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4. Direct Cholangioscopy
Direct cholangioscopy involves the insertion of a standard upper endoscope into the bile duct. Despite being reported in 1977 by Urakami [1], the technique did not become popular owing to the technical difficulties associated with direct biliary intubation with a forward-viewing endoscope. There has been recent interest in this technique owing to the popularity of single operator cholangioscopy. Direct cholangioscopy using conventional upper endoscopes offer significantly improved image quality compared to the SOC platform with possibilities of using image enhancement modalities such as the Olympus® narrow band imaging (NBI) or post processing systems such as the Fujinon® Flexible spectral imaging colour enhancement (FICE) and the Pentax® i-scan. Bigger suction and accessory channels with upper endoscopes are an additional and significant advantage over single operator cholangioscopy.
Equipment and Technique
The Olympus® (GIF-XP160, GIF-XP160N and GIF-XP260N) NBI-incorporated slim upper endoscopes with outer diameters of 5.5–5.9 mm and a working channel of 2 mm are used for direct cholangioscopy. Other platforms include the Fujinon® EG-530NW/530N2 FICE enhanced slim scope (also used as a trans-nasal endoscope) with a tip diameter of 5.9 mm and a working channel of 2 mm and the Pentax® EG-1690 K i-scan enhanced ultra-slim gastroscope with a tip diameter of 5.3 mm and a working channel of 2 mm.
Freehand cannulation of the bile duct with a slim gastroscope is technically challenging and is associated with a high failure rate [2]. Other techniques include overtube-assisted direct cholangioscopy and the anchoring-balloon method. Overtube assisted direct cholangioscopy [3, 4] involves the insertion of an overtube into the gastric-antrum/duodenum to prevent looping of the upper endoscope in the stomach. The endoscope is then manoeuvred into the bile duct by twisting and rotational movements. A generous sphincterotomy and/or sphincteroplasty is important in facilitating endoscope access into the bile duct. Advancement of the endoscope into the proximal bile duct is performed by further rotational and pullback movements. Access into the bile duct is not reliable and maintaining stability and advancing the endoscope into the proximal bile duct can be challenging. Another method of accessing the bile duct using a slim gastroscope involves inserting a duodenoscope first and performing a conventional ERCP in order to insert an 0.025–0.035-in. guidewire into the bile duct. The guidewire is positioned across the hilum and sphincterotomy, followed by balloon sphincteroplasty to 12–15 mm is performed to enable access. The duodenoscope is withdrawn over the wire and the slim gastroscope is advanced over the guidewire to the papilla. An extraction balloon is inserted through the gastroscope into the bile duct over the guidewire and the balloon is inflated proximal to the hilum. Using traction provided by the balloon on the hilum, the slim gastroscope is inserted into the bile duct. This method provides slightly better gastroscope stability compared to the overtube-assisted method. Endoscope insertion and movement involves rotational/torque and push-pull movements.
Applications include high definition biliary imaging, tissue acquisition, intraductal lithotripsy and intraductal polypectomy [5].
Technical success has been reported to be the highest (96%) with the anchoring balloon method, with technical success rates of 93% with the balloon overtube method and 72% with a combination of freehand cannulation and guidewire/anchoring balloon methods [3, 4, 6–11]. Complications include cholangitis (up to 10%) related to duct instrumentation and irrigation [12, 13], haemobilia and bile leaks associated with intraductal lithotripsy [14, 15]. The use of anchoring balloons has been demonstrated to be a risk factor for bile duct perforation in animal models [16]. There has been concern about the risk of air embolism following a case report of a patient developing left hemiparesis following direct cholangioscopy using the anchoring balloon technique [17]. Recent guidance [18] suggests using carbon dioxide (CO2) instead of air. However, two fatal cases of CO2 embolism during direct cholangioscopy [19] have highlighted safety issues with direct cholangioscopy using gas (air or CO2) insufflation.
Developments/Future Applications
Ongoing developments to the single operator cholangioscopy platform include better image definition, bigger accessory channels to facilitate greater tissue acquisition and therapy and the potential to incorporate advanced mucosal imaging capabilities. Biliary and pancreatic endotherapy, with the possibility of resecting small lesions, delivering haemostatic therapy, mapping of lesions to assist with surgery, surveillance of strictures/biliary or pancreatic lesions and facilitating targeted oncological therapy are the possible future applications of single operator cholangioscopy. Its ease of use has clearly revolutionized the field of hepatobiliary endoscopy and ongoing developments represent a paradigm shift in the management of hepatobiliary and pancreatic disease.
