Bile duct angulation and tumor vascularity are useful radiographic features for differentiating pancreatic head cancer and intrapancreatic bile duct cancer

Background and purpose To perform radical resection without leaving residual cancer, surgeons must distinguish between pancreatic head cancer (PHC) and intrapancreatic bile duct cancer (IPBDC) preoperatively. The aim of this study was to establish the points of difference between these two cancers, especially on preoperative multi-detector computed tomography (MDCT) images. Methods The subjects of this study were 28 patients with PHC and proven bile duct invasion who underwent pancreatoduodenectomy (PHC group) and 22 patients with IPBDC and upstream bile duct dilation (IPBDC group). We compared the preoperative clinical and radiographic features, including the bile duct angle, calculated on coronal images of MDCT, and the vascularity of the tumor. Results The optimal cut-off values for the bile duct angle, the CT value ratio of the tumor (late arterial phase/non-enhanced), and the main pancreatic duct (MPD) ratio (diameter of MPD/diameter of parenchyma) were 110 degrees, 3.0, and 0.2, respectively. Multivariate analysis revealed that a bile duct angle < 110 degrees, a CT value ratio of the tumor < 3, and an MPD ratio >= 0.2 were independently associated with PHC. Conclusions A bile duct angle and CT value reflecting the vascularity of the tumor might be useful radiographic features for differentiating PHC and IPBDC, in addition to MPD dilatation.