on either indomethacin or PDS.