Methylene blue-aided cholangioscopy in patients with biliary strictures: feasibility and outcome analysis. Reply to Maetani

We read Professor Maetani’s letter and comments about our study [1] with great interest. Maetani also reported their previous experience with methylene blue in the bile duct [2]. In their study protocol, the bile duct was analyzed by percutaneous cholangioscopy. Differences in methylene blue staining properties between cancerous and noncancerous epithelia were noted. Furthermore, endoscopic findings were compared with data on frozen sections of epithelia. Their investigation revealed that microscopic staining properties were not always significantly associated with endoscopic observations. Whereas 18 of 20 (90 %) specimens of normal epithelia revealed positive staining with methylene blue, 11 out of 16 (69 %) specimens of metaplastic epithelia were stained, with no staining obtained in cancerous epithelia. The cancerous epithelia stained significantly less often than either the normal or the metaplastic epithelia.

Although the Maetani study represents the first description of methylene blue use in percutaneous cholangioscopy, to our knowledge our findings provide the first report on the use of methylene blue in a large series of patients using peroral chromoscopy-guided choledochoscopy. In our present pilot study in 55 patients, we have shown that methylene blue-aided chromoendoscopy can be successfully performed in the bile duct during ongoing peroral cholangioscopy. Peroral chromoscopy-guided choledochoscopy made it possible to emphasize the imaging of certain features in the bile duct, such as mucosal structures, inflammation, and neoplastic lesions.

Our data suggest that such chromoscopy-guided cholangioscopy may be helpful in the identification and characterization of lesions in the bile duct, due to the generation of characteristic staining patterns [3]. So, neoplastic findings showed irregular mucosa with inhomogeneous and intensively dark blue staining patterns, whereas non-neoplastic findings had a smooth surface mucosa with homogeneous staining.

In the Maetani study, findings from tissues taken from the bile duct were compared with the endoscopic characteristics recognized during percutaneous transhepatic cholangioscopy. The results have proved that endoscopic findings are sometimes different from microscopic findings.

Maetani also reported that methylene blue was not only absorbed in the epithelium, but also attached to the mucosal surface or to mucus on the epithelium, thereby explaining some discrepancies between endoscopic and microstructural data. They suggested that methylene blue may adhere to mucus or exudate on the surface of the biliary epithelium. Under these circumstances, the mucus or exudate may disturb the contact of methylene blue with the superficial epithelia. We agree with them on this point, and it is well known that before application of methylene blue, the mucus on the mucosal surface must be removed by application of a saline to allow the uptake of dye into the epithelial cells. Removal of the superficial exudate helps to accurately evaluate the methylene blue staining. We removed excess dye by suction after a waiting period of 2 – 3 minutes. Then to optimize the view, a sterile saline solution was instilled continuously through the accessory channel of the cholangioscope in order to flush any mucus away. This approach reduces potential misinterpretation due to remaining mucus in the bile duct.

However, both studies come to the same conclusion that methylene blue-aided chromoendoscopic analysis of the bile duct can be easily achieved and results in characteristic staining patterns. Because it is well accepted that the bile duct presents a mucosal condition that is of great interest to gastroenterologists and surgeons because of the difficulties in differentiating between malignant and benign biliary lesions, our findings collectively emphasize that methylene blue-aided cholangioscopy highlights areas of interest during cholangioscopy and permits the macroscopic characterization of lesions.

Competing interests: None

References

• 1 Hoffman A, Kiesslich R, Bittinger F. et al . Methylene blue-aided cholangioscopy in patients with biliary strictures: feasibility and outcome analysis.  Endoscopy. 2008;  40 563-571
• 2 Maetani I, Ogawa S, Sato M. et al . Lack of methylene blue staining in superficial epithelia as a possible marker for superficial lateral spread of bile duct cancer.  Diagn Ther Endosc. 1996;  3 29-34
• 3 Hoffman A, Kiesslich R, Moench C. et al . Methylene blue-aided cholangioscopy unravels the endoscopic features of ischemic-type biliary lesions after liver transplantation.  Gastrointest Endosc. 2007;  66 1052-1058