和久井 紀貴, 松清 靖, 住野 泰清

Noritaka WAKUI, Yasushi MATSUKIYO, Yasukiyo SUMINO

東邦大学医療センター大森病院消化器内科

Department of Gastroenterology and Hepatology, Toho University Omori Medical Center

キーワード : liver fibrosis, chronic liver disease, contrast-enhanced ultrasonography, arrival time parametric imaging, Sonazoid

肝臓は他の臓器と異なり，門脈と肝動脈という2つの血管から血液が供給されている．その流入血液量の割合は約7‐8割が門脈由来で肝細胞に栄養や様々な物質を供給し，約2‐3割が肝動脈由来で主に胆道系の栄養を司っている．動脈圧が100 mmHg以上であるのに対し，門脈圧は6‐8 mmHgときわめて低圧であるがゆえに肝病変の影響を受けやすい．肝臓はこのような2本の供給血管で賄われているが，例えばC型肝炎ウイルスに罹患すると，肝細胞の壊死・脱落・線維化を繰り返し，慢性肝炎から肝硬変へと病期が進展するに従い，門脈血流は低下し，それを補うが如く肝動脈血流が増加する．すなわち，門脈と肝動脈の肝血流バランスは病期進行に従い門脈優位から肝動脈優位へと変化するわけである．その肝血流バランスの変化を画像診断で定量的に評価が可能であれば，C型慢性肝疾患の病変進展度合いを非侵襲的に把握ができ，インターフェロン治療開始時期や合併症発現などの推測ができるため臨床的に役に立つ．筆者らはこれら肝栄養血流の動態を造影超音波（arrival-time parametric imagingingなど）で解析し，肝疾患の病態理解に役立てているため，その最新事情につき紹介する．

The liver differs from other organs in that it receives a dual blood supply from the hepatic portal vein and hepatic artery. The portal vein, which delivers nutrients and various other substances to hepatocytes, accounts for approximately 70-80% of the total hepatic blood supply. The remaining 20-30% is supplied via the hepatic artery and mainly nourishes the biliary system. Compared with a blood pressure of ＞ 100 mmHg in the hepatic artery, the pressure in the portal vein is as low as 6-8 mmHg, making the latter system susceptible to pathological changes in the liver. Despite being safeguarded by two blood supplies, when infected, for example by the hepatitis C virus, the liver undergoes cycles of necrosis, defluxion, and fibrosis. As the disease state progresses from chronic hepatitis to cirrhosis, the blood flow in the portal vein is reduced, and as if to compensate for this, the arterial blood flow increases. In other words, the hepatic hemodynamic balance between the portal vein and hepatic artery changes from portal vein dominant to hepatic artery dominant. Diagnostic imaging modalities able to quantitate the changes in the hemodynamic balance of the liver are clinically valuable because they enable noninvasive staging of hepatitis C and can be used to predict the timing of interferon treatment or the onset of complications. We have been using arrival time parametric imaging to examine the hemodynamics of the nutrient hepatic blood flow to improve our understanding of the pathological manifestations of liver diseases. Here, we introduce the latest developments in this area.