Evaluation of main and right portal vein branching variations with 16-slice spiral CT

Objective To investigate the prevalence of variant main and right portal vein ramification in a large group of patients. Methods The study group consisted of 200 patients who underwent consecutive contrast-enhanced abdominal CT examinations performed with 16-MDCT scanner. Two observers evaluated both thin axial sections and 3D maximum-intensity-projection and volume-rendered images for branching patterns of the main and right portal veins. Results Conventional main portal vein anatomy was present in 64.5% of the patients. In 9.5% of the patients, the main portal vein trifurcated into the left portal, right anterior and posterior portal veins. In 23.5% of the patients, the main portal vein divided into a common left portal vein-right anterior portal vein trunk and the right posterior portal vein. Three patients (1.5%) had miscellaneous variations. Twenty-two (16.8%) of 131 patients with conventional main portal vein branching had variant right portal vein branching, most of which was a trifurcation, followed by an abnormally proximal origin of the segment Ⅶ vein from the right portal vein. Conclusion Variant main portal vein branching seems to be very frequent. Common right anterior portal vein-left portal vein trunk is far more common than trifurcation. Although less frequent, variations also occur in right portal vein branching.