Proximal bifurcation of hepatic artery: Novel findings on hepatic arteries demonstrated by ultrasound Doppler imaging, B-flow, and US angiography.

ABSTRACT

PURPOSE: It has generally been held that each portal branch is always accompanied by a single arterial branch in the liver. During Doppler ultrasound examination, however, we sometimes encounter a portal branch that appears to be associated with two arterial branches, a phenomenon referred to below asthis finding orthis phenomenon. Here we attempt to confirm that this finding is based on a correct interpretation of the image and to disclose its basic mechanism. MATERIAL AND METHODS: Five cases of chronic liver disease in which this phenomenon appeared were analyzed with B-flow imaging. Videotapes obtained from 30 patients who had chronic liver disease and had undergone ultrasound angiography (USAG) with arterial infusion of CO2 micro bubbles were reviewed in order to look for similar findings. Sixty-nine healthy controls were also examined with Doppler sonography for this purpose. Histopathologic specimens from 7 patients who had undergone hepatectomy (3 with hepatocellular carcinoma, 3 with metastatic tumor, and 1 with focal nodular hyperplasia) were examined to study the basic structure of the hepatic vessels. RESULTS AND DISCUSSION: Three parallel color signals (two pulsatile and one of a constant waveform) observed on Doppler examination were confirmed by the B-flow method to be three independent vessels in all five cases in which both Doppler sonography and B-flow imaging were used. In 13 (43%) of the 30 cases of USAG, two vessels along a portal branch were visualized by the inflow of micro bubbles, indicating that the two vessels were arteries. The trio of one portal and two arterial branches was also detected with Doppler sonography in 12 (17%) of the 69 healthy controls. In 10 (59%) of the 17 cases (5 of liver disease and 12 normal) that showed this finding on Doppler examination, bifurcations of the hepatic artery and portal vein were both visualized. Hepatic arterial branches were found to bifurcate slightly more proximal to the hepatic hilus than the accompanying portal branch. Histopathologic study revealed Glisson's areas that contained one portal branch and two arterial vessels in nontumorous parts of specimens from all 7 patients with hepatectomy. CONCLUSION: Two arterial branches can be demonstrated along a portal branch as a result of a more-proximal bifurcation of the hepatic artery than of the portal vein.