Predicting native papilla biliary cannulation success using a multinational Endoscopic Retrograde Cholangiopancreatography (ERCP) Quality Network

Predicting quality is an important part of determining training, credentialing, and recredentialing thresholds. Endoscopic retrograde cholangiopancreatography (ERCP) is widely performed to diagnose and treat pancreatic and biliary disorders, at 1 per 1000 population, estimated at 3–500,000 annually in the US. Post-ERCP pancreatitis is the most common adverse event (1% to 7%, up to 10-20% in high risk patients) [1‐4], accounts for most of the related mortality (0.1%), an estimated 500 deaths/year in the US [5, 6]. Pancreatitis is more likely after repeatedly failed cannulation [7], thus maximizing cannulation success is important, not only for avoiding costly repeat and rescue procedures, but also for decreasing adverse events.

In community practice, ERCP is most often performed for biliary diseases [8], with the rate of successful biliary cannulation remaining the key performance metric. Minimum standards of 80-90% have been proposed internationally [9, 10], yet wide practice variations (54%-98%) exist. This rate variation can only be partly explained by variable exclusions of precut sphincterotomy, and cut/stented papillae [11‐14]. Although “pre-cut” sphincterotomy to facilitate access in difficult cases may increase risk in inexperienced hands, recent meta-analyses of randomized trials concluded that precut appears safer than persistence for experienced endoscopists [15]; and may arguably no longer be regarded as “failure”, at least as a secondary outcome. It would also seem preferable to exclude previously stented/cut papillae.

Volumes, training, and practice conditions may play a role [16, 17], yet these factors have not consistently been strong predictors [8]. Difficulty of the procedure may also contribute [18, 19]. The influence of other factors (trainees, comorbidity, sedation) remains largely unknown. Therefore, data gathered in a unique multinational ERCP Quality Network, were used to investigate the predictors for native papilla biliary cannulation success (with and without “precut”) using multilevel logistic regression analyses.

In the Network, 13,018 ERCPs in native papillae were performed by 85 endoscopists. Qualifying endoscopists (contributing >30 cases), consecutively entered a median of 8.9 ERCP/week (range 5–27) over up to almost 3 years (median entry 80 days). Although consecutive entry was not able to be audited directly, each endoscopist’s actual entered case volume was higher than their respective expected case volume for this time frame (using annual volume at baseline survey), consistent with consecutive case entry. Conventional deep biliary cannulation success rate was 89.8% (ranging 63.9%-100% for different endoscopists). Precut sphincterotomy was performed in 876 (876/13018, 6.7%) ERCPs, and deep biliary cannulation was achieved in 745 (85.1%). Overall deep biliary cannulation success rate (including precut-assisted cases) was 95.6% (ranging 80.2%-100% for different endoscopists).

A conventional cannulation success rate threshold of 80% was exceeded by 73 (85.9%) endoscopists, and 90% by 42 (49.4%) endoscopists. An overall (including precuts) cannulation success rate threshold of 80% was exceeded by all endoscopists, and 90% by 71 (83.5%).

Deep biliary cannulation success in native papillae is a widely accepted measure of competence in ERCP during training, and quality of an endoscopist in ERCP practice. Identifying predictors for successful biliary cannulation in native papilla, both at a case- and at an endoscopist-/team-level, have important implications in improving the quality of ERCP and patient care. Further multivariate analyses suggest that only case-specific factors are significantly associated with conventional native papilla biliary cannulation success, and that endoscopist- and institution-level factors may not be as important.

Pre-procedure evaluations considering complexity and indications are important, to weigh anticipated success rates into decision-making and consent. Prior studies correlating higher difficulty score and lower success were heterogeneous without sufficient adjustment for confounders; Verma et al. found no correlation between conventional cannulation success and procedure difficulty for trainees [21]. Our results supported a relationship, although the absolute differences seen were small. Overall “case” complexity and difficulty is determined by many factors (of which cannulation is just one), and so, does not necessarily correlate with “cannulation” difficulty. The negative randomized trials of ERCP in mild to moderate acute gallstone pancreatitis should already limit its use in active pancreatitis due to limited efficacy [22]; but pancreatitis also predicted lower success rates in our study, perhaps related to duodenal edema, providing more reason to avoid this context. Obstructive jaundice (mostly cancers) predicts lower success than in suspected stone cases; this is in keeping with a recent randomized trial advising against ERCP in obstructive jaundice from surgically resectable tumors mostly because of morbidity related to cannulation/stenting failures and rescue procedures (69%/83% success in drainage at ERCP in community/academic centers, respectively) [23]. Post-surgical biliary issues (e.g. leaks, strictures) also predict lower success; this has not been previously reported; anatomic distortion, edema, or need for atypical positioning (e.g. supine) because of surgical wounds may contribute.

Trainee involvement (modeled as yes or no) has been shown to increase post-ERCP pancreatitis [24]. The British Society of Gastroenterology (BSG) study reported trainees reduced cannulation success to 54% [12]. However, we explored the proportion of involvement, and found conventional and precut-assisted cannulation success rates decreased only with more casual trainee involvement. Trainees with brief involvement in a case may cause papilla edema, and lower the chance of the supervisor’s success. Lastly, confounding could exist if more skilled endoscopists allowed more trainee hands-on time.

In the present study, high ASA score was surprisingly another factor predicting lower cannulation success. Tenuous sedation (requiring a more hurried procedure) or patient positioning (e.g. due to obesity) may hinder cannulation in some way. Our results suggest that outpatient ERCP, adjusted for other factors, may have a higher success rate, even though adverse event rates may be comparable [25, 26]. Previous reports have found higher technical success rates achieved under deep sedation and general anesthesia than moderate (“conscious”) sedation because of better patient tolerance and compliance [27, 28]. However, our results showed that deeper sedation only predicted success if precut was allowed; this may be explained by an improved ability to use advanced rescue techniques with deeper sedation. Country predicted success in univariate analysis, but when corrected for differences in sedation use and other factors, it did not; the univariate association is likely confounded by international sedation practice differences.

ASGE, based on learning curves, recommends at least 180–200 cases (at least 50% therapeutic) to achieve competency in cannulation [9]. A recent study, however, found that at least 350 supervised procedures were needed for an 80% native papilla biliary cannulation success rate [21]. In the ERCP network, 69.5% endoscopists received <200 procedures during their training (54.2% less than 100), comparable to a recent survey: 60.4% responders completed <180 training cases [29]. Training volumes did not predict cannulation success in our cohort. However, high-volume-trained endoscopists (>500) were under-represented; higher-volume training might have impact. Another consideration is that endoscopists with <200 cases in training tended to have higher years performing ERCP (data not shown); as such, their learning curve may have already risen and plateaued in practice, minimizing the apparent impact of their lower volume training.

Many believe that after proper training, experience (volume, years) and annual volume contribute to outcomes, but consensus on relative importance of annual volume vs cumulative experience, and on recredentialing volume thresholds, is lacking. The British Joint Advisory Group (JAG) recommends that endoscopists should perform >75 ERCPs/year [30]. Both an American [11] and Austrian study showed that >50 ERCPs/year had higher cannulation success [31], yet community endoscopists (median 50 ERCPs/year) demonstrated no associations between success and volume or experience [8]. Weaknesses of the above mentioned studies include the lack of separating out cannulation success with and without precut, or native vs cut/stented papillae. Our data showed that higher annual volume (using quartiles) had a small but nonsignificant trend toward higher conventional success and a significant trend toward overall (precut-allowed) success (>239 ERCP/yr: OR 2.79). Perhaps some of the higher overall success of the more active endoscopist might be due to their ability to comfortably use a more advanced rescue technique like precut sphincterotomy. We explored other cutoffs for annual volume (data not shown), including 50 as others have suggested, and 100; neither was significant.

Fluoroscopy time can be influenced by several procedural factors, as well as endoscopist and X-ray technician experience, trainee involvement, and equipment quality [32‐35]. Being a radiation-efficient endoscopist (averaging ≤ 3 min use in grade-1 cases) predicted overall success, suggesting quality in one aspect of practice might be associated with quality in another, which is a novel concept.

In conclusion, our results based on this unique international dataset indicate that case-specific factors may have greater impact on the most important ERCP quality metric (biliary cannulation success), than endoscopist-specific ones. Annual volume and sedation practices may influence ultimate success when precut-assisted success is not considered a failure. With regard to endoscopist experience factors, annual volume appears to perhaps be more important than prior experience, and the ideal volume (>200/year) may be considerably higher than the 50/year previously published. Further study, with an even larger number of endoscopists, could further explore the minimum annual volume for maintenance of ERCP competence.