Utility and limitations of intraductal ultrasonography in distinguishing longitudinal cancer extension along the bile duct from inflammatory wall thickening

Background: We wanted to distinguish wall thickening caused by cancer exten sion from that caused by inflammation after placing a biliary catheter on i ntraductal ultrasonography (IDUS). Methods: We studied 51 patients with biliary tract malignancies who had und ergone placement of biliary drainage catheters before IDUS. IDUS was perfor med from a transhepatic (n = 34) or transpapillary (n = 17) route with a th in-caliber ultrasonic probe (2.0 mm in diameter, 20-MHz frequency). At the hepatic side of the tumor, the thickness, asymmetry, outer margin, inner ma rgin, and internal echoes of the bile duct wall were reviewed prospectively and correlated with the histologic findings of the surgically resected spe cimens in all cases. Results: When IDUS showed wall thickening in a semi-circular fashion, notch ed outer margin, rigid inner margin, papillary inner margin, and heterogene ous internal echoes, each finding had a positive predictive value for diagn osing cancer extension (100%, 100%, 83%, 100%, and 90%, respectively). When these factors were used as the diagnostic criteria of cancer extension, ID US accurately demonstrated suitable surgical margins in 76% of all patients and 71% of patients with bile duct carcinoma. Conclusion: Wall thickening in a semicircular fashion, notched outer margin , rigid or papillary inner margin, and heterogeneous internal echoes are sp ecific for cancer extension. However, surgical margins can be inaccurately assessed in some patients.