Single-operator Digital Cholangioscopy for the Diagnosis of Malignant and Benign Biliary Strictures

Differentiation between malignant and benign biliary strictures can be challenging. Accurate differentiation of malignant biliary strictures from benign ones is crucial to guide management decisions. While a mass lesion involving the bile duct may be observed on imaging such as ultrasound (USG), computed tomography (CT), or magnetic resonance imaging (MRI) in patient presenting with obstructive jaundice, early malignancy of the bile duct may often present with a ductal stricture without an obvious mass on imaging. Diagnosis of early stage malignancy of the bile duct is desirable since the lesion may be amenable to surgical resection of curative intent.

Endoscopic retrograde cholangiopancreatography (ERCP) is an important diagnostic and therapeutic endoscopic technique in patients with obstructive jaundice and a suspected biliary stricture. While conventional tissue acquisition techniques such as brush cytology or intraductal biopsy of the biliary stricture is often performed during ERCP for tissue diagnosis, their sensitivities are suboptimal. The average sensitivities for brush cytology and intraductal biopsy were reported to be \~ 59% and \~ 63% respectively.

When the cause of a biliary stricture remains unclear despite conventional ERCP techniques for diagnosis, cholangioscopy is often performed during ERCP to clarify the diagnosis. Cholangioscopy performed during ERCP involves passing a small scope (\~ 10 French in size) through the working channel of the ERCP duodenoscope for direct visualization of the bile duct mucosa. This allows an endoscopist to obtain a visual impression (VI) and to perform targeted biopsy under direct visualization of the biliary stricture. The VI of a malignant biliary stricture is often characterized by the presence of intraductal abnormal tissue growth, and dilated, irregular, tortuous tumor vessels. During standard ERCP, cholangioscopy can be performed using a 2-operator "mother-baby" system, or a single-operator system. While the 2-operator "mother-baby" cholangioscopy technique can provide good image quality of the biliary stricture during ERCP, its use has been limited due to the cumbersome nature of the procedure requiring 2 endoscopists and the relative fragility of the video cholangioscope. Single-operator cholangioscopy (SOC) system, such as the SpyGlass Direct Visualization System, on the other hand allows a single operator to perform cholangioscopy during ERCP. In a recent meta-analysis of the studies using the optical fiber based SOC in the evaluation of indeterminate biliary strictures, the combined sensitivity and specificity of VI were 90% and 87% respectively, and the combined sensitivity and specificity of cholangioscopy directed biopsy were 69% and 98% respectively. The overall incidence of procedure-related adverse event (eg, infection, perforation, pancreatitis, etc) was reported to be 7.5% for diagnostic SOC during ERCP.

Despite the promising results of VI using the optical fiber based SOC from prior studies, the actual image quality in daily clinical practice is frequently regarded as fair only due to the use of a small optical fiber for imaging, and gradual loss of resolution over time from optical fiber damage. A SOC with better image quality is needed for better endoscopic diagnosis of a biliary stricture.

Recently, a digital SOC system (SpyGlass Digital System (SpyGlass DS), Boston Scientific, USA) has become available and has the potential to further improve the diagnosis of malignant and benign biliary strictures. The utility of this digital SOC in the evaluation of biliary strictures has not been well studied. We propose this study to evaluate the utility of the digital SOC during ERCP in the diagnosis of malignant and benign biliary strictures.