The “Demling-Classen” probe allowed for success sphincterotomy and the ability to inject contrast dye while the catheter was held in place. Meanwhile, Kawai developed a technique similar to modern-day needle knife sphincterotomy. These early breakthroughs were inspired by many sources, including the already ubiquitous use of baskets, stents, catheters and guidewires in the fields of cardiology, urology, and interventional radiology, and have undoubtedly laid the foundation for modern day ERCP. The evolution of ERCP has similarly been influenced heavily by radiologic advances such as magnetic resonance cholangiopancreatopgraphy, surgical advances such as laproscopic cholecystectomy, and endoscopic ultrasound . Today, the indications for ERCP are numerous, including but not limited to: biliary obstruction in the setting of stones, malignancy, infection, and parasites, types 1 and 2 sphincter of Oddi dysfunction, palliative and therapeutic ductal stenting, therapies for biliary tract malignancies , and many more. Regardless of the indication, ERCP has been and remains an invasive procedure that requires advanced training and finesse to safely achieve success.Since the advent of ERCP, selective biliary cannulation has remained not only the first and rate-limiting step of the procedure, vertical plant tower but also one of the most technically challenging portions. The incidence of complications while trying to achieve SBC ranges from 4%-30% depending on various research studies .

Failed biliary cannulation occurs in up to 20% of cases and itself is associated with a higher risk of complications including post-ERCP pancreatitis , bleeding, delayed therapy, and others. The standard endoscopic approach to uncomplicated SBC can be conceptualized chronologically as presented below.Successful ERCP hinges on proper scope placement and adequate visualization of the papilla. Most commonly, a side-viewing duodenoscope with a channel of 3.7-4.2 mm is used. Good visualization of the major duodenal papilla for biliary cannulation is achieved by placing the duodenoscope below the papilla . Shifting the patient into a left lateral decubitus or supine position can help improve the orientation of the scope and prevent it from falling back into the stomach. If a long scope position is required, the scope tip should be placed below the level of the papilla while applying gentle torque, thus allowing for appropriate infrapapillary orientation while maintaining visualization. This view can facilitate better visualization of the major duodenal papilla and a more stable scope position in patients with a very proximal papilla, among other potential indications . Note, this differs greatly from attempting main pancreatic duct cannulation, in which the duodenoscope tip is usually positioned perpendicular to the duodenal wall. Importantly, when pursuing ERCP limit insufflation as overdistention of the gastric tract can make duodenal visualization more difficult.

Occasionally, passing the duodenoscope into the stomach and aspirating gas, can prevent this. Once in position, with a steady hold on the duodenoscopy, the endoscopist is ready to choose a preferential technique for initial attempt of biliary cannulation. Standard methods of biliary cannulation include contrast-assisted cannulation and guide-wire assisted cannulation. In these methods, the majority of endoscopists use a sphincterotome since it can be adjusted into the direction of the biliary duct by pulling or relaxing the cutting wire and allows for sphincterotomy if necessary. The ST is inserted past the papilla, into the bile duct, with focus on minimizing papilla trauma and MPD cannulation or opacification. PD opacification is directly related to increased risk of PEP. Cannulation technique varies by hospital, physician comfort and available devices, we will review herein the most widely used techniques, in particular contrast vs wire guided cannulation. Contrast cannulation was first demonstrated with the Deming-Classen probe but is associated with a higher rate of PEP as compared with wire-guided cannulation , a technique first described by Bassi et al in 1987. In contrast-assisted cannulation, the tip of the ST or other cannula is inserted into the papillary orifice followed by injection of contrast under fluoroscopy to visualize the ampulla and distal common bile duct and subsequent advancement of the catheter into the bile duct. This technique often requires repetitive probing and multiple attempts of injecting contrast; factors that contribute to its association with high rates of PEP.

In WGC, a soft, hydrophilic guide wire serves as a tract that achieves desired duct selection without injection of contrast. The most common guide wire used is a 0.035 inch diameter hydrophilic tip guidewire. Hydrophilic tip guide wires are commonly used because of their reduced friction and ease of pushing. Guide wires with angled tips have been shown to lead to shorter cannulation times, likely because the angled tips are better able to follow the “S” shape of the intraduodenal segment of the bile duct and/or turn cephalad into the biliary system . Once an endoscopist has decided on WGC, the next step is deciding between the touch technique and the no-touch technique. In the former, the catheter is inserted into papillary orifice and then a guide wire is advanced under fluoroscopic guidance into the common bile duct . In the latter, the guide wire is advanced just beyond the tip of the catheter, and then the catheter with guide wire tip protruding is advanced directly into the papillary orifice under fluoroscopy and onward into the bile duct. Variations of WGC and the touch vs no-touch technique are commonly seen. The most common variations include: initial bile duct access with ST, followed by wire advancement vs ST advancement to the level of the papilla, after which the wire is used to achieve SBC or initial wire advancement past the tip of the ST, followed by “wire ST complex” advancement into the papilla . These techniques are used respectively: in papilla of normal size, position and SBC challenge vs with floppy or mobile papilla vs in scenarios where the papilla is small . Besides these techniques, the endoscopist can also decide between assistant-controlled wire-guided, using the wire to access the duct, the endoscopist to control the ST and the assistant to control the wire vs physician-controlled wire-guided cannulation, in which, the physician controls both the ST and the wire. During particularly challenging ERCPs with variant patient anatomy, contrast can opacify the intraduodenal portion of the CBD to better determine the direction of catheter advancement. Every time the ST comes in contact with the ampulla, contrast is injected, therefore, every cannulation attempt is also associated with risk of injecting contrast into the MPD and risk of PEP. Therefore, despite its procedural flexibility, WGC still carries a risk of PEP, intramural dissection, perforation of MPD side branches and creation of false passages .Even in the hands of experienced endoscopists, SBC can fail in up to 20% of cases . Multiple attempts at SBC increases the time patients spend on anesthesia, increase the risk of PEP, and delay therapeutic options. When difficult SBC is encountered, the endoscopist must decide to either persist with standard cannulation techniques, switch to more advanced techniques such as pancreatic guidewire or precut techniques, or abort the procedure. The safety of the patient, urgency of the procedure, time spent on cannulation, and cost of the tools are all important factors in this decision. Studies have shown that increased time spent on cannulation and a greater number of attempts can leads to increased rates of PEP and using advanced instruments such as various needle knife tools and additional guidewires can incur greater cost to both the patient and endoscopist. PEP is the most common and serious complication of ERCP. Defined as the development of pancreatitis post-ERCP, that requires unplanned hospital admission for at least 1 d and is a significant source of cost of care in ERCP. A systematic review of 21 prospective studies that included 16885 patients undergoing ERCP found that the overall rate of PEP was 3.5% and a mortality rate of 0.8%. Risk factors for PEP include suspected sphincter of Oddi dysfunction, female gender, growing strawberries vertically a previous history of pancreatitis . Difficult cannulation however is an independent risk factor for PEP . The risk of PEP was increased with precut sphincterotomy and pancreatic injection of contrast .

The risk is also increased in centers that perform low overall ERCP volume and low ERCP frequency per endoscopist , and is additive to other patient-related risk factors such as younger age or female sex. In the quest to improve cannulation rates, many techniques and tools were designed to not only facilitate biliary cannulation but also to reduce the risk of PEP.ERCP is an advanced technique that not all endoscopists perform routinely. Multiple studies have shown that technical success increases with experience, with competency in SBC usually achieve only after performing 350-400 ERCPs . Besides endoscopist practice and expertise, a multitude of additional factors can make biliary cannulation difficult, even for the practiced endoscopist. Correct duodenal positioning, and adequate visualization of the papilla are vital for success, however, size of the papilla,and variant patient anatomy can also affect the degree of difficult in cannulation. Although the hepatopancreatic ampulla usually enters the duodenum in the second portion, it is sometimes further distal in the third portion, making it more difficult to reach . The size of the papilla is another important factor . A small papilla can be difficult to identify, especially when there are excessive mucosal folds or other architectural distortions, and the tip of the ST may be larger than the papilla itself. A small papilla is also associated with initial contact of the ST with the septum instead of smooth insertion into the bile duct. If a wire lead cannulation technique is used, a small papilla makes it more difficult to redirect the ST without losing contact with the papilla. An extra-large papilla can also be problematic, as it can be more relaxed and unstable, making initial ST entry more troublesome. Also, the larger the papilla the more difficult further cannulation is, even with successful initial ST-papilla contact. Another common problem that arises is parallel tracts of the pancreatic and biliary ducts , this makes it difficult to identify if the guide wire has passed through the correct tract. In these circumstances it is sometimes beneficial to inject contrast to better visualize the anatomy . In normal anatomy, the papilla is on the inside of the mid-second portion of the duodenum; however, it is occasionally found more proximally or more distally . In these cases as well as others of altered papillary location or morphology, locating the frenulum of the longitudinal duodenal fold or the papillary “beard” can help localize the major papilla, and a catheter or ST can lift duodenal folds to permit better visualization. A periampullary diverticulum , alternatively termed juxtapapillary diverticulum, can also make SBC difficult . For example, PAD can obscure the papilla or distort its orientation. In cases of PAD, the biliary direction is not angulated superiorly, but instead runs horizontally, therefore there is no need to angulate the ST upward. If using an ST is unsuccessful, a standard catheter may be more beneficial for cannulation. Once PAD is suspected, it can be exposed by using the ERCP catheter to move the duodenal mucosa from the outer rim of the diverticular ring, exposing the papilla. Another method includes injecting the inferior section of the diverticulum to move the papillary tip into view. However, this technique is associated with higher risks of needle perforation, retroperitoneal leaks, and causing papillary edema with subsequent obscuration of the papillary orifice. Precut techniques and pancreatic duct stent placement are recommended to better expose the papilla for cannulation. When these methods are used, the rate of successful SBC in patients with PAD approaches those without. Once the papilla is identified, SBC is usually achieved easily. Notably, and as alluded to above, anatomic distortion from PAD can cause deviation in the location of the orifice of the CBD and MPD from their most common positions at 11 and 2 o’clock, respectively. When this occurs, simply clipping redundant or obscured folds can help with visualization . Patients with a Billroth II gastrectomy or Roux-en-Y surgery are considered to have complex post-surgical anatomy and SBC should be attempted at referral centers by endoscopists who have experience with such anatomy. Patient’s with these surgeries typically have the papilla in a portion of the duodenum retrograde from the gastrojejunotomy site. Because of this increased distance, push or balloon enteroscopy retrograde from the jejunum to the duodenum is frequently needed to reach the papilla.