CT during arterial portography for the preoperative evaluation of hepatic tumors: how, when, and why?

CT during arterial portography (CTAP) is the most sensitive technique for the detection of intrahepatic tumors. CTAP is based on portal enhancement of the liver by infusion of contrast material through the superior mesenteric artery. This technique provides clear delineation of intrahepatic vessels, allowing segmental location of tumors to be accurately determined and relationships between tumors and intrahepatic vessels to be assessed. CTAP must be limited to patients for whom noninvasive preoperative imaging examinations have shown a potential for hepatic resection. In the majority of the cases, CTAP is performed in patients with hepatic metastases from colorectal cancer, but other types of tumor (either primary or secondary) may be an indication for CTAP. Visualization of nontumorous perfusion defects is a limitation of this technique, but such defects have been well described and have characteristic locations and appearance. In difficult cases, correlation with sonographic, CT, and MR imaging findings helps characterize portal perfusion defects. CTAP data can be viewed as multiplanar and three-dimensional reconstructions that allow preoperative planning of the extent of resection and determination of the volume of the remaining liver. The use of spiral CT shows promise in the performance of CTAP.