[Hepatic x-ray computed tomography. Value of delayed (6 hours) scanning in patients with normal biliary function]

Delayed hepatic CT (DH-CT) was studied in 250 patients without any major bile duct pathology. One hundred thirty-five of these patients had liver metastases. All patients were administrated 76 grams of iodine. Tolerance of the examination was good. Six hours after injection, average contrast enhancement in the normal liver was 24 HU (greater than 1.3 g/kg iodine), 22 HU (1 to 1.3 g/kg) and 14 HU (1 g/kg). Comparison of scans taken before, immediately after, and 6 hours post-injection revealed the frequent superiority of postinjection scans for diagnosis of liver metastases. Focal steatosis is the only benign pathology to benefit from DH-CT, because of the parallelism in the difference in density between the normal and steatotic tissue regardless of the time of scanning. Aside from isolated tumors requiring exploration by conventional CT (pre- and post-contrast studies), the workup of liver metastases can be optimized by postcontrast and DH-CT scans.