Double Guidewire Research Articles

A Comparative Study of Transpancreatic Sphincterotomy, Double Guidewire Technique, and Precut Sphincterotomy in Difficult Naive Biliary Cannulations in a Tertiary Care Center in Western India

Abstract Introduction Difficult biliary cannulation leads to prolonged papillary manipulation and repeated attempts at cannulation are known to increase the risk of postendoscopic retrograde cholangiopancreatography (ERCP) pancreatitis. This study aims to compare the efficacy and complications of three rescue methods, transpancreatic biliary sphincterotomy (TP), double guidewire technique (DGW), and precut sphincterotomy (precut) in difficult common bile duct (CBD) cannulations. Methods Seventy-six patients (>18 years of age) with a native papilla undergoing ERCP for biliary cannulation were recruited. Those who had inadvertent pancreatic duct cannulations (>1) were included. A pancreatic stent was inserted in all cases. They underwent either DGW (n = 25), precut (n = 25), or TP (n = 26) as rescue methods and were compared in terms of the success of cannulation and post-ERCP complications. Results Of the total 76 cases, 82% were for benign indications, the most common being choledocholithiasis (69.7%). Jaundice was noted in 52% (n = 13/25), 60% (n = 15/25), and 38.5% (n = 10/26) of the DGW, precut, and TP cases, while 40% (n = 10/25), 12% (n = 3/25), and 30.8% (n = 8/26), respectively, were in cholangitis at presentation. The most common type of papilla was type 1 overall and each subgroup. While successful cannulation was achieved in 88.5% (n = 23/26) of TP and 84% (n = 21/25) of the DGW group, only 64% (n = 16/25) of the precut cases were cannulated. Three (n = 3/25) cases had mild bleeding and two mild pancreatitis, one severe pancreatitis, and one perforation were recorded in the precut group. One patient each had severe and mild pancreatitis in the DGW group, while one had mild pancreatitis and two had moderate pancreatitis in the TP group. All the patients were managed conservatively. Conclusion There was no significant difference in the technical success rate (p = 0.075) as well as complications (p = 0.117) between the three salvage methods for difficult naive CBD cannulations.

Transpancreatic Sphincterotomy After Double Guidewire Technique Was Noninferior to Primary Transpancreatic Sphincterotomy in Difficult Biliary Cannulation.

When unintentional pancreatic duct access occurs during difficult biliary cannulation, the double guidewire (DGW) or transpancreatic sphincterotomy (TPS) may be utilized. DGW can be easily switched to TPS due to the existing guidewire in the pancreatic duct. However, the efficacy of TPS after DGW, named sequential DGW-TPS technique, versus primary TPS has not been assessed. Our aim was to compare the benefits and adverse events of sequential DGW-TPS technique and primary TPS. We performed a comparative retrospective cohort study that enrolled a total of 117 patients with native papillae. The patients were divided into one of 2 groups according to the primary bile duct access technique (sequential DGW-TPS or primary TPS), both with pancreatic stenting. Between November 2017 and May 2023, a total of 84 patients were grouped into sequential DGW-TPS and 33 into primary TPS. The overall post-ERCP pancreatitis (PEP) rate was 4.3% in the entire cohort, with no statistical differences were observed between the groups in terms of PEP rates (P = 0.927), PEP severity (P = 1.000), first biliary cannulation success (P = 0.621), overall cannulation success (P = 1.000), hyperamylasemia incidence (P = 0.241), elevated amylase levels (P = 0.881), and postoperative hospital stay (P = 0.185). Furthermore, these results remained consistent in multivariable regression analysis. The sequential DGW-TPS technique showed a comparable safety and biliary cannulation success rate to primary TPS in difficult biliary cannulation. Given the potential long-term complications associated with TPS, DGW should be first if inadvertent pancreatic access occurs, with TPS serving as second only if DGW fails.

Transpancreatic sphincterotomy with double guidewire and pancreatic prothesis after involuntary passage of the guidewire to the pancreas in attempts at biliary cannulation.

In this work we review the approach to difficult cannulation situations during ERCP. Among the known options to solve this problem, we suggest a technical variant that we believe can be useful to successfully complete ERCP with complication rates similar to a conventional ERCP, at least in our experience. To do this, we reviewed 1488 ERCPs and the 23 cases in which we applied this technical variant with its results and complications.

Endoscopic drainage of malignant distal biliary obstruction. Will ERCP no longer be necessary?

We read with interest the Editorial by Vila et al. on the paradigm shift for endoscopic biliary drainage of malignant distal biliary obstruction (MDBO) which places Endoscopic Ultrasound (EUS) drainage as the first option instead of traditional ERCP drainage. The modern biliary endoscopist must have the duodenoscope in one hand and the therapeutic echoendoscope in the other. ERCP training alone is no longer appropriate because the goal is to drain the obstruction during a single session. That is why in more and more centers the patient signs a single consent for endoscopic biliary drainage, whether by ERCP, EUS or combined. Should EUS drainage be used first for MDBO without attempting ERCP? A possible protocol for endoscopic drainage of MDBO could be to start with the duodenoscope for ERCP. If the papilla of Vater is accessible, try cannulation considering the ESGE criteria for a difficult cannulation: more than 5 contacts with the papilla; more than 5 minutes spent attempting to cannulate following visualization of the papilla; more than one unintended pancreatic duct cannulation or opacification. If biliary cannulation is not achieved, immediately switch to EUS drainage during the same session. Occasionally, the double guidewire technique or even transpancreatic biliary sphincterotomy could be used, but not needle-knife precut.

Unique double guidewire technique using a guidewire perforating the diverticulum for a difficult biliary cannulation.

Biliary cannulation of an intradiverticular papilla, classified type 1 as per the Li-Tanaka classification, is sometimes challenging [1]. Although in cases with difficult biliary cannulation the pancreatic duct guidewire placement technique is useful [2] [3], placing the guidewire in the pancreatic duct is sometimes difficult. We report a successful case of biliary cannulation in a patient with an intradiverticular papilla using an unusual double guidewire technique taking advantage of a guidewire perforating the diverticulum.

Morphology of the major duodenal papilla for the selection of advanced cannulation techniques in difficult biliary cannulation.

Morphology of the major duodenal papilla (MDP) influences the outcome of standard biliary cannulation. However, those data on advanced cannulation techniques are scarce. We aimed to study the impact of MDP morphology on the outcome of both standard and advanced cannulation methods. Images of naïve papilla were retrospectively reviewed and independently classified into 4 types (1: classic appearance, 2: small, 3: bulging, and 4: ridged papillae). All cannulation was started with guidewire cannulation. After failure, advanced cannulation including double guidewire (DG) and/or precut sphincterotomy (PS) was performed. Outcomes including success rate and complications were analyzed. A total 805 naïve papilla were included. The overall advanced cannulation rate was 23.2%. The MPD type 2 (OR 1.8, 95% CI 1.8-2.9) and type 4 (OR 2.1, 95% CI 1.1-3.8) required advanced cannulation technique at a higher rate than type 1. Type 3 significantly needed a higher proportion of PS when compared with type 1 (59.09% vs 27.03%, OR 3.90, 95% CI 1.51-10.06). Overall post-ERCP pancreatitis (PEP) was 8% and was not different among MDP types. PEP was significantly increased in difficult cannulation group (15.38% vs 5.71%, p-value < 0.001). Multivariate analysis demonstrated that DG independently increased risk of PEP (OR 3.6, 95% CI 2.0-6.6). MDP type 2 and type 4 were related to difficult cannulation. Although DG and PS can be used as advanced cannulation in all types, DG carries risk of PEP and PS may be preferred over DG in MDP type 3.

Does early application of needle-knife sphincterotomy (NKS) in patients with difficult biliary cannulation increase the risk of postERCP pancreatitis? A single centre study.

To determine that early needle-knife sphincterotomy does not increase post-ERCP pancreatitis in patients with difficult biliary cannulation as compared to standard cannulation. This prospective single-centre cohort study was carried out at Pak Emirates Military Hospital from January 2021 to June 2021. Patients requiring ERCP were enrolled in the study (according to inclusion and exclusion criteria) and were subsequently allotted different groups according to the technique used for deep biliary cannulation. Qualitative data was analysed using frequencies and chi square statistics whereas, quantitative data was analysed using mean±SD and one way ANOVA test. The cohort included 114 patients with 52.6% male patients and predominance of relatively younger age group (31-45 years). The most common indication for ERCP was choledocholithiasis (36%) with an overall technical success rate of 96%. Deep cannulation was achieved either through standard cannulation (56%), double guidewire and/or pancreatic stent assisted (10.5%), use of early Needle-Knife Sphincterotomy (19%), NKS as a last resort (3.5%) or Transpancreatic Stenting and/or combined sphincterotomy (6%). Pancreatitis as a complication occurred in 4(3.5%) patients, bleeding in 2(1.8%), on-table desaturation in 2(1.8%) and perforation in 1(0.9%) patient. The occurrence of pancreatitis was only related significantly to inadvertent PD cannulation through univariate and logistic regression analysis whereas, multiple cannulations (>5), gender, age, classification of papilla and the use of early NKS had no impact on pancreatitis or the occurrence of other complications. NKS is an effective and safe modality for deep biliary cannulation and achieving technical success where cannulation is deemed difficult and does not increase the risk of PEP if done by experienced endoscopists in high volume centres.

EUS-guided Rendezvous technique for the treatment of choledocholithiasis with difficult cannulation.

It is not uncommon to encounter difficult cannulation during endoscopic retrograde cholangiopancreatography (ERCP), most of which can be performed by double-guide wire, pre-cut and other techniques. Endoscopic ultrasound-guided biliary drainage (EUS-BD) can be used as a remedial solution for ERCP failure. This article provides a very well experience in ERCP combine with EUS-RV technique in cases where the duodenal papilla is located above the medial diverticulum. At the same time, some skills of EUS-RV are provided for endoscopists.

Suprapapillary Needle Knife Fistulotomy Versus Conventional Precut Sphincterotomy in Difficult Biliary Cannulation: A Retrospective Comparative Study.

Endoscopic retrograde cholangiopancreatography (ERCP) is an important therapeutic tool for many biliary diseases. Selective biliary cannulation is the first step of the treatment process. Needle knife fistulotomy (NKF) and conventional precut sphincterotomy (CPS) are widely used in difficult biliary cannulation. However, there are different results in their effectiveness and safety. This study aimed to compare both methods regarding cannulation success and adverse event profile. All eligible consecutive patients with naive papillae who underwent biliary ERCP by a single experienced endoscopist over a 3-year period were included retrospectively. The standard cannulation method with a guidewire-loaded sphincterotome was initially used for biliary cannulation in all patients. Cannulation was accepted as difficult in the case of failure of standard cannulation within 5 minutes or despite 5 attempts or insertion of the guidewire to the pancreatic duct 5 times. Three modalities in patients with difficult biliary cannulation were employed according to the structure and configuration of the papillae in addition to unintentional pancreatic cannulation: (1) NKF, (2) CPS, (3) Double guidewire technique or guidewire orientation/precut following pancreatic stenting. Latter was excluded to enable direct comparison between NKF and CPS groups. A total of 644 patients were recruited. Analyses were performed with 541 patients after the exclusion of 103 patients. Mean (SD) age was 60.4 (18.2) years, and 257 (47.5%) patients were male. While standard cannulation was successful in 366 (67.6%), difficult biliary cannulation was observed in 175 (32.4%) patients. NKF was performed in 101 (57.7%) patients, and cannulation success was 100% in the first ERCP session. In contrast, CPS was performed in 74 (42.3%) patients with a lower cannulation success rate (79.7%) than NKF ( P <0.001). Post-ERCP pancreatitis rate was higher in CPS (9.5%) than NKF group (3.0%, P =0.063). Bleeding and cholangitis were similar in both groups. In patients with difficult biliary cannulation with appropriate papillary structure and configuration, NKF should be used as the first choice in experienced hands because of high biliary cannulation success and low Post-ERCP pancreatitis risk.

Double guide-wire technique versus transpancreatic biliary sphincterotomy for difficult biliary cannulation: Real life experience from a referral center.

During ERCP for biliary indication, when a difficult bile duct (BD) cannulation occurs, with unintended access to the main pancreatic duct (PD), both double guidewire technique (DGW) and transpancreatic biliary sphincterotomy (TPBS) can be performed. We aimed to compare the technical success and adverse events (AEs) rate of these techniques. A retrospective analysis of patients with naïve papillae referred to the Pancreas Institute of Verona from January 2016 and July 2021 to undergo ERCP for biliary indications was performed. Overall, 202 patients (53.5% males, mean age 67.2 years) were evaluated (96 DGW, 106 TPBS). Malignant biliary stricture was the most common ERCP indication (78.2%). The rate of success in deep biliary cannulation was significantly higher in the DGW group (94.8%) compared to TPBS (79.2%) at the first attempt (p=0.001). This result was also confirmed in the subgroup of patients with malignant distal stricture (72/77, 93.5% vs 63/80, 78.8%, p=0.01). No significant difference in AEs rate, particularly in PEP incidence was found between the two groups. DGW demonstrated a higher success rate and similar safety profile compared with TPBS in difficult biliary cannulation. Based on this retrospective study, DGW should be preferred over TPBS in case of unintended PD cannulation. Further prospective studies are needed to confirm our results.

“Salvage techniques” are the key to overcome difficult biliary cannulation in endoscopic retrograde cholangiopancreatography

Although the efficacy and safety of salvage techniques for biliary cannulation in endoscopic retrograde cholangiopancreatography (ERCP) have been reported, few reports analyzed the choice of techniques and their clinical outcomes in large cohorts. This study aimed to evaluate the outcomes of biliary cannulation in patients with native papillae. We retrospectively identified 1021 patients who underwent initial ERCP from January 2013 to March 2020. We investigated background factors, treatment details, cannulation success rates, and adverse event rates. Then we analyzed a series of treatment processes, including salvage techniques such as double guidewire technique (DGT), needle knife pre-cutting (NKP), and transpancreatic pre-cut papillotomy (TPPP). The initial ERCP success rate using standard technique alone was 62.8%, which increased to 94.3% including salvage techniques. Salvage techniques were frequently required in patients with long oral protrusions (OR 2.38; 95% CI 1.80–3.15; p < 0.001). A total of 503 cases (49.3%) had long oral protrusions, 47.5% of which required the salvage techniques, much higher than 27.5% of not-long cases. Patients with long oral protrusions had a higher frequency of NKP. In conclusion, patients with long oral protrusions frequently required salvage techniques. Salvage techniques may help to overcome many difficult biliary cannulation cases.

Double guidewire technique stabilization procedure for endoscopic ultrasound-guided hepaticogastrostomy involving modifying the guidewire angle at the insertion site.

Endoscopic ultrasonography-guided hepaticogastrostomy (EUS-HGS) is often performed using a single guidewire (SGW), but the efficacy of the double guidewire (DGW) technique during endoscopic ultrasonography-guided biliary drainage has been reported. We evaluated the efficacy of the DGW technique for EUS-HGS, focusing on the guidewire angle at the insertion site. This retrospective cohort study included consecutive patients who underwent EUS-HGS between April 2012 and March 2021. We measured the guidewire angle at the insertion site using still fluoroscopic imaging. We compared the clinical outcomes of EUS-HGS with the DGW and SGW techniques. The factors associated with successful cannula insertion, need for additional fistula dilation and adverse event rate were assessed by a logistic regression multivariable analysis. The DGW group showed higher technical (p = 0.020) and clinical success rates (p = 0.016) than the SGW group, which showed more adverse events (p = 0.017) than the DGW group. Successful cannula insertion was associated with a guidewire angle > 137° and an uneven double-lumen cannula. The DGW technique made the guidewire angle obtuse at the insertion site (p < 0.0001). A guidewire angle ≤ 137° (OR, 35.6; 95% CI, 1.70-744; p = 0.0045) and intrahepatic bile duct diameter of the puncture site ≤3.0mm (OR, 14.4; 95% CI, 1.37-152; p = 0.0056) were risk factors for needing additional fistula dilation in a multivariate analysis, and additional dilation was a significant predictive factor for adverse events (OR, 8.3; 95% CI, 0.9-77; p = 0.026). The DGW technique can modify the guidewire angle at the insertion site and facilitate stent deployment with few adverse events.

Double guidewire technique (DGT): Optimising endovascular revision of juxta-anastomotic stenosis in AV-fistulae: A retrospective analysis.

Arteriovenous fistula (AVF) is the preferred angioaccess for haemodialysis but suffers from a high stenosis rate, juxta-anastomotic stenosis (JAS) being the most frequent. Percutaneous transluminal angioplasty (PTA) of JAS would have some advantage (such as mini-invasive and vein sparing treatment), but higher recurrence rate is observed as compared to surgery. We report results of juxta anastomotic stenosis PTA using the 'double guide technique' (DGT) as described by Turmel-Rodrigues, in a selected cohort from our Vascular Access Centre. From January to June 2018, 25 consecutive patients were treated by DGT. By means of retrograde access through the outflow vein by a 6 F introducer, two guide wires were navigated: one into proximal radial artery (GW1), the other into distal artery (GW2). GW2 was used to dilate juxta-anastomotic vein and anastomotic area with 6 mm high-pressure balloon, while by GW1 juxta-anastomotic artery was dilated with 4 mm semi-compliant balloon. Mean diameter of balloons were 6.7 and 4.1 mm for venous and arterial tract dilatation. Follow up was carried out up to 12 months. Prospectively collected data were analysed retrospectively. One-year primary and secondary patency was 52% and 95% respectively. Recurrence rate was 0.56 procedure/pt/year. Mean access blood flow at 12 months was 830 ml/min. Double Guidewire Technique is an effective and minimally invasive procedure. By avoiding under dilation of JAS the recurrence rate resulted quite satisfactorily in our population.

Safety and efficacy of different techniques in difficult biliary cannulation at endoscopic retrograde cholangiopancreatography

ABSTRACT Background Adverse events (AEs) are commonly seen at endoscopic retrograde cholangiopancreatography (ERCP) during difficult biliary cannulation (DBC). Therefore, attaining the right technique is essential to have improved outcomes. Methods Patients who had DBC over a 3-year period were assessed for outcomes. The protocol included double guidewire (DGW) technique, wire-guided cannulation (WGC) after pancreatic stent, precut sphincterotomy/fistulotomy, and EUS-guided rendezvous (RV). The success of various techniques and AE was studied. Results As per available case analysis, a total of 3680 patient details were assessed out of which DBC was noted in 471 (12.8%) patients with a mean (SD) age of 51.5 (17.4) years; majority being 330 (70.1%) males. Most patients underwent precut sphincterotomy 230 (48.8%); however, it was not successful in the first attempt in 10 (2.1%) patients with the success rate of 220 (95.6%). The success rate of DGW cannulation was 120 (95.2%), WGC after pancreatic stent was 64 (94.1%), EUS-RV was 34 (97.1%), and wire-guided repeat ERCP after 48 h was 10 (98.3%). AEs were noted in 52 (11.1%) patients. After precut, 32 (13.9%) patients developed AE out of which post-ERCP pancreatitis was noted in 20 (8.7%). Twenty-three patients had failed biliary access after all methods and 20 (86.9%) of those received successful percutaneous transhepatic biliary drainage. Conclusion Repeat ERCP after 48 h and EUS-RV appear prudent for DBC. Precut remains one of the preferred choices for most endoscopists when there is no entrance to PD. Further utilizing an algorithmic approach can contribute to higher success rates without compromising safety.

Transpancreatic precut papillotomy versus double-guidewire technique in difficult biliary cannulation: a systematic review and meta-analysis.

Background and study aims Approximately 11 % of biliary cannulations are considered difficult. The double guidewire (DGW-T) and transpancreatic sphincterotomy (TPS) are two useful techniques when difficult cannulation exists and the main pancreatic duct is unintentionally accessed. We carried out a systematic review and meta-analysis to evaluate the effectiveness and security of both DGW-T and TPS techniques in difficult biliary cannulation. Methods We conducted a systematic review in different databases, such as PubMed, OVID, Medline, and Cochrane Databases. Were included all RCT which showed a comparison between TPS and DGW in difficult biliary cannulation. Endpoints computed were successful cannulation rate, median cannulation time, and adverse events rate. Results Four studies were selected (4 RCTs). These studies included 260 patients. The mean age was 64.79 ± 12.99 years. Of the patients, 53.6 % were men and 46.4 % were women. The rate of successful cannulation was 93.3 % in the TPS group and 79.4 % in the DGW-T group ( P = 0.420). The rate of post-endoscopic retrograde cholangiopancreatography pancreatitis (PEP) was lower in patients who had undergone TPS than DGW-T (TPS: 8.9 % vs DGW-T: 22.2 %, P = 0.02). The mean cannulation time was 14.7 ± 9.4 min in the TPS group and 15.1 ± 7.4 min with DGW-T ( P = 0.349). Conclusions TPS and DGW are two useful techniques in patients with difficult cannulation. They both have a high rate of successful cannulation; however, the PEP was higher with DGW-T than with TPS.

Author commentary on Leena Kylänpää et al.

Leena Kylänpää et al. Transpancreatic biliary sphincterotomy versus double guidewire in difficult biliary cannulation: a randomized controlled trial

Evaluation of post-ERCP pancreatitis after biliary stenting with self-expandable metal stents vs. plastic stents in benign and malignant obstructions.

Background and study aims There are conflicting data regarding the risk of post-ERCP pancreatitis (PEP) with self-expandable metallic stents (SEMS) compared to polyethylene stents (PS) in malignant biliary obstructions and limited data related to benign obstructions. Patients and methods A retrospective cohort study was performed of 1136 patients who underwent ERCP for biliary obstruction and received SEMS or PS at a tertiary-care medical center between January 2011 and October 2016. We evaluated the association between stent type (SEMS vs PS) and PEP in malignant and benign biliary obstructions. Results Among the 1136 patients included in our study, 399 had SEMS placed and 737 had PS placed. Patients with PS were more likely to have pancreatic duct cannulation, pancreatic duct stent placement, double guidewire technique, sphincterotomy and sphincteroplasty as compared to the SEMS group. On multivariate analysis, PEP rates were higher in the SEMS group (8.0 %) versus the PS group (4.8 %) (OR 2.27 [CI, 1.22, 4.24]) for all obstructions. For malignant obstructions, PEP rates were 7.8 % and 6.6 % for SEMS and plastic stents, respectively (OR 1.54 [CI, 0.72, 3.30]). For benign obstructions the PEP rate was higher in the SEMS group (8.8 %) compared to the PS group (4.2 %) (OR 3.67 [CI, 1.50, 8.97]). No significant differences between PEP severity were identified based on stent type when stratified based on benign and malignant. Conclusions PEP rates were higher when SEMS were used for benign obstruction as compared to PS. For malignant obstruction, no difference was identified in PEP rates with use of SEMS vs PS.

Double Guidewire Technique Using an Uneven Double Lumen Catheter for Endoscopic Ultrasound-Guided Interventions.

Endoscopic ultrasonography (EUS)-guided interventions are often performed using a single guidewire (SGW), but there are a few reports on the use of double guidewire (DGW) technique to facilitate multiple drainage placement during EUS-guided drainage of pancreatic fluid collections. This DGW technique may have advantages other than multiple drainage placement during EUS-guided interventions such as scope stabilization, support for stone extraction and device insertion. Consecutive patients who underwent EUS-guided interventions between Feb 2012 and Apr 2019 were retrospectively reviewed. The rate and reasons of DGW technique, and clinical outcomes were evaluated. DGW technique was performed, using an uneven double lumen cannula (UDLC), which facilitates insertion of 0.025-in. and 0.035-in. guidewires. A total of 249 EUS-guided interventions were analyzed, and DGW technique was utilized primarily in 65 cases (25.7%) and as a salvage after failed SGW technique in 18 cases (7.1%). The reasons for DGW technique were 60 multiple drainage placement, 10 scope stabilization, 7 device insertion, 5 safety guidewire, and 4 antegrade stone removal. Insertion of UDLC and DGW was successful in 100%. Technical success rate of preplanned interventions was 92.7% (96.9% in primary DGW and 77.8% in salvage DGW technique). Adverse events were observed in 19.5% after DGW but were not related to DGW technique. DGW technique using UDLC during EUS-guided interventions was technically feasible and safe. In addition to multiple drainage insertion, it can potentially support complex EUS-guided interventions.

Su1213 DOUBLE GUIDEWIRE TECHNIQUE USING A DOUBLE LUMEN CANNULA FOR INTERVENTIONAL EUS

There are a few reports on the use of double guidewire (DGW) technique to facilitate multiple drainage placement for EUS-guided drainage of pancreatic fluid collections (PFC). However, this technique can provide advantages other than multiple drainage placement during interventional EUS, such as scope stabilization, support for stone extraction or device insertion.

Double Guidewire Technique versus Transpancreatic Sphincterotomy for Difficult Biliary Cannulation

Double Guidewire Technique versus Transpancreatic Sphincterotomy for Difficult Biliary Cannulation