Abstract
The Role of SpyGlass in Biliary Tract Diseases
Dr Nonthalee Pausawasdi
Mahidol University
Endoscopic Retrograde Cholangiopancreatography (ERCP) is a standard method for the evaluation and treatment of biliary tract disorders. However, successful diagnosis of biliary strictures and management of large bile duct stones can be challenging despite refinement in techniques.
Peroral Cholangiopancreatoscopy (CP) is the examination of the bile ducts with the use of a fiberoptic cholangioscope for direct visualization of the biliary tree during an ERCP. The fiberoptic scope can be passed through a therapeutic duodenoscope directly into the biliary tract. An endoscopist may choose to perform a cholangioscopy in the event that x-ray imaging from an ERCP is insufficient to make an adequate diagnosis, or therapeutic intervention requiring direct visualization. CP-directed forceps biopsy can be of value in diagnosing bile duct lesions with relatively high sensitivity and specificity (1,2). Peroral CP has also been shown useful in therapeutic interventions in the treatment of complicated bile duct stones especially those in the intrahepatic ducts and large stones in the common bile duct (3-11). The efficacy of percutaneous choledochoscopy for difficult biliary stones has also been demonstrated in several large series. However, due to its more invasive nature, percutaneous techniques should be reserved for intrahepatic strictures or stones that are inaccessible by a retrograde transpapillary approach (12).
Although cholangioscopes have improved greatly in recent years, CP has not been commonly performed due to the fragility of the optical fibers and the approach has been labor intensive. Two endoscopists are required i.e. one to operate the duodenoscope and the other to steer the cholangioscope and operate its working channel. The Cholangioscopes have improved greatly in recent years nonetheless several technical difficulties remain. Among the other important limitations of the currently commercially available cholangioscopes are limited tip deflection and suboptimal irrigation capabilities (2,13,14).
The recently described SpyGlass Direct Visualization System is one of the latest advancements in intraductal visualization during a cholangioscopy. The SpyGlass System is designed to allow the physician the ability to directly visualize the site of interest whether it be a stricture, stones or an area of concern. This new direct visualization system also allows a single physician to potentially secure a definitive diagnosis and perform therapeutic intervention in one procedure. The SpyGlass System utilizes a miniature 6,000-pixel fiber-optic probe that attaches to a camera head. The probe is inserted through a single-use access and delivery catheter that can be steered in four directions to access and inspect the treatment area. The System attaches directly to a standard duodenoscope, eliminating the need for a second physician operator (15).
The SpyGlass Probe is introduced into the SpyScope Access and Delivery Catheter. The bile duct is cannulated, and the SpyScope Catheter guides the SpyGlass Probe into the biliary tree. The SpyScope Catheter and SpyGlass Probe are maneuvered up to the desired area of interest within the duct for direct visualization. Additionally, selected ducts and branches of interest can be examined during repeated advancement and withdrawal of the system utilizing the four-way tip deflection. Two separate channels in the SpyScope Catheter allow for adequate irrigation to clear debris and aid in guiding both optical and accessory devices for diagnostic and therapeutic applications during endoscopic procedures in the biliary system including the hepatic ducts. In a laboratory simulator ex vivo, the system significantly improved bile duct access and increased the biopsy success rate compared with a conventional choledochoscope. In a porcine model, the system also proved efficient in obtaining samples that were adequate for histologic examination (15). The technical feasibility of Spyglass procedures in patients with indications for CP was clearly demonstrated. The procedural success rate exceeded 90%. Biopsy specimens collected by forceps under SpyGlass guidance were adequate for histologic characterization in 95% of cases. All SpyGlass-directed EHL procedures were successful. This technique has also found to be safe in clinical feasibility study (16).
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