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Cannulation of the Major Papilla
Despite advances in imaging and device technology over the past decade, endoscopic retrograde cholangiopancreatography (ERCP) continues to be technically challenging and subject to adverse events and procedure failure. To some extent this is accounted for by the knowledge that among the most difficult aspects of the procedure is the very first step: selective biliary cannulation (SBC). Outside of expert high-volume centers, failed biliary cannulation occurs in up to 20% of cases. Repeated and prolonged attempts at cannulation increase the risk of post-ERCP pancreatitis (PEP), delay definitive therapy, and necessitate alternative therapeutic techniques with inferior safety profiles. Recent data have also shed light on appropriate requirements for trainee competency in cannulation (see Chapter 9 ). As expected, trainee technical success increases with experience, and competency in biliary cannulation is usually reached only after performing 350 to 400 ERCPs, a threshold substantially higher than previous estimates.
In any patient with a given preprocedural risk profile (based on age, sex, and indication), cannulation technique and outcome is the primary determinant of adverse events in most ERCP procedures; it is obviously important in achieving success. Preceding this and not to be overlooked, the first step in optimizing outcomes and minimizing ERCP adverse events is appropriate patient selection. This is done by avoiding diagnostic ERCP and using other, less hazardous imaging modalities—such as endoscopic ultrasonography or magnetic resonance cholangiopancreatography (MRCP)—when the pretest probability of the need for intervention at ERCP is low. Careful patient selection eliminates the awkward situation that may occur when conventional cannulation techniques fail and the probability of pathology is low. Then it should be decided whether to proceed with a more aggressive and potentially more hazardous ancillary technique (e.g., precut) to achieve SBC. Suddenly the risks of continuing the procedure may dramatically outweigh the clinical benefit of technical success. Therefore all possible cannulation scenarios must be envisaged before ERCP is undertaken, and the endoscopist must be comfortable with an array of techniques. Once under way, the risk profile of the patient and the intent of the procedure must be continuously factored into the approach. In an elderly patient with jaundice caused by obstructive biliary disease and no other anatomic or patient-related risk factors, time can be spent on different conventional access techniques to achieve SBC. Conversely, in younger patients with difficult cannulation or possible sphincter of Oddi dysfunction, early and repeated access to the pancreatic duct (PD) will dictate a change in cannulation strategy and early placement of a pancreatic stent. However, sometimes the best decision during ERCP is to stop the procedure.
The philosophy underpinning successful ERCP practice is precise cannulation technique with resultant swift and efficient, preferably single or minimal pass, SBC.
Establishing the Duodenal Position
Upon reaching the top of the second part of the duodenum, two options for achieving an “en face” position are available to the endoscopist:
- 1.
The endoscope is gently advanced for 2 to 3 cm with slight counterclockwise torque, the left-right (LR) wheel is turned right, and then with clockwise torque of the shaft and gentle upward deflection of the big wheel, the instrument is withdrawn and the endoscopist has the sense of pulling oneself beneath the papilla. This is our preferred technique, and it minimizes endoscopic insertion length and patient discomfort. Caution should be taken in cases of stenotic or relatively fixed duodenal segments as it is possible to tear the duodenal wall during endoscope withdrawal, particularly if the LR wheel is locked.
- 2.
Alternatively, one may pass the tip beyond the papilla to the distal second part and again perform full right positioning of the LR wheel and essentially repeat the endoscope withdrawal steps outlined in 1.
For occasions with a mobile second part of the duodenum (e.g., after hepatic lobectomy) or more inferiorly located papilla, technique 2 may be the only means to achieve a satisfactory position. Initially the papilla should be positioned in the center of the monitor for inspection, but because the catheter will emerge from the lower half of the right edge of the screen image, for optimal cannulation the papilla's monitor position should generally be slightly more superior and to the right. If the video screen is divided into four equal quadrants, then generally the optimal position sees the papilla located in the left lower corner of the right upper quadrant ( Fig. 14.1 ).
For successful SBC, the duodenoscope position should be stable and the endoscopist must feel as though the scope tip is below or at least adjacent to the papilla (i.e., the papilla is easily positioned above the horizontal midpoint of the monitor). If the endoscope is above the papilla, cannulation will be difficult. Cannulation attempts should not commence until all efforts to achieve a satisfactory position have been exhausted. Occasionally a long scope position will be necessary. This is achieved by pushing the instrument inferiorly with counterclockwise torque on the shaft toward the left-hand wall (as seen on the monitor). The insertion tube of the scope will bow along the greater curve of the stomach, with the tip of the endoscope dipping below the papilla, and then in approximately 80% of cases come back up adjacent to the papilla but in a more favorable infrapapillary orientation.
Movement of the up-down (UD) or large wheel will move the endoscope tip toward and away from the papilla, respectively. Small movements of the LR wheel move the endoscope above and below the papilla, with larger movements of this wheel moving the scope from side to side. The size, morphology, and orientation of the papilla; its relationship to the adjacent duodenum; and the anticipated direction of the intrapapillary and suprapapillary bile duct inform the cannulation approach. The presence of a peripapillary diverticulum may modify the approach (see section “Peripapillary Diverticulum”). The most common reason why an initially satisfactory duodenal position deteriorates is overdistension of the upper digestive tract, usually gastric. Aspirating gas and minimizing insufflation may remedy this situation, but on occasion it may be necessary to withdraw the endoscope into the stomach, remove air, and repeat the duodenal insertion phase. It is important to avoid gas insufflation during pauses in the procedure when full luminal insufflation is not necessary.
Devices and Equipment for Cannulation (See Also Chapter 4 )
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Straight or angle-tipped hydrophilic guidewires: usually 0.035 inches, occasionally 0.025 or 0.021 inches; Jagwire or Dreamwire (Boston Scientific, Natick, MA), Tracer Metro and Acrobat wire (Cook Endoscopy, Winston-Salem, NC), or Visiglide wire (Olympus Corporation, Tokyo, Japan). When encountering difficult cannulation of the PD or for use through a 5-4-3 Fr cannula, a 0.018-inch platinum-tipped wire (Roadrunner; Cook Endoscopy) is useful. Many other varieties of specialty wires exist and may have particular advantages in niche situations.
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Triple-lumen sphincterotomes (STs) with 20-mm, 25-mm, or 30-mm cutting wire: CleverCut3V and CleverCut2V (Olympus Corporation); FusionOMNI with dometip, DASH ST, or Tri-Tome (Cook Endoscopy); or Autotome, Dreamtome, Hydratome, Jagtome, or TRUEtome RX (Boston Scientific, Natick, MA).
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Three-French or 5-Fr pancreatic stents: Zimmon or Geenen Sof-Flex (Cook Endoscopy), Advanix (Boston Scientific, Marlborough, MA), or Freeman-Aliperti (Hobbs Medical, Stafford Springs, CT).
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Microprocessor-controlled electrosurgical generator delivering alternating cycles of short pulse cutting with more prolonged coagulation current: ERBE VIO 300 (ERBE Elektromedizin GmbH, Tubingen, Germany) or Olympus ESG-100 (Olympus Corporation).
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Needle knives (Olympus Corporation, Cook Endoscopy, Boston Scientific).
Cannulation Technique
Most expert endoscopists opt to cannulate the naive papilla with an ST, given that almost all procedures are now therapeutic and, compared with a catheter, the ST orientation to the distal biliary tree is favorable and adjustable. High-quality comparative data are limited but indicate superior outcomes with an ST compared with a standard catheter. The imprecise technique of impacting the ST into the papilla and injecting contrast should be avoided. This results in papillary trauma and often leads to PD opacification. In general, the preferred technique is to selectively insert the ST beyond the papilla and into the bile duct atraumatically. To comprehend the mechanics of biliary cannulation, a useful analogy is to imagine passing your hand up a shirt sleeve that is hanging over the back of a chair. The sleeve may be of variable length and caliber, draped over the chair at varying angles, and either floppy or more rigid. It is not possible to fix the sleeve in place, and so gentle manipulation is required and forceful manipulation with distortion of the sphincter mechanism is unlikely to be successful.
Guidewire or Contrast?
Traditional cannulation techniques relied on initial contrast opacification of the biliary tree. However, the contrast cannulation (CC) approach may result in inadvertent filling of the PD and progressive stepwise opacification of the body or tail from repeated injections to determine whether the cannulating device is in the biliary tree. The risk of PEP increases with the number of PD injections and extent of PD opacification. In contrast, wire-guided cannulation (WGC) can enhance technical success while reducing the risk of PEP. A soft-tip hydrophilic guidewire may facilitate deep instrumentation of the bile duct, confirm duct selection without contrast injection, and in most cases totally avoid contrast opacification of the PD. In addition, gentle passage of the wire into the PD may not significantly increase the risk of PEP. A broad body of evidence now suggests that the wire-guided technique is the preferred approach.
A recent Cochrane systematic review and meta-analysis of 12 randomized controlled trials (RCTs) comprising 3450 patients assessed the effectiveness and safety of WGC and the conventional CC technique. The WGC technique, compared with CC, was associated with greater primary cannulation success (relative risk [RR] 1.07, 95% confidence interval [CI] 1.00 to 1.15), significantly reduced PEP (RR 0.51, 95% CI 0.32 to 0.82), less need for precut sphincterotomy (RR 0.75, 95% CI 0.60 to 0.95), and no increase in other ERCP-related adverse events. Ten studies comprising 1497 patients in the WGC technique and 1489 patients in the CC technique group were included in the main analysis for primary cannulation success rates. Significant heterogeneity among studies was noted ( p < 0.00001, I 2 = 83%). Unweighted pooled primary cannulation success rates were 83.6% for the WGC technique and 77.3% for the CC technique. The number needed to treat (NNT) was 18 (95% CI 9 to 625). In sensitivity analyses, the results remained statistically significant with both odds ratio (OR) (OR 1.50, 95% CI 1.05 to 2.14; p = 0.03) and a fixed-effect model (RR 1.08, 95% CI 1.04 to 1.12; p < 0.00001). Secondary cannulation success, defined by cannulation success after changing to the alternate technique, was reported in 4 of the 7 crossover studies comprising 100 patients in the WGC and 169 patients in the CC technique group. Unweighted pooled secondary cannulation rates were 34% after crossover to the CC technique and 49.7% after crossover to the WGC technique; however, there was no statistically significant difference in the cannulation success rates after crossover to either technique (RR 0.74, 95% CI 0.41 to 1.31; p = 0.30).
All 12 studies included in the main analysis reported PEP rates and included a total of 1784 patients in the WGC technique and 1666 in the CC technique group. Again, there was significant heterogeneity among the studies ( p = 0.04, I 2 = 45%). Unweighted pooled rates of PEP were 3.5% for the WGC technique and 6.7% for the CC technique. The WGC technique significantly reduced PEP compared with the CC technique based on ITT analysis (RR 0.51, 95% CI 0.32 to 0.82; p = 0.005) or per-protocol analysis (RR 0.51, 95% CI 0.32 to 0.83; p = 0.007). The NNT was 31 (95% CI 19 to 78). In sensitivity analyses, the results remained robust with either odds ratio or a fixed-effect model.
In all, the results indicate that the WGC technique significantly reduces PEP and enhances primary cannulation success. Although it is unlikely that in routine clinical practice biliary cannulation is performed with either technique in isolation, the results of the Cochrane review support use of the WGC technique as the most appropriate first-line primary cannulation technique.
Although the evidence is strong, some caveats are worth noting when interpreting the data. The significant heterogeneity among the included studies with respect to outcomes of cannulation success and PEP may be explained by differences in trial design, variability in blinding, use of prophylactic pancreatic stents, precut sphincterotomy, cannulation devices, operator experience, and involvement of trainees. Furthermore, the consensus definition of PEP developed in 1991 was not universally adopted, but it was used in most studies. Another potential limitation was the inclusion of five crossover studies, which may have diluted the effect of WGC for the prevention of PEP. Whether WGC is cost-effective relative to CC also remains to be proven. Nonetheless, a significant reduction in the risk of PEP with the WGC technique was found. The variability across the studies likely reflects real-world practices, and the narrow confidence intervals for the measured parameters suggest adequate precision of the results and therefore applicability to contemporary clinical practice.
At least three variations of the WGC technique exist, and their use does and should vary depending on the morphology of the papilla.
- 1.
Direct access with the ST: The ST is used to enter (drop or pop into) the biliary duct (BD) and then the wire is advanced, with its direction confirming SBC. This technique is used frequently by experienced biliary endoscopists and will swiftly succeed in more than 50% of cases. It is primarily used when the papilla is of normal size and position and a cannulation challenge is not anticipated. It may also work with a floppy papilla.
- 2.
ST then wire: The ST is advanced 2 to 3 mm beyond the luminal aspect of the papilla in the biliary orientation and then the wire is gently advanced (either by the assistant [long wire] or by the endoscopist or the assistant [short wire]) to achieve SBC. This is useful in a floppy or mobile papilla or when technique 1 fails; this modification can be swiftly applied without withdrawing the ST. The ST can be used to straighten the intramural segment by drawing back on the impaled papilla and applying suction to encourage the papilla down onto the bowed ST.
- 3.
Wire lead technique: The tip of the wire is positioned approximately 2 mm beyond the tip of the ST and the wire ST complex is then advanced in the biliary direction into the papilla. It may drop or pop into the BD as in technique 1, or the wire can be advanced as in technique 2 to achieve SBC. This technique is especially useful when the papilla is small and the tip of the ST is larger than the papilla. The wire acts as an introducer ( and ).
These techniques are all somewhat different, although they are unified by the goal of contrast-free SBC. Potentially they all have advantages and risks. For instance, a forcefully inserted guidewire may dissect intramurally within the papilla, creating a false passage. It is likely, although not yet proven, that a given technique may have advantages dependent on patient-related factors, particularly the morphology of the papilla. A large floppy papilla with a long intraduodenal segment of BD would be better suited to initial ST insertion beyond the orifice and then the intraduodenal segment straightened; SBC may subsequently occur with either wire or ST directly. Further trials of WGC more closely reporting on papillary morphology would be helpful.
Guidewire tip shape has also been postulated as a possible factor in cannulation success. Straight-tipped and angle-tipped guidewires have been used for WGC; however, there has been no clear evidence to suggest superiority of one type over the other. Other tip shapes such as J-tip and loop-tip wires have also been studied in small RCTs, again without obvious benefit with respect to the success of biliary cannulation. Comparison of wire caliber, in particular 0.025-inch with 0.035-inch wires, has not been shown to either significantly improve the success of biliary cannulation or reduce the incidence of PEP. As such, a conventional 0.035-inch soft-tipped straight hydrophilic guidewire may be reasonably used routinely for WGC, although in select anatomic situations one of the other wires may be useful.
Avoidance of PEP is a primary objective of every ERCP procedure; however, at times it is unavoidable even in expert hands. Of paramount importance is attention to basic ERCP technique and careful attempts at cannulation. Two additional factors, pharmacologic prophylaxis and pancreatic stenting, likely also have a role in reduction of PEP risk. Overall, the available data suggest that rectal administration of nonsteroidal antiinflammatory drugs (NSAIDs) can reduce the incidence of PEP. Six meta-analyses published between 2009 and 2014 compared rectal NSAIDs versus placebo for prevention of PEP in high-risk and unselected patients. All showed benefit of NSAIDs in reducing both the incidence and severity of pancreatitis, with NNT estimated to be between 11 and 17 to prevent one episode of pancreatitis. Whether rectal NSAIDs should be prescribed to all patients undergoing ERCP or reserved only for those at higher risk of PEP remains controversial. Two recent RCTs assessing outcomes from routine periprocedural administration of rectal indomethacin or placebo to consecutive average-risk patients found conflicting results with respect to prevention of PEP. Rectal NSAIDs have also been indirectly compared with pancreatic stenting. A meta-analysis comparing rectal NSAIDs with pancreatic stenting found that rectal NSAIDs were superior for the prevention of PEP (OR 0.48, 95% CI 0.26 to 0.87). Randomized controlled studies directly comparing rectal NSAIDs to pancreatic stenting, however, have not been completed, although at least one is currently under way. Prevention of PEP and other adverse events of ERCP are discussed further in Chapter 8 .
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