CT evaluation of paraaortic lymph node metastasis in patients with biliary cancer

Background. The extent of paraaortic lymph node (PAN) metastasis parellels that of distant metastases in patients with biliary carcinoma. Accurate preoperative assessment of PAN metastasis has a crucial impact on surgical indications. In this retrospective study, we evaluated whether computed tomography (CT) scans were useful for diagnosing PAN metastases and excluding patients with PAN metastases from an indication for surgery. Methods. Between March 1999 and November 2003, 57 patients with biliary carcinoma underwent radical lymphadenectomy or surgical biopsy of PANs. Nine of these patients were diagnosed as having PAN metastasis microscopically. All patients had undergone abdominal CT scans before surgery. To diagnose PAN metastases, we used the following diagnostic criteria. (1) Size; when lymph nodes were greater than 12mm, 10mm, 8mm, or 6mm in longo or short-axis diameter, the nodes were considered metastatic. (2) Shape and size; when the axial ratio of a lymph node was greater than 0.5, 0.7, 1.0, and the maximum diameter of the long or short axis was greater than 12mm, 10mm, 8mm, or 6mm, the node was considered metastatic. (3) Internal structure; if the internal structure of a PAN was heterogeneous, the node was considered metastatic. A positive predictive value was calculated for each included criterion when patients numbered ten or more. Results. Positive predictive values using the above criteria ranged from 13% to 36%. Only one patient had PANs with heterogeneous internal structures. Conclusion. We were unable to determine surgical indications based on the morphological criteria revealed by a CT scan.