CT OF AGENESIS AND ATROPHY OF THE RIGHT HEPATIC LOBE

Background: To identify and differentiate agenesis and severe atrophy of the right hepatic lobe on computed tomography (CT). Methods: The CT examinations of three cases of agenesis and 11 cases of severe atroph y of the right hepatic lobe were reviewed. We evaluated visibility of the three hepatic veins, the two main portal veins (including their br anches if necessary), the dilated intrahepatic ducts, enlargement of t he medial and lateral segments of the left lobe and caudate lobe of th e liver, presence of a retrohepatic gallbladder, hyperattenuation of t he atrophic liver parenchyma, posterolateral interposition of the hepa tic flexure of the colon, and upward migration of the right kidney. Re sults: In the three cases of agenesis, no structure can be recognized as the right hepatic vein, right portal vein, or dilated right intrahe patic ducts. In the 11 cases of severe lobar atrophy, the right portal vein (or its branches) was recognized in eight cases, the right hepat ic vein in four cases, and the dilated right intrahepatic ducts in 11 cases. The degree of enlargement of the lateral segment does not neces sarily change inversely with the size of the medial segment and the ca udate lobe. The retrohepatic gallbladder is present in eight cases (tw o in agenesis and six in atrophy). The phenomenon of hyperattenuation of the atrophic liver parenchyma was noted in six cases. Conclusion: E ven though a retrohepatic gallbladder and a severely distorted hepatic morphology due to compensatory hypertrophy of the left and caudate lo bes may raise a suspicion of agenesis of the right lobe of the liver, absence of visualization of all of the right hepatic vein, right porta l vein and its branches, and dilated right intrahepatic ducts is a pre requisite of the diagnosis of agenesis of the right hepatic lobe on CT . In severe lobar atrophy, at least one of these structures is recogni zable.