竹内 啓人¹, 杉本 勝俊¹, 大城 久², 岩塚 邦生³, 河野 真¹, 吉益 悠¹, 笠井 美孝¹, 古市 好宏¹, 坂巻 健太郎⁴, 糸井 隆夫¹

Hirohito TAKEUCHI¹, Katsutoshi SUGIMOTO¹, Hisashi OSHIRO², Kunio IWATSUKA³, Shin KONO¹, Yu YOSHIMASU¹, Yoshitaka KASAI¹, Yoshihiro FURUICHI¹, Kentaro SAKAMAKI⁴, Takao ITOI¹

¹東京医科大学臨床医学系消化器内科学分野, ²自治医科大学附属病院病理診断科, ³日本大学病院消化器病センター消化器内科, ⁴東京大学大学院医学研究科生物統計情報学講座

¹Department of Gastroenterology and Hepatology, Tokyo Medical University, ²Department of Pathology, Jichi Medical University, ³Division of Gastroenterology and Hepatology, Department of Medicine, Nihon University School of Medicine, ⁴Department of Biostatistics and Bioinformatics, Graduate School of Medicine, University of Tokyo

キーワード : shear wave elastography, ultrasound, FIb4 index, NAFLD

目的：Shear wave elastography（SWE）は，B型およびC型慢性肝炎で有効性が実証されているが，非アルコール性脂肪肝疾患（non-alcoholic fatty liver disease: NAFLD）の場合には有効性は限定的である．本研究は，肝生検によりNAFLDの確定診断を受けた患者に対し，SWEおよびFIB4 indexの精度を評価し，SWE測定に関するその他の組織学的パラメーターの影響を評価することを目的とした．方法：本研究は当施設の倫理委員会の承認を受けて行った．組織学的にNAFLDと診断された71名の患者（平均年齢50.8歳±15.7歳）を対象に調査した．患者全員にSWE（Aixplorer; SuperSonic Imagine）を用いて肝硬度測定を行い，FIB4 index（年齢，AST，ALT，血小板数に基づく）の測定を行った．SWE測定値は，NAFLD activity score（NAS）とFIB4 indexに基づいて組織学的特性と比較を行った．結果：肝線維化stage 3以上の診断で見られるROC曲線下の面積は，SWEの場合0.821（最適Cut off値13.1 kPa，感度62.5％，特異度57.4％）で，FIB4 index（最適Cut off値1.41，感度71.9％，特異度53.9％）の場合は0.822であった．SWEを使用して測定した肝硬度の中央値は，肝線維化stage（P ＜ 0.001），炎症grade（P ＝ 0.018），風船様腫大grade（P ＜ 0.001）が上昇するにつれて，段階的に上昇し，肝脂肪化gradeが上がるにつれて段階的に上昇した（P ＝ 0.046）．結論：SWEおよびFIB4 indexは，NAFLD患者の肝線維化stageを推定するのに役立つ非侵襲的方法である．しかし，重度の肝脂肪化の存在下では肝硬度測定に影響を及ぼし，肝線維化stageが過小評価される場合がある．

Purpose: Shear wave elastography (SWE) has been validated in chronic hepatitis C and B; however, limited data are available in non-alcoholic fatty liver disease (NAFLD). This study aimed to evaluate the accuracy of SWE and FIB4 index for the diagnosis of fibrosis in a cohort of consecutive patients with biopsy-proven NAFLD, and to evaluate the effects of other histologic parameters on SWE measurement. Methods: Written informed consent was obtained from all patients, and this study was approved by our internal review board and ethics committee. Seventy-one patients with histologically proven NAFLD (mean age 50.8 years ± 15.7) were examined. All patients underwent SWE (Aixplorer; SuperSonic Imagine) and FIB4 index (based on age, aspartate aminotransferase and alanine aminotransferase levels, and platelet counts) measurements. SWE measurements were compared with the histologic features based on the NAFLD activity score and FIB4 index. Results: The area under the ROC curve for the diagnosis of hepatic fibrosis stage 3 or higher was 0.821 (optimal cut-off value 13.1 kPa, sensitivity 62.5%, specificity 57.4%) for SWE and 0.822 (optimal cut-off value 1.41, sensitivity 71.9%, specificity 53.9%) for FIB4 index. The median liver stiffness values measured using SWE showed a stepwise increase with increasing hepatic fibrosis stage (P ＜ 0.001), inflammation score (P = 0.018), and ballooning score (P ＜ 0.001), and showed a stepwise decrease with increasing hepatic steatosis stage (P = 0.046). Conclusions: SWE and FIB4 index are useful noninvasive tools for estimating the severity of fibrosis in NAFLD patients. However, the presence of severe steatosis may affect the liver stiffness measurement, resulting in underestimations of liver fibrosis.