伝法 秀幸¹, 斎藤 聡², 窪田 幸一¹, 宇賀神 陽子¹, 竹内 和男³, 井上 雅文⁴

Hideyuki DENPO¹, Satoshi SAITOH², Koichi KUBOTA¹, Yoko UGAJIN¹, Kazuo TAKEUCHI³, Masafumi INOUE⁴

¹虎の門病院分院臨床検査部, ²虎の門病院肝臓センター, ³虎の門病院消化器内科, ⁴JCHO東京新宿メディカルセンター病理診断科（元虎の門病院病理部）

¹Department of Clinical Laboratory, Toranomon Hospital, ²Department of Hepatology, Toranomon Hospital, ³Department of Gastroenterology, Toranomon Hospital, ⁴Department of Diagnostic Pathology, Japan Community Health care Organization Tokyo Shinjuku Medical Center

キーワード : ultrasound, fatty liver, hepatic steatosis, NAFLD activity score, focal spared area

目的：近年の機器の進歩により，脂肪肝における各Bモード所見の出現頻度が変化している．また，non alcoholic fatty liver disease activity score（NAS）では組織脂肪化を5％以上と分類しているため，Bモードでの各脂肪化所見に関して，NASの脂肪化分類に準拠し検討を行った．対象と方法：肝組織診断と超音波検査を施行した75症例．東芝製Aplio XGを使用しBモードの脂肪化所見である肝腎コントラスト，bright liver, 深部減衰の増強，脈管不明瞭化に加え限局性低脂肪化域の出現頻度とNASの脂肪化分類を比較検討した．結果：NASとUS脂肪肝の比較；肝腎コントラストおよびbright liverの両方を認める例，ないしはそれらの所見が軽微な場合，限局性低脂肪化域を併せて認める例をUS脂肪肝とすると，NAS脂肪化分類のGrade0/1/2/3（S0‐3）では0％/52％/100％/100％がUS脂肪肝となった．また，5‐33％の軽度脂肪化例では組織脂肪化を5‐10％/11‐20％/21‐33％に細分類すると，21％/88％/100％がUS脂肪肝となった．Bモードでの各脂肪化所見の有無；高度脂肪肝の所見である深部減衰の増強はS2:10％/S3:75％，脈管不明瞭化はS2:0％/S3:38％に認められ，限局性低脂肪化域はS1/2/3では32％/70％/88％と高度になるにつれ認められた．まとめ：機器の進歩により深部減衰の増強と脈管不明瞭化の出現頻度は減少した．また，bright liver，肝腎コントラストはもちろんのこと，限局性低脂肪化域の所見も重要であり，10％程度の軽度脂肪化から指摘可能と考えられた．

Purpose: Due to advances in the technology, the frequencies of appearance of each of the B-mode findings that are characteristic to the fatty liver are changing. In addition, because fatty changes in tissues are classified as a surface area of 5% or greater according to the non-alcoholic fatty liver disease activity score (NAS). we investigated each of the fatty change findings observed during the B-mode imaging. Patients and Methods: We investigated 75 patients who underwent a hepatic cytology and an ultrasound (US) imaging using a Toshiba Aplio XG. We performed a comparative investigation between the frequency of fatty change findings on B-mode images, such as hepato-renal echo contrast, bright liver, enhanced deep attenuation, vascular blurring, and focal spared area, and NAS fatty change classification. Results: A comparison between NAS and fatty liver on US imaging showed that if subjects had both hepato-renal echo contrast and bright liver or if these findings were mild and when the fatty liver on US imaging showed aforementioned findings along with focal spared area, then the NAS fatty change classification of grade 0/1/2/3 (S 0-3) corresponded to 0%/52%/100%/100% of the fatty liver tissue observed, respectively. In addition, in subjects with mild fatty changes of 5%-33% or less, fatty changes in tissues were subdivided into 5%-10%/11%-20%/21%-33%, which corresponded to 21%/88%/100% of the fatty liver tissue observed, respectively. The presence of each fatty change finding on B-mode images is as follows: Enhanced deep attenuation, a finding indicative of high-grade fatty liver, was present in S2: 10%/S3: 75%, while vascular blurring was observed in S2: 0%/S3: 38% and focal spared area was observed in S1/2/3 in 32%/70%/88%, respectively. Conclusion: The frequency of observation of enhanced deep attenuation and vascular blurring has decreased. In addition, the findings such as bright liver and hepato-renal echo contrast as well as focal spared area are important because these findings can indicate mild fatty changes involving 10% of the liver.