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
. 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
; 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)
. 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
. The British Society of Gastroenterology (BSG) study reported trainees reduced cannulation success to 54%
. 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
. A recent study, however, found that at least 350 supervised procedures were needed for an 80% native papilla biliary cannulation success rate
. 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
. 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
. Both an American
 and Austrian study showed that >50 ERCPs/year had higher cannulation success
, yet community endoscopists (median 50 ERCPs/year) demonstrated no associations between success and volume or experience
. 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.
There are limitations with our study. First, as stated above, we have lower power to detect the effects of some doctor-level factors on biliary cannulation success due to the modest number of endoscopists. Second, the self-reported data could not be audited for accuracy; however the anonymous design should have reduced bias. Despite this, we acknowledge there could have been some selective reporting of more successful procedures; the number of procedures entered appeared to be similar to the number expected for each provider (based on a priori reported volumes), so we hope this bias was minimal. In addition, the generalizability of our conclusions may be limited by the fact that the volunteering endoscopists may not reflect average ERCP practice worldwide; however, this more pertains to the overall success rates, and less likely to affect the generalizability of the predictors themselves. Fortunately, the spectrum of training, volume, years in practice, practice settings, and success rates are comparable to that of other studies, and does not suggest a homogenous, highly skilled cohort of tertiary clinicians.