噴門部領域の進行癌における進展・浸潤範囲の画像診断―超音波内視鏡の立場から

Assessment of Esophageal Invasion by Gastric Carcinoma through Using Endoscopic Ultrasonography

要旨　胃癌の食道浸潤の的確な術前評価は，切除術式を決定するうえで重要な問題となってくる．今回，噴門部領域の進行癌の食道浸潤の超音波内視鏡（EUS）診断の有用性について検討した．1994年1月～1996年12月の期間に当院で切除された噴門部領域を含む進行胃癌のうち，術前に食道浸潤の有無が問題となり，EUSが施行された53例を対象とした．EUSはラジアル走査式を使用，脱気水充満法または，バルーン装着法により施行，EUS所見と病理組織学的所見を対比検討した．肉眼型は3型，4型が45例を占め，また組織型は未分化型が42例であった．病理組織上食道浸潤が認められた症例のうち，EUSで食道浸潤ありと診断できた症例は27例中22例（sensitivity 81.5％），一方，食道浸潤が陰性であったものを浸潤なしと診断したものは，26例中25例（specificity 96.2％）であり，accuracy88.7％であった．食道浸潤の範囲を±1cmまでの誤差を診断一致とした場合は，一致率は83.0％（44/53例）であった．主な誤診の理由は，広範な癌の浸潤のための噴門の不明瞭化あるいは破壊による正確なEGjunctionの同定が不確実であったこと，少量の腫瘍による食道浸潤のためEUSでの認識が困難であったことなどが考えられた．

　Preoperative accurate assessment of esophageal invasion of gastric carcinoma is important from the surgical point of view. The aim of this study is to evaluate the usefulness of endoscopic ultrasonography (EUS) in the diagnosis of esophageal invasion of gastric carcinoma located in the cardiac area.

　During the period between Jan. 1994 and Dec. 1996, EUS using radial scanner with 7.5, 12 or 20 MHz was carried out in 53 patients with gastric carcinoma located in the cardiac area who underwent subsequent surgical resection. The examination of EUS was performed by the deaerated water‐filled method or the balloon method. The resected specimens were examined histopathologically and the presence or absence of esophageal invasion was also examined in detail. The ultrasonographic finding were compared with the histopathological findings of esophageal invasion.

　Histopathological invasion of the esophagus was correctly diagnosed by EUS in 22 of 27 patients (sensitivity 81.5%). On the other hand, absence of esophageal invasion was correctly diagnosed in 25 out of 26 cases (specificity 96.2%), so overall accuracy was 88.7%. When we consider that the degree of length of esophageal invasion was correct within a range of plus or minus 1 cm, the accuracy of EUS diagnosis was 83.0% (44/53 cases).

　One main reason for misdiagnosis or overestimation of the length of esophageal invasion was probably caused by the difficulty in recognizing the indistinct esophagogastric junction when remarkable cancer invasion was present.

　In conclusion, EUS is one of the methods for useful preoperative evaluation of esophageal invasion of gastric carcinoma.