**3.3 Cholangioscopy**

In cases where the diagnosis of the biliary stricture remains unclear after conventional MDCT, MRI and EUS evaluation, directly visualization of the appearance of the ductal strictures and biopsy can be helpful in differentiating benign from malignant disorders (Figure 3). Although video "mother-baby" cholangioscope provides high quality images, it is fragile and often lack of accessory channel for tissue sampling (Nguyen, 2009; Nguyen et al., 2009). The diagnostic yield of malignancy based on cholangioscopic appearance of the intra-ductal lesion varied from 70% to 88% (Nguyen, 2009; Nguyen et al., 2009). Currently, tissue sampling is only possible with the single-operator disposable SpyGlass system, which has a 1.2mm accessory channel. Although SpyGlass guided tissue sample is successful in up to 96% of cases, its overall accuracy in confirming a malignant stricture is only modest (49% of cases) (Nguyen, 2009; Nguyen et al., 2009). This is mainly due to the poor sensitivity of SpyGlass guided biopsy in the diagnosis of malignancy from extrinsic cancers (8%) as compared to that of intrinsic cancers (66%) (Nguyen, 2009; Nguyen et al., 2009).
