Supplementary Material for: Diagnostic accuracy of cholangioscopy in the investigation of undetermined biliary stenosis – a retrospective study of an high volume ERCP center

Introduction: An indeterminate biliary stricture poses a difficult diagnostic and therapeutic challenge for both Gastroenterologists and Surgeons. It is estimated that 25% of patients submitted to surgery because of suspected malignant stricture have no evidence of malignancy tissue in the evaluation of the surgical specimens. Single-operator cholangioscopy enables the direct visualization of the biliary tree and the acquisition of histologic material through guided biopsies.
Methods: Retrospective study from a prospective database of patients submitted to cholangioscopy for indeterminate biliary stricture, defined as the evidence of a narrowing of the biliary tree on imaging that remained undiagnosed after the collection of histologic material by ERCP with brush cytology. We calculated the values of sensitivity (S), specificity (SP), negative predictive value (NPV) and positive predictive values (PPV) of both the optical diagnosis and histological diagnosis.
Results: Sample of 47 patients. For the optical diagnosis, we obtained the following results: S = 94.4%; SP = 89.7%; NPV = 96.3%; PPV = 85.0%. For the cholangioscopy-guided biopsies, we obtained the following results: S = 64.7%; SP = 100.0%; NPV = 77.8%; PPV = 100.0%.
Discussion: Cholangioscopy appears to be a safe and effective method in the distinction between benign and malignant biliary strictures. The distal location of the stricture did not appear to negatively influence the diagnostic yield of cholangioscopy.