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Cholangioscopy
Historically, cholangioscopy was performed with a fiberoptic mother (large-caliber duodenoscope) and daughter (cholangioscope) system requiring two endoscopists, two light sources, and two video monitors, if the endoscopy unit was fortunate enough to have two video cameras to interface with the respective endoscopes. The development of a video mother endoscope made the endoscopy suite a bit less cluttered, although even after video daughter endoscopes were markedly improved and variably marketed, equipment expense, fragility, and maintenance costs limited their use. It took the introduction of disposable daughter endoscopes, initially fiberoptic and currently digital, to change endoscopic retrograde cholangiopancreatography (ERCP) from a procedure in which virtually all diagnostic and therapeutic procedures were facilitated by fluoroscopy to one in which the endoscopist can look directly into the pancreaticobiliary tree both to improve diagnosis and to facilitate therapy. In recognition of this technological dichotomy, the authors have tried, Solomon-like, to split this chapter into two parts. We will leave it to the individuals performing cholangioscopy to decide whether they adopt one, both, or neither of these technologies and instead rely on interventional radiologists to provide access to the biliary tree through a transhepatic percutaneous biliary drain (PTBD) using the subsequent track as the cholangioscope entry port.
Single-Operator Cholangioscopy
Introduction
The advantages of single-operator cholangioscopy using the catheter-based fiberoptic SpyGlass system (FSOC; SpyGlass Direct Visualization System; Boston Scientific, Marlborough, MA) include the ability of a single endoscopist to perform cholangiopancreatoscopy and the use of a disposable 4-lumen 10-Fr catheter, reusable optical fiber, and four-way tip deflection (up–down and left–right) that is passed through the working channel (4.2 mm) of a standard therapeutic duodenoscope. The device is approved by the Food and Drug Administration (FDA) for both biliary and pancreatic applications. In February 2015, a fully disposable digital single-operator cholangioscope (DSOC) was introduced in the United States.
In an ex vivo study with FSOC, Chen compared four-quadrant access, simulated biopsy, irrigation flow rates, and optical resolution between FSOC and an endoscope-based system (CHF BP-30; Olympus Medical Systems, Tokyo, Japan). The author reported that the ability to access four quadrants for visualization and biopsy with FSOC was better than with the two-way tip deflection of the endoscope-based system (odds ratio 1.7 to 2.94, p < 0.001). A preliminary ex vivo study that included five investigators compared optical quality and maneuverability between DSOC and FSOC. A biliary tract model contained fixed and variable color targets. Runs (passes of the scope) were randomized, and DSOC outperformed FSOC by a higher percentage of visualized targets (96% vs 66%), successful targeting per run, and faster run times (all comparisons p < 0.01). Further, subjective parameters of image quality and ease of use were superior ( p < 0.001).
Equipment
FSOC has a control section that houses three ports: irrigation that feeds into two 0.6-mm channels, a 0.77-mm optical probe, and a 1.2-mm accessory channel that permits passage of guidewires, intraductal lithotripsy fibers, and miniature biopsy forceps. The control section is secured with a Silastic belt just below the working channel of the duodenoscope. The disposable 3.4-mm insertion tube has four steering wires embedded in its length. The 6000-pixel optical probe is a collection of light fibers that surround optical fiber bundles and is incorporated into a polyimide sheath, providing approximately a 70-degree field of view. The connector section entails a camera processor with 1/4-inch charge-coupled device (CCD) chip, a light source, an optical coupler that interfaces the optical probe with the light source and video camera head, a medical-grade isolation transformer, and a travel cart with a three-joint arm for extension. An irrigation pump with foot pedal and monitor are available through separate vendors. The DSOC has a complementary metal-oxide semiconductor (CMOS) chip for higher resolution, magnification, and field of view (120 degrees). It has a thin copper cable for digital transmission and lacks a separate fiber optic probe that may contribute to improved catheter tip articulation. A separate suction connection with the working channel seems to permit improved irrigation capability. The processor is portable for simplified setup.
Technique
For FSOC, the optical probe is preloaded into the access/therapeutic catheter and advanced to within a few millimeters of the catheter's bending portion to reduce the potential for damage during passage across the duodenoscope's elevator and ductal strictures. The DSOC system has the optical bundle incorporated into the catheter. Advancement through the duodenoscope's working channel is similar to the endoscope-based cholangioscope. Once the duct is entered with the access catheter, the optical probe is advanced gently beyond the catheter's tip for intraductal inspection. If resistance is encountered, the control section knobs should be unlocked and fluoroscopy may be used to determine whether the catheter's tip is straight. The endoscopist has control of the four-way steering dials and may periodically lock the dials to stabilize scope position at a target during tissue acquisition or intraductal lithotripsy. Irrigation is performed through two dedicated channels facilitated by a foot pedal. Irrigation rates should be kept as low as possible to reduce the risk of cholangitis.
Clinical Use and Efficacy
Intraductal Lithotripsy
Electrohydraulic lithotripsy (EHL) or laser lithotripsy (LL) can be used to treat both bile duct and pancreatic duct stones ( Fig. 27.1, A–E , and Fig. 27.2, A–E ). Cholangioscopic or pancreatoscopic visualization during intraductal lithotripsy helps to avoid duct injury. The 1.9-Fr nitinol EHL fiber contains two coaxially insulated electrodes ending at an open tip. Water or saline immersion is necessary and, as an advantage over endoscope-based cholangioscopes, the dedicated channels for irrigation provide a sufficient medium. During immersion, sparks are generated that produce high-amplitude hydraulic pressure waves for stone fragmentation. A generator produces a series of high-voltage electrical impulses at a frequency of 1 to 20 per second, with settings ranging from a power of 50 to 100. The tip of the EHL fiber should protrude no more than 2 to 3 mm from the scope and be positioned en face with the stone while the generator's foot pedal is depressed to deliver energy.
During LL, a laser beam is transmitted via a flexible quartz fiber through the working channel of the cholangiopancreatoscope. LL requires more precise localization of the stone, and though fragmentation is enhanced by direct contact, it can lead to a “drilling” effect. The application of repetitive pulses of laser energy to the stone leads to the formation of a gaseous collection of ions and free electrons of high kinetic energy. This plasma rapidly expands as it absorbs the laser energy and then collapses, inducing a spherical mechanical shockwave between the laser fiber and the stone, leading to stone fragmentation.
Clearance of Difficult Biliary Stone Clearance Using FSOC
A multicenter US experience using FSOC with LL included 69 patients, 89% of whom had extrahepatic or cystic duct stones and the remainder had intrahepatic stones. All patients had a minimum of one prior failed attempt at ERCP for stone extraction and required a mean of 1.2 LL sessions to achieve an impressive 97% complete clearance rate with a 4% adverse event rate. In a large, single-center FSOC series from India, holmium LL was used in 60 patients with previously failed attempts of mechanical lithotripsy (44%) or other factors such as Mirizzi's syndrome or stone impaction that precluded attempts at basket capture or large-balloon sphincter dilation. The mean stone size was 23 mm (range 15 to 40 mm) and 100% complete clearance was reported after a mean of 1.2 LL sessions. Interestingly, 24 potentially eligible patients were excluded because of portal hypertension or extensive stone burden occupying most of the bile duct and mostly referred to surgery without attempt at FSOC. In a small but significant series of 13 patients with cystic duct stones (four with Mirizzi's syndrome type 1), FSOC was used to achieve complete clearance of the cystic duct and bile duct in 10/13 (77%) patients during a total of 17 FSOC sessions.
In a multicenter international prospective registry study using FSOC, 66 of 297 total cases were for the treatment of difficult biliary stones and included EHL ( n = 50) and LL ( n = 16). The median stone size was 19 mm and the duration of index intraductal lithotripsy was 38 minutes. Ductal clearance was achieved in 100%: 47/66 (71%) at index study single-operator cholangioscopy (SOC) and the remaining 29% after an average of one to two ERCPs. Overall, in the appropriately identified patient, the treatment of difficult biliary stones remains an indispensable indication for single-operator cholangioscopy-guided intraductal lithotripsy.
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