臨床検査67巻10号

2023年10月発行

増大号 肝疾患　臨床検査でどう迫る？ 1章　肝関連検査の見方

肝臓の線維化にかかわる検査

著者： 豊田秀徳¹

所属機関： ¹大垣市民病院消化器内科

ページ範囲：P.1052 - P.1057

はじめに

　ウイルス肝炎・脂肪性肝疾患に代表されるびまん性肝疾患において，肝線維化は肝硬変および肝細胞癌をはじめとする合併症の発生リスクと密接に関連しており，肝線維化の程度を評価することはびまん性肝疾患診療における最も重要な要素の1つである．従来，肝線維化の有無・程度の評価は肝生検で採取された肝組織の病理学的評価によりなされてきており，現在でも標準的な評価法とされている．

　一方で，肝生検は侵襲的な検査であり一般的に入院が必要なこと，検査に伴う出血のリスクがあること，コストなどの問題点があり，また採取する組織は肝のごく一部であることによるサンプリングエラーの問題，病理所見の観察者間でのvariabilityの問題が以前から指摘されてきた．これらの問題点を踏まえて，昨今ではさまざまな非侵襲的な肝線維化の評価法が提唱されている．非侵襲的な肝線維化の評価は，血液検査によるものと画像検査によるものに大別される．画像検査による肝線維化評価には腹部超音波診断機器を用いた超音波（ultrasound：US）エラストグラフィや磁気共鳴画像（magnetic resonance imaging：MRI）を用いたMRエラストグラフィがあるが，いずれも診断機器を要し，ある程度術者の習熟が必要となる．

　一方，血液検査による肝線維化評価は，採血のみによる評価であり簡便である．現在さまざまな肝線維化の血清マーカーが提唱されているが，最適な血清線維化マーカーや肝線維化評価のカットオフ値はびまん性肝疾患の成因や目的により異なる場合が多いため，その使い分けには注意が必要となる．

　本稿では，肝臓の線維化にかかわる臨床検査について概説し，その特徴，使い分けについて論じたい．

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