1. Introduction and History of Cholangioscopy
Endoscopic Retrograde Cholangio Pancreatography (ERCP) is an important therapeutic procedure for the diagnosis and treatment of biliary and pancreatic diseases. Recent innovations in endoscopy have facilitated direct endoscopic visualization of the biliary tree by cholangioscopy .
Post-operative T-tube tract cholangioscopy
Percutaneous transhepatic cholangioscopy
The first three techniques have become outdated due to the advancement in per-oral cholangioscopic techniques and should be restricted to selected patients in whom per-oral cholangioscopy is not feasible.
Dual-operator technique (using a mother and daughter scope system)
Single operator cholangioscopy (SOC) involves the use of a catheter-based system that can be controlled by a single operator [2, 3]. SOC has gained widespread acceptance as the standard technique for intervention in the biliary system because of its ease of use and widespread availability.
Cholangioscopy using a mother–daughter system has been available since the 1980s and represented the gold standard for cholangioscopy [4, 5]. This system has a dedicated cholangioscope (‘daughter’) inserted through a duodenoscope (‘mother’) and requires two operators. The cholangioscope is generally a 2.6–3.4 mm endoscope with a working channel of 0.5–1.2 mm which permits the use of accessories [6, 7].
The drawback of the “mother-daughter” or dual-operator per-oral cholangioscopy is the requirement of two endoscopists, with one operating the cholangioscope, while the second endoscopist controls the duodenoscope. This system is cumbersome, labour intensive, and time consuming . Despite the benefits of the mother-baby system in providing a detailed assessment of the bile duct, the fragility of the system, with damage to the daughter scope common across the elevator of the duodenoscope and the prohibitive cost of repair/replacement has limited its uptake.
Innovations in the original single-operator cholangioscopy system with high-resolution digital technology using a complementary metal-oxide semiconductor (CMOS) chip resulted in improved image quality and improving manoeuvrability of the catheter tip. This new, digital single-operator cholangioscopy system (SpyGlass™ DS Direct Visualization System) has a 10.8 Fr access and delivery catheter with a 10.5 Fr tapered-tip designed for easier cannulation . This is a more advanced cholangioscopic system with higher image quality and is equipped with suction, which was not available with the legacy system.
Direct Cholangioscopy with Ultra-slim Endoscope
Ultra-slim upper endoscopes of 5.4–5.9 mm diameter were originally designed for use in paediatric patients and trans-nasal endoscopy. Ultra-slim endoscopes can be used to access the bile duct after a large sphincterotomy and/or sphincteroplasty. Owing to their larger diameter, these endoscopes can only be used in patients with a dilated bile duct. The ultra-slim endoscope can be navigated across the relatively acute angle of the biliary system from the second part of the duodenum over a guidewire or using a balloon to initially anchor the guidewire at the hilum [7, 12]. The duodenoscope, used to initially deploy a guidewire or balloon into the bile duct, is then completely removed and under fluoroscopic and endoscopic control, the ultra-slim endoscope is then advanced over the guidewire. Large loop formation, which hinders advancement into the biliary tree, is common during attempted insertion of a slim endoscope into the biliary system through the ampulla, particularly within the gastric fundus or the deep portion of the duodenum . Hence, this technique is not as popular as compared to single operator cholangioscopy. However, the advantages of direct cholangioscopy are superior endoscopic views and a larger accessory channel within the endoscope, which can accommodate larger biopsy forceps and other accessories such as argon plasma coagulation (APC) catheters.
The important anatomical landmarks while performing cholangioscopy are the ampulla of vater (major papilla), common bile duct, cystic duct and common bile duct confluence, common hepatic duct, hilum and intrahepatic ducts. Intrahepatic ducts can be divided further into right anterior, right posterior and left intrahepatic ducts.
Cholangioscopic appearance of the normal ductal mucosa has a creamy/pearly colour with a well-defined vascular pattern. Villous formation is also more noticeable in the distal bile duct, adjacent to the papilla.
The normal ampulla (also termed the major papilla) varies considerable in size, shape and appearance and is generally seen as a circular/valvular structure on the medical wall of the second part of the duodenum. The course of the bile duct may be obvious as a longitudinal bulge into the lumen for 1–2 cm above the major papilla. A horizontal duodenal muscular fold may sometimes hide the major papilla. The orifice of the bile duct is at the apex of the papillary structure. The major papilla may be patulous with several fleshy fronds of protruding mucosa or may be obscured by duodenal folds.
Common Bile Duct
The common hepatic duct continues inferiorly into the common bile duct, with the cystic duct commonly inserting into the common hepatic duct but occasionally into the common bile duct. Anatomically, the common bile duct generally courses anterior to the portal vein. The hepatic artery is usually located slightly laterally, with the duct, artery and vein comprising the portal triad.
Cystic Duct—Common Bile Duct Confluence
This is an important anatomical landmark for difficult bile duct stones requiring cholangioscopy-guided therapy. Stones situated at the cystic duct-common bile duct junction can be challenging to extract using conventional endoscopic techniques.