Background and study aims: Chromoendoscopy using methylene blue is employed in the gastrointestinal tract to delineate neoplastic lesions. We tested the value of chromoendoscopy during choledochoscopy for characterization of local inflammation, neoplasias, and other alterations in patients with biliary strictures.
Methods: Patients with suspected biliary lesions were scheduled for endoscopic retrograde cholangiography with subsequent cholangioscopy. After initial inspection of the bile duct, 15 ml methylene blue (0.1 %) was administered via the working channel of the cholangioscope. Newly appearing circumscribed or unstained lesions were judged according to their macroscopic type and staining features. Methylene-blue-aided diagnosis was compared with either clinical follow-up of the patients or, in some cases, with the results of targeted biopsies.
Results: A total of 55 patients [biliary stenosis/cholestasis of unknown origin (n = 24), stenosis after orthotopic liver transplantation (n = 11), primary sclerosing cholangitis (n = 20)] were included. Methylene blue unmasked subtle mucosal changes and permitted macroscopic characterization of circumscribed lesions. Characteristic surface staining patterns were seen in chronic inflammation, dysplasia, and ischemic-type biliary lesions. Nondysplastic mucosa appeared homogeneously stained, whereas scarred strictures showed a weak uptake of methylene blue.
Conclusion: In this prospective feasibility study, methylene-blue-aided cholangioscopy was used for the first time to define different staining patterns of the bile duct. The differences in staining patterns identified normal, dysplastic, and inflamed mucosa of the bile duct, as was proved by follow-up or, in some cases, histology. Whereas homogeneous staining predicted the presence of normal mucosa, absence of staining of circumscribed lesions, or diffused staining of such lesions, represented neoplastic changes or inflammation.