多田 俊史^{1, 2}, 飯島 尋子², 熊田 卓³

Toshifumi TADA^{1, 2}, Hiroko IIJIMA², Takashi KUMADA³

¹姫路赤十字病院内科, ²兵庫医科大学消化器内科, ³岐阜協立病院看護学部

¹Department of Internal Medicine, Japanese Red Cross Himeji Hospital, ²Department of Internal Medicine, Division of Gastroenterology and Hepatology, Hyogo Medical University, ³Department of Nursing, Gifu Kyoritsu University

キーワード : non-alcoholic fatty liver disease, B-mode ultrasound, ultrasound attenuation, ultrasound elastography

組織学的に肝細胞の5％以上に脂肪化が認められる場合に脂肪肝と定義される．特にアルコールに由来しない脂肪肝は nonalcoholic fatty liver disease （NAFLD）と総称されている．最近，NAFLDの予後は，肝線維化が重要な因子であることが報告されている．以前より脂肪肝の診断は超音波B-modeにより行われてきたが，一般的に30％以上に脂肪化が認められないと，良好な感度，特異度が得られない．最近，超音波減衰法による肝脂肪の定量評価法が可能となった．これまでの実臨床のデータから超音波減衰法により肝脂肪化5％以上の診断も可能となってきた．さらに超音波エラストグラフィによる肝線維化診断も確立してきており，脂肪肝診療において超音波の果たす役割は重要であると思われる．

Fatty liver is defined as steatosis affecting >5% of hepatocytes. Fatty liver disease, especially non-alcohol-related fatty liver, is collectively referred to as non-alcoholic fatty liver disease (NAFLD). Recently, it has been reported that liver fibrosis is an important factor in the prognosis of NAFLD. Although B-mode ultrasound has been used to diagnose fatty liver disease, good sensitivity and specificity are generally not achieved unless more than 30% of the liver is found to be fatty. Recently, quantitative evaluation of steatosis using ultrasound attenuation has become available. Based on real-world clinical data, it is now possible to diagnose steatosis affecting >5% of hepatocytes using ultrasound attenuation. In addition, the diagnosis of liver fibrosis using ultrasound elastography has been established, and the role of ultrasound in the clinical setting of fatty liver is important.