Reply to Kawakami et al.

Guidewire-assisted cannulation should be used as first-line cannulation technique to increase biliary cannulation success and prevent post-ERCP pancreatitis

We would like to thank Dr. Kawakami and his group for their response to our recent article [1]. While we agree with several of the points made, we feel that some of the issues were overstated.

First, we disagree with the statement that “the incidence of PEP does not depend on the type of cannulation procedure used, but on the proficiency level of the endoscopist employing the cannulation technique.” There are many factors that affect the risk of pancreatitis after endoscopic retrograde cholangiopancreatography (post-ERCP pancreatitis, PEP), and data do not support the contention that the experience of the clinician is the most important determinant of complications. Interestingly, operator experience was not found to be a significant factor in determining biliary cannulation success or PEP in the recent randomized study by Dr. Kawakami and his group [2]. Numerous large prospective studies have identified a number of patient-related, procedure-related, and operator-related risk factors for PEP [3 – 6]. In particular, cannulation techniques have long been recognized to be important in causing PEP [3] and are obviously important for successful cannulation.

Second, we fully agree with the view that caution should be exercised before generalizing results from single-center studies involving one or two operators to wider practice. Such studies are inherently biased due to operator preference and level of expertise in a particular technique. While this assumption of limited generalizability is generally true when considering individual studies, systematic reviews of the literature consider all available data and thereby reduce the concern regarding generalizability [7]. Based on a comprehensive and systematic review of the literature with the inclusion of both multicenter (n = 5 with 1442 patients) and single-center studies (n = 7 with 2008 patients), our meta-analysis found that the guidewire-assisted cannulation technique significantly reduced PEP (risk ratio [RR] 0.51, 95 % confidence interval [CI] 0.32 – 0.82), increased primary cannulation success (RR 1.07, 95 %CI 1.00 – 1.15) and reduced the need for precut sphincterotomies (RR 0.75, 95 %CI 0.60 – 0.95) compared to the contrast-assisted cannulation technique. Although it is unlikely that biliary cannulation is performed with either technique alone in clinical practice, our results support the use of the guidewire-assisted technique as the most appropriate first-line primary cannulation technique, especially when guidewires have become essential in maintaining ductal access in the era of therapeutic ERCP.

Third, “crossover” between interventions is not uncommon due to unforeseen technical challenges or endoscopic findings in clinical practice. However, the “crossover” effect in a clinical trial can substantially reduce the statistical power to find an overall treatment difference in the overall efficacy of the intervention, or distinguish beneficial or harmful effects related to the intervention. Despite the fact that the inclusion of “crossover” studies may have diluted the treatment effect of the guidewire-assisted technique for the prevention of PEP in our meta-analysis, a significant reduction of the risks of PEP was still found with the guidewire-assisted technique. We agree that a combination of cannulation techniques with a flexible approach should be adopted in clinical practice, particularly in relation to anatomical factors. Nevertheless, the results of our meta-analysis (with the inclusion of both “crossover” and “non-crossover” studies) strongly support the use of the guidewire-assisted technique as the first-line cannulation technique, but if this fails, alternative techniques should be applied to avoid the potential adverse consequences of failed ERCP.

Finally, we read with interest the randomized controlled trial published by Dr. Kawakami on the 15° backward-oblique angle duodenoscopes (BOADs) vs. 5° BOAD using wire-guided cannulation technique [8]. Although 15° BOADs are mainly used in Japan, 5° BOADs are mostly used in the rest of the world. Therefore, larger clinical trials of 15° BOADs conducted outside of Japan are needed to establish their clinical efficacy in improving the success of biliary cannulation and reducing the risk of PEP.

• References

• 1 Tse F, Yuan Y, Moayyedi P et al. Guide wire-assisted cannulation for the prevention of post-ERCP pancreatitis: a systematic review and meta-analysis. Endoscopy 2013; 45: 605-618
• 2 Kawakami H, Maguchi H, Mukai T et al. A multicenter, prospective, randomized study of selective bile duct cannulation performed by multiple endoscopists: the BIDMEN study. Gastrointest Endosc 2012; 75: 362-372, 372
• 3 Freeman ML, DiSario JA, Nelson DB et al. Risk factors for post-ERCP pancreatitis: a prospective, multicenter study. Gastrointest Endosc 2001; 54: 425-434
• 4 Wang P, Li ZS, Liu F et al. Risk factors for ERCP-related complications: a prospective multicenter study. Am J Gastroenterol 2009; 104: 31-40
• 5 Testoni PA, Mariani A, Giussani A et al. Risk factors for post-ERCP pancreatitis in high- and low-volume centers and among expert and non-expert operators: a prospective multicenter study. Am J Gastroenterol 2010; 105: 1753-1761
• 6 Cheng CL, Sherman S, Watkins JL et al. Risk factors for post-ERCP pancreatitis: a prospective multicenter study. Am J Gastroenterol 2006; 101: 139-147
• 7 Mulrow CD. Rationale for systematic reviews. BMJ 1994; 309: 597-599
• 8 Kawakami H, Maguchi H, Hayashi T et al. A prospective randomized controlled multicenter trial of duodenoscopes with 5 degrees and 15 degrees backward-oblique angle using wire-guided cannulation: effects on selective cannulation of the common bile duct in endoscopic retrograde cholangiopancreatography. J Gastroenterol 2009; 44: 1140-1146