IDDF2024-ABS-0332 Comparison between endoscopic retrograde cholangiopancreatography guided brush cytology (ERCP-BC) and single operator cholangioscopy (SOC) guided biopsy in diagnosis of indeterminate hilar biliary strictures

<h3>Background</h3> Indeterminate biliary strictures pose a diagnostic challenge. The main reason for this has been the inability to obtain adequate tissue from the site of the biliary stricture. ERCP, along with brush cytology (ERCP-BC), has been the traditional method of obtaining cytology specimens but has been found to have poor sensitivity. Cholangioscopy provides the ability to obtain biopsies under direct visualisation from these strictures. We aimed to compare the diagnostic utility of ERCP-BC and cholangioscopy and biopsy. We also correlated visual findings on cholangioscopy with benign and malignant strictures. <h3>Methods</h3> In this prospective observational study, we included patients with indeterminate biliary strictures who underwent ERCP from April 2020 to April 2021. The indeterminate biliary stricture was defined as the absence of diagnosis following cross-sectional imaging and MRCP. Patients underwent back-to-back ERCP-BC followed by cholangioscopy with biopsy during the same session. Data regarding biochemical, imaging, ERCP-BC, and SOC-guided biopsy were recorded. The appearance of the stricture on cholangiscopy was recorded. The final diagnosis of malignancy vs benign stricture was ascertained on positive pathology or on follow-up for 3 months. The diagnostic accuracy of each modality was then calculated. <h3>Results</h3> A total of 25 patients with indeterminate biliary stricture were included in the study, with a median age of 58.84 ± 15.69 years, with 36% being females. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of ERCP-BC and SOC-guided biopsy were 55.6%,100%,100%,80%,84% (p-value =0.002) and 77.8%,100%,100%,88.8%,92% (p-value &lt;0.001) respectively. Nodularity, presence of mass-like appearance, and irregular dilated vessels are seen on cholangioscopy best-predicted malignancy. Adverse events were similar in both groups. <h3>Conclusions</h3> The SOC-guided biopsy had better sensitivity and diagnostic accuracy when compared to brush cytology in the diagnosis of malignancy in indeterminate hilar strictures. SOC had the added advantage of direct visualisation of the stricture for features of malignancy.