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 extension from that caused by inflammation after placing a biliary catheter on intraductal ultrasonography (IDUS).

METHODS: We studied 51 patients with biliary tract malignancies who had undergone placement of biliary drainage catheters before IDUS. IDUS was performed from a transhepatic (n = 34) or transpapillary (n = 17) route with a thin-caliber ultrasonic probe (2.0 mm in diameter, 20-MHz frequency). At the hepatic side of the tumor, the thickness, asymmetry, outer margin, inner margin, and internal echoes of the bile duct wall were reviewed prospectively and correlated with the histologic findings of the surgically resected specimens in all cases.

RESULTS: When IDUS showed wall thickening in a semicircular fashion, notched outer margin, rigid inner margin, papillary inner margin, and heterogeneous internal echoes, each finding had a positive predictive value for diagnosing cancer extension (100%, 100%, 83%, 100%, and 90%, respectively). When these factors were used as the diagnostic criteria of cancer extension, IDUS 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 specific for cancer extension. However, surgical margins can be inaccurately assessed in some patients.