Vascular Diseases of the Liver

Vascular diseases of the liver have attracted attention in recent years as a result of several advances. Progress in noninvasive imaging has greatly facilitated recognition of diseases of the large vessels. Moreover, the scope of “cryptogenic” liver disease has shrunk with the identification of hepatitis C virus and nonalcoholic fatty liver disease among others as specific causes of cirrhosis. Therefore, the proportion of patients actually suffering from a vascular disease of the liver, among those with currently truly cryptogenic conditions, has dramatically increased. Still, vascular diseases of the liver remain rare, at least in their primary form in which the diseased vessels cause liver or biliary damage. These primary vascular diseases are the topic of this issue of Seminars in Liver Disease.

Much more frequent than primary disease is the secondary involvement of the hepatic vessels by primarily parenchymal or biliary diseases, an aspect which is not considered in this issue. The exact role that such a secondary involvement may play in aggravating the parenchymal or biliary disease remains unclear. However, it is expected that an improved knowledge of primary vascular diseases of the liver will help in understanding how vascular involvement may modulate the clinical expression or the course of primary parenchymal or biliary diseases.

Hepatic arterial disease is addressed first in a section on ischemic cholangiopathy, a consequence of a blocked arterial inflow, and also in a section on hereditary hemorrhagic telangiectasia, a disease causing arteriohepatic and arterioportal fistulas. Hepatic vein disease is discussed in the section on Budd–Chiari syndrome. Portal vein disease is considered separately with respect to the extrahepatic portal vein and small intrahepatic portal veins.

Besides advances in diagnostic modalities, advances in vascular biology have also stimulated interest in vascular diseases of the liver. In this regard, the improved characterization of prothrombotic conditions has been of major importance. A discussion of the aspects relevant to splanchnic vein thrombosis has been included in this issue, as well as the role that exposure to female hormones plays in causing vascular diseases of the liver. Liver transplantation is another field the development of which has allowed a better delineation of the role of hepatic vasculature in causing hepatic or biliary derangement, either through the analysis of the native explanted liver, or unfortunately, through the consequences of impaired vascular reconstruction. Other crucial aspects of vascular biology, involving the microcirculation, will not be found in the present issue. Indeed, they have been discussed by Laurie DeLeve in an outstanding section on Hepatic Microvasculature in Liver Injury which appeared in a recent issue of Seminars in Liver Disease devoted to the Pathogenesis of Liver Injury (November 2007 27(4): 390–401). The reader is strongly recommended to refer to this article which discusses other hepatic conditions resulting from microvascular involvement such as sinusoidal obstruction syndrome (venoocclusive disease), nodular regenerative hyperplasia, and peliosis hepatis, as a component of the current presentation.

The scope of vascular diseases of the liver would not be complete without a focus on vascular tumors of the liver, which distribute either as extremely frequent benign hemangiomas or extremely rare malignant tumors. Although focal nodular hyperplasia is a nodule-forming lesion likely resulting from an abnormal perfusion pattern, it is not discussed in this article as it is not neoplastic in nature and consists of regenerative hepatocytes, not of vascular cells.

It is the immediate hope of the authors and editors that this issue will contribute to an increased awareness of the rare, but significant vascular diseases of the liver. Increased awareness is probably the factor most likely to improve the overall outcome for these severe diseases by shortening time to recognition and to appropriate therapy. Our remote hope is that knowledge on primary vascular diseases of the liver will stimulate interest in secondary vascular involvement as a target to improve the outcome of primary parenchymal or biliary diseases.