The role of intraductal ultrasound in endoscopic biliary brushing for sampling in patients with malignant biliary strictures: a bicentric retrospective study.

Background: Endoscopic biliary brushing is the first line modality for sampling in patients with indeterminate biliary stricture (BS); however, its sensitivity is limited. Endoscopic intraductal ultrasound (IDUS) is also a useful approach for the diagnosis of biliary malignancies. However, whether IDUS can guide the sampling by biliary brushing has not been reported.

Methods: We retrospectively analyzed patients who underwent endoscopic retrograde cholangiopancreatography for BS in 2 tertiary care hospitals and assessed the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of IDUS and brush cytology.

Results: The study involved 530 patients with BS, including 333 in the IDUS group and 197 in the non-IDUS group. Both groups exhibited similar baseline characteristics. The diagnostic ability of IDUS imaging was as follows: sensitivity 70.7%, specificity 82.4%, PPV 81.5%, NPV 72.0%, and accuracy 76.3%. Brush cytology alone demonstrated an overall sensitivity of 45.2%, with specificity 98.2%, PPV 97.2%, NPV 56.0%, and accuracy 67.2%. The sensitivity was similar in patients with or without IDUS, whereas it was significantly higher in patients with biliary mucosal invasion indicated by IDUS (55.1% vs. 30.3%, P=0.003).

Conclusion: Although IDUS cannot improve the detection rate of biliary brushing for malignancy, it helps identify patients with malignant BS to be sampled more easily by brushing.