Reply to Peng & Chow

We appreciate the comments of Peng & Chow on our study “Direct peroral cholangioscopy using an ultraslim upper endoscope for management of residual stones after mechanical lithotripsy for retained common bile duct stones” [1]. There are many factors that contribute to the presence of residual bile duct stones after stone extraction [2]. Although the maximum size of residual stones in our study was 9 mm, we have performed various procedures to confirm and remove residual bile duct stones. Despite such efforts, residual stones still occur because risk factors for residual stones are various, so more improved methods for diagnosis and treatment are necessary.

Endoscopic sphincterotomy (EST) is expected to minimize residual stone formation after stone extraction, but it is not perfect. Itoi et al. detected residual stones 6 days, on average, after extraction or lithotripsy with EST [3], and we observed residual stones 15 days after endoscopic mechanical lithotripsy. These stones were not expelled even after EST and ultimately may cause recurrent stones. Intraductal ultrasonography (IDUS) can also be used to diagnose residual stones [4] [5], but it is limited by pneumobilia conditions from extraction procedures that make it difficult to obtain a proper echo image in the bile duct. Even after the detection of fragments, direct stone removal is impossible.

The application of direct peroral cholangioscopy (POC) for diagnosis and treatment of various biliary diseases has been validated in several studies [6] [7] [8] [9]. In the present study, we have described another application for direct POC in the diagnosis and treatment of residual stones after mechanical lithotripsy. We agree that direct POC may not be capable of reaching intrahepatic ducts and its major role is lithotripsy for difficult stones. We also understand that use of POC is currently limited by technical difficulty or expense. However, when these challenges are overcome, direct endoscopic visualization by POC will be more suitable than balloon-occluded cholangiography for diagnosis of residual stones. Direct POC using an ultraslim endoscope does have the advantage of allowing physicians to locate the exact position of the residual bile duct stone and to remove it under direct visualization. Direct visualization of the common bile duct (CBD) using POC is more useful in patients with recurrent CBD stones and bile duct dilatation, which are risk factors for other bile duct lesions. High quality POC may, therefore, make it possible to identify residual bile duct stones, as well as precancerous lesions and/or early cancer of the bile duct, which can have a decisive impact on patient prognosis. Thus, the continued development of more convenient and high quality POC systems will advance the diagnosis and treatment of bile duct diseases.

• References

• 1 Lee YN, Moon JH, Choi HJ et al. Direct peroral cholangioscopy using an ultraslim upper endoscope for management of residual stones after mechanical lithotripsy for retained common bile duct stones. Endoscopy 2012; 44: 819-824
• 2 Cheon YK, Lehman GA. Identification of risk factors for stone recurrence after endoscopic treatment of bile duct stones. Eur J Gastroenterol Hepatol 2006; 18: 461-464
• 3 Itoi T, Sofuni A, Itokawa F et al. Evaluation of residual bile duct stones by peroral cholangioscopy in comparison with balloon-cholangiography. Dig Endosc 2010; 22: S85-S89
• 4 Tsuchiya S, Tsuyuguchi T, Sakai Y et al. Clinical utility of intraductal US to decrease early recurrence rate of common bile duct stones after endoscopic papillotomy. J Gastroenterol Hepatol 2008; 23: 1590-1595
• 5 Ang TL, Teo EK, Fock KM, Lyn TanJY. Are there roles for intraductal US and saline solution irrigation in ensuring complete clearance of common bile duct stones?. Gastrointest Endosc 2009; 69: 1276-1281
• 6 Kim HI, Moon JH, Choi HJ et al. Holmium laser lithotripsy under direct peroral cholangioscopy by using an ultra-slim upper endoscope for patients with retained bile duct stones (with video). Gastrointest Endosc 2011; 74: 1127-1132
• 7 Itoi T, Moon JH, Waxman I. Current status of direct peroral cholangioscopy. Dig Endosc 2011; 23 Suppl 1: 154-157
• 8 Moon JH, Ko BM, Choi HJ et al. Direct peroral cholangioscopy using an ultra-slim upper endoscope for the treatment of retained bile duct stones. Am J Gastroenterol 2009; 104: 2729-2733
• 9 Choi HJ, Moon JH, Ko BM et al. Clinical feasibility of direct peroral cholangioscopy-guided photodynamic therapy for inoperable cholangiocarcinoma performed by using an ultra-slim upper endoscope (with videos). Gastrointest Endosc 2011; 73: 808-813