Hepatic excretion of urographic contrast medium: use in delineating intrahepatic cholangiocarcinoma on scans delayed for 2 hours.

Vicarious excretion of urographic contrast media by the liver has been detected by conventional radiographic methods in patients with renal impairment or unilateral obstruction. It occurs in patients with normal renal function, however, and can be detected by delayed postcontrast computed tomography scans. A case is presented in which an intrahepatic cholangiocarcinoma was best depicted on scans delayed for 2 hours. After 2 hours, the contrast medium remained within hepatic parenchyma but was virtually cleared from the vascular and interstitial spaces.