Extrahepatic bile duct cancer: invasion of the posterior hepatic plexuses--evaluation using multidetector CT.

PURPOSE: To assess the utility of axial and coronal reformatted multidetector computed tomographic (CT) images in the evaluation of the invasion of posterior hepatic plexuses by extrahepatic bile duct cancer. MATERIALS AND METHODS: This retrospective study was approved by the institutional review board, and informed consent was waived. Forty-three patients (22 men, 21 women; age range, 40-80 years; mean age, 65 years) with surgically resected cancer involving the extrahepatic bile duct between December 2004 and September 2010 were included. Posterior hepatic plexus 1 runs from the superior and middle bile duct to the right celiac ganglion, and posterior hepatic plexus 2 runs between the lower bile duct and right celiac ganglion behind the portal vein. Invasion of the posterior hepatic plexuses was elucidated by using pathologic and postoperative multidetector CT findings. Three radiologists independently evaluated the preoperative axial and coronal reformatted images with a separate viewing session for the invasion of posterior hepatic plexuses that was detected on the basis of the presence of increased attenuation of fat tissue along the nerve routes. Receiver operating characteristic analysis was performed to compare the diagnostic performance of the two image interpretations. RESULTS: Invasion of posterior hepatic plexus 1 and of posterior hepatic plexus 2 was recognized in 10 (23%) and nine (21%) of 43 patients, respectively. The diagnostic performance of coronal reformatted image interpretation was significantly greater than that for axial image interpretation (mean area under the curve, 0.99 vs 0.89, P = .04; mean accuracy, 95% vs 82%, P = .003). In all reviewers, one false-positive diagnosis of the invasion of posterior hepatic plexus occurred on axial and/or coronal image display types because of fibrosis and inflammatory cell infiltration along these plexus routes. CONCLUSION: Coronal reformatted images can be useful for accurate diagnosis of the invasion of posterior hepatic plexuses and may facilitate surgical decision making in regard to the resection of celiac ganglion.