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Biliary cannulation in ERCP: you don’t need to be a shark if you now can be sharp!Referring to Liu WH et al. p. 1037–1042
Cannulation is the mainstay of endoscopic retrograde cholangiopancreatography (ERCP). Besides being the first step of ERCP, cannulation is actually often the most difficult step of the procedure and failure can preclude all the next steps. Several decades of ERCP as an established procedure, as well as the definition and implementation of training programs, have contributed to achieving a reference standard in ERCP competence, including cannulation rate, for which a minimum cutoff of ≥ 80 % is proposed by European Society of Gastrointestinal Endoscopy (ESGE) . However, a non-negligible rate of cannulation failure is still reported in clinical practice studies  . Cases of failure are mainly related to the morphology of the major papilla, the presence of a periampullary diverticulum, or pancreatic or ampullary cancer, and inexperience of the endoscopist . Moreover, it is worth considering that advanced cannulation techniques in cases of difficult cannulation carry a higher risk of post-ERCP pancreatitis (PEP), perforation, and bleeding . More recently, the evolution of cholangioscopy devices has allowed direct visualization of the bile duct during ERCP , just like colonoscopy did 50 years ago for direct visualization of the colon. Literature about the use of cholangioscopy has focused on the diagnostic assessment of indeterminate strictures, treatment of complex bile duct stones, and selective cannulation of complex biliary strictures   . No reports on the use of cholangioscopy for selective biliary cannulation have been published to date.
“This study might open a window for an easier, faster, and wireless biliary cannulation, as well as for radiation sparing during ERCP.”
In the study by Liu et al. in this issue of Endoscopy, a novel biliary cannulation technique under direct vision of a cholangioscope during ERCP (endoscopic retrograde direct cholangioscopy [ERDC]) is proposed . The authors explored the feasibility, success rate, adverse events, and learning curve of ERDC-guided cannulation in a selective cohort of patients with choledocholithiasis. The study is interesting for several reasons. First of all, the idea: this is the first study on this device and on its employment in biliary cannulation. The concept is similar to that of cholangioscopy-guided selective cannulation of complex strictures where, if you can see them, you can pass them. As for papillary cannulation, a limitation arose from the need to visualize the outlet of the biliary and pancreatic ducts in the virtual space just behind the papillary orifice; this has been overcome by the use of a small tapered and transparent cap fitted onto the tip of the cholangioscope, with which the inner fold of the papilla is pushed aside and the common tunnel is entered, uncovering the two separate duct orifices. Therefore, the authors have demonstrated the feasibility of ERDC for biliary cannulation, which was in fact the primary aim of the study.
A direct consequence of the technique is the possibility of obtaining cannulation without the need for X-rays, with the potential to limit radiology assistance for the entire ERCP. A reduction in the amount of radiation could be useful in specific clinical settings, such as pregnant women and young patients, as well as benefiting ERCP operators.
Another point of interest from this study is the first description of the anatomical difference between the biliary orifice, which is described as “petal-shaped,” and the pancreatic orifice, which is a “smooth channel.” From a training point of view, this could be very useful for endoscopists approaching ERCP to better understand the 2 D fluoroscopy-guided standard procedure and particularly the concept of axis alignment to obtain selective biliary or pancreatic cannulation.
A clear limit of the study is its small sample size. Despite enough numbers for a pilot study and to explore the feasibility of the new technique, the study does not allow the drawing of conclusions about efficacy and safety, which would also require there to be a control group.
It is worth mentioning the frequency of unintentional advancement of the guidewire into the pancreatic duct, with appears quite high (28.6 %) if we consider ERDC being proposed as a superselective biliary cannulation method. Additionally, this frequency did not change between the early and later stages of the study.
Another aspect to consider is that only a minority of patients had a periampullary diverticulum (14 %) or type 3 major papilla (29 %), which are classically associated with cannulation failure; other challenging cannulation situations, such as pancreatic or ampullary lesions, were even excluded from the study.
In conclusion, this study might open a window for an easier, faster, and wireless biliary cannulation, as well as for radiation sparing during ERCP. It provides a first morphologic description of the bile duct and pancreatic duct openings. The efficacy and safety of this new technique need to be further evaluated. In the era of evidence-based medicine, where clinical outcomes are at the heart of clinical practice, other studies are desirable to assess whether ERDC might provide real benefits over current techniques and therefore start to become widespread in training programs.
Further studies are also required in specific clinical settings, such as difficult biliary cannulation, to determine if ERDC can reduce the incidence of PEP and improve the cannulation rate, reducing the need for more demanding advanced cannulation techniques such as needle-knife precut. Of course, analyses about costs and environmental impact will also be warranted in order to assess the sustainability of this new technique.
Article published online:
18 September 2023
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