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Background and Indications
To assist with the intraoperative localization of stones during bile duct exploration, the first optical choledochoscope was described by McIver in 19411 and the per oral approach was subsequently introduced in the early 1970’s. Urakami et al reported the first dedicated per oral 8.8mm cholangioscope with a working channel2-4. Continued refinement in scope diameter, up/down angulations, and optics during the ensuing 20 years has permitted the performance of cholangiopancreatoscopy(CP) through the working channel of a standard therapeutic
duodenoscope 5.
A comprehensive review of CP has recently been published6. In general, CP has been primarily utilized to evaluate equivocal fluoroscopy findings during ERCP, treat difficult biliary and pancreatic duct stones, investigate indeterminate biliary and pancreatic strictures for directed tissue sampling, and assess the extent of cholangiocarcinoma and intraductal papillary mucinous neoplasia (IPMN) prior to resection7-13. Narrow band imaging capability is under investigation14.
Biliary Stones
Per oral cholangiosocpy-directed electrohydraulic lithotripsy (EHL) achieves a high rate of success for difficult extrahepatic biliary stones with complete clearance in 83-100% of patients12, 13, and 15. See Video #1. Arya and colleagues published a retrospective series of 94 patients who had failed stone extraction by standard techniques prior to peroral choledochoscopy. Overall, the stone clearance rate was 90%, with 90% requiring one or two EHL sessions and the rest requiring three or more. One-third of patients were sub-grouped into common hepatic and intrahepatic duct stones which represented 56% of failed EHL cases. The complication rate was 17%13. Although a 100% clearance rate with no complications was reported by Farrell and colleagues, they did not re-attempt mechanical lithotripsy at their institution prior to EHL. Further, only 15% of the 75 patients referred for EHL had intrahepatic stones15. Intrahepatic bile duct stones require more intensive endotherapy. Okugawa and coworkers reported 36 consecutive patients with hepatolithiasis treated with per oral cholangioscopy-directed EHL or laser lithotripsy16. Despite a mean of 4.5 choledochoscopy sessions and adjunctive ESWL in one-third of the patients, ductal clearance was achieved in only 75% (64% complete, 11% partial). At a mean 7.8 years of follow-up, symptomatic recurrence developed in 22% and 25% of those with complete and partial clearance, respectively. In general, the effective treatment of hepatolithiasis may require combined per oral and percutaneous approaches or surgical resection17.
Biliary Strictures
Tissue sampling at ERCP is dependent upon accurate fluoroscopic localization of the lesion or stricture. Overall, the sensitivity of ERCP tissue sampling for detecting malignancy varies from 30% to 70%18, 19. Cholangioscopy permits evaluation of equivocal fluoroscopy findings and detailed inspection of biliary epithelium to detect dysplastic or metaplastic changes (See Video #2). In the setting of biliary malignancy, cholangioscopy guides tissue sampling by assessing for “tumor vessels” (i.e. irregularly dilated and tortuous vessels), intraductal nodules or masses, infiltrative or ulcerated strictures, and papillary or villous mucosal projections20, 21. Sensitivities in detecting cholangiocarcinoma in one cohort study of patients with known cancer was 100% for the polypoid-type, 95% for the stenotic-type, 100% when a tumor vessel was noted, but only 60% for pancreatic cancer obstructing the bile duct22. Tissue samples obtained from the margins and not from within strictures improved the histological diagnosis rate of stenotic-type cholangiocarcinoma from 70% to 100%. Although the cholangioscopic visualization of tumor vessels may help predict malignancy, in one study of 63 patients with biliary strictures, tumor vessels were present in only 61% of histologically proven malignancies but when combined with percutaneous biopsy diagnosed 96% of cancers22. The negative predictive value of tumor vessels based on 1-year follow-up was 100%. Prospective studies have shown that cholangioscopy visualization with and without biopsy has a sensitivity of 89% to 100% and specificity of 87% to 96%7, 9. See Video #3. Six-month follow-up data using the Spy Glass Direct Visualization system TM (Boston Scientific, Inc.) has shown a 71% sensitivity and 100% specificity for the detection of malignancy23.
The largest per oral cholangioscopy series for the evaluation of biliary strictures is from Fukuda and coworkers who evaluated 97 patients9. Adding cholangioscopy visualization, which preceded ERCP tissue sampling, increased the accuracy of detecting malignancy from 82% to 95%. We subsequently reported the largest consecutive series of per oral CP-directed biopsy7. Unlike the study by Fukuda et al, two-thirds of the 62 patients in our cohort had previous non-diagnostic tissue sampling, and 58% had epithelial changes that prompted CP-directed biopsy. At a mean follow-up of one year, 16 of the 18 confirmed malignancies were diagnosed by CP. Initial histology obtained by either CP-directed or -assisted biopsies confirmed malignancy in 10 of 16 (63%) patients. Overall, CP+/- biopsy for detection of malignancy had a sensitivity of 89% and a specificity of 96%, with positive and negative predictive values of 89% and 96%, respectively7.
Primary Sclerosing Cholangitis (PSC)
In a series from Germany, 53 PSC patients underwent cholangioscopic visualization of dominant biliary strictures to compare its yield to cholangiography in predicting malignancy. Two endoscopists were blinded to the respective images. Malignant cytology or histology was obtained either at index cholangioscopy or at subsequent ERCP in 12/53 (23%) patients: eight at the hepatic bifurcation and four in the common bile duct. Cholangioscopy visualization, when compared with cholangiography, increased the sensitivity for detecting malignancy from 66% to 92% (p=NS) and specificity from 51% to 93% (p<.001)24. However, their cohort had a remarkably high percentage of patients with intraductal masses (9 of 12), which we did not find in our earlier study of 41 consecutive patients with PSC8. In our series, one patient had an extrahepatic infiltrative-type cholangiocarcinoma detected by cholangioscopy-directed biopsy but another patient with intrahepatic cholangiocarcinoma was missed by cholangioscopy and found only in the explanted liver. However, we did find an improved detection of occult stones. See Video #4. Cholangioscopy detected stones missed by cholangiography in one-third of PSC patients8. Per oral cholangioscopy likely improves the evaluation of dominant extrahepatic and bifurcation strictures but its usefulness is limited in PSC patients with intrahepatic bile duct cancer due to the inability to access small ducts and strictures with currently available scopes.
Pancreatic Stones and Neoplasia
For the treatment of pancreatic duct stones, small case series of intraoperative EHL followed by decompressive surgery (N=10)25, per oral pancreatoscopy with EHL and ESWL (N=6)26 and preliminary data without routine use of ESWL (N=27)27 have shown complete main duct clearance rates of 100%, 50%, and 59%, respectively, with symptom improvement in the majority of patients with complete or partial clearance. For the evaluation of pancreatic strictures, a study that included 115 patients with a minimum 2-year follow-up found pancreatoscopy detected 63% of pancreatic cancers, 80% of benign strictures, and 95% of IPMN lesions28. Neoplasia assessment was based on the presence of coarse mucosa, submucosal protrusion, friability, tumor vessel, and papillary projections (see Video #5). In distinguishing benign from malignant IPMN, the endoscopic visualization of fish-egg like, villous, and prominent mucosal protrusions have been described to correlate with malignant lesions with a sensitivity and specificity of 68% and 87%, respectively, with lower sensitivity for branch-type compared to main duct lesions29. Several studies have compared per oral pancreatoscopy with intraductal ultrasound, CT, EUS, and pancreatography for distinguishing benign from malignant IPMN lesions29-31. Pancreatoscopy for main duct IPMN lesions with 3-4mm projections indicative of malignancy had a sensitivity of 67% - 100% compared to 16%-32% for CT, 56%-100% for IDUS and 55% - 92% for EUS29-31. In general, the technologies are complementary.
Summary
Cholangioscopy with intraductal lithotripsy has become an established modality in the treatment of difficult biliary stones. When used in the evaluation of indeterminate biliary strictures by endoscopists experienced in recognizing intraductal pathology, it increases the diagnostic yield of tissue sampling. Pancreatoscopy is complementary to other imaging modalities in the evaluation of IPMN and remains investigational in the diagnosis of pancreatic adenocarcinoma and the treatment of pancreatic duct stones. However, scope fragility, costs of repair, procedure time, and additional personnel, has previously discouraged its widespread use7. Current commercially available cholangioscopes have limited tip deflection and suboptimal irrigation capabilities that may be overcome with the single-operator SpyGlass Direct Visualization System TM (Boston Scientific, Inc). The disposable delivery catheter has separate dedicated irrigation channels and offers four-way tip deflection that during ex vivo laboratory simulation demonstrated improved four quadrant visualization and biopsy success rate when compared with a conventional cholangioscope23,32. For 2009, there will be a CPT code for per oral cholangiopancreatoscopy that may permit wider spread availability and use of this technology by experienced biliary endoscopists. The specific devices and techniques utilized for the performance of CP will be addressed in the 2nd part of this series.
References:
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