岡庭 信司

Shinji OKANIWA

飯田市立病院消化器内科

Department of Gastroenterology,Iida Municipal Hospital

キーワード : ultrasound, gallbladder carcinoma, differential diagnosis

超音波検査は簡易で低侵襲な検査法であるが，空気の存在によりその伝達が妨害される特性を持ち，診断能力は術者の技能に依存する．さらに，超音波検査特有のアーチファクトの存在およびその見分け方についても熟知しておく必要がある．胆嚢の腫瘍性病変においては，その超音波像を有茎性隆起型，広基性隆起型，壁肥厚型の3群に分類する．この分類は病変の鑑別診断のみならず深達度診断においても有用であり，有茎性隆起型の癌と診断出来ればその深達度は粘膜内に限局する早期癌（腺腫内癌）と考えられる．胆嚢癌との鑑別診断には，病変の大きさ，表面構造，内部エコー，病変付着部の胆嚢壁の性状などを評価することも重要である．さらに，胆嚢の腫大や胆泥の貯留あるいは虚脱といった胆嚢の異常像は潜在する胆管病変の拾い上げにも有用である．

Ultrasound (US) is a simple and noninvasive modality, but it is susceptible to interference from gas echoes, and the ability of US depends on the level of diagnostic skill of the sonographer. It is also important that the sonographer know about the characteristics of artifacts and how to remove their influence. Gallbladder lesions are arbitrarily classified into three types including pedunculated, broad based and wall-thickened (flat) types. This classification is very important not only to make a differential diagnosis but also to evaluate the depth of cancer invasion; the pedunculated lesion can be diagnosed as an early gallbladder carcinoma. In addition, we should evaluate their size, surface structure, internal echo texture, and structural changes of the gall bladder wall. These findings are also useful to discriminate carcinomas from other lesions. Furthermore, abnormal US findings of the gallbladder, which include distension with or without debris and impaired fullness, are also useful to detect occult lesions of the extrahepatic biliary tract.