超音波内視鏡による粘膜下腫瘍の診断

Diagnosis of Gastric Submucosal Tumor (SMT) by Endoscopic Ultrasonography (EUS)

要旨　従来行われている内視鏡検査，X線検査による粘膜下腫瘍（SMT）の診断は，粘膜表面に表れた腫瘍の間接所見に基づき行われているものであり，その診断能には多くの問題点が残されていた．これに対し超音波内視鏡（EUS）は壁外部分を含む腫瘍そのものの直接所見に基づいて診断するものであり，まさに画期的な検査法である．EUSの腫瘍断層所見より，SMTと壁外圧迫との鑑別は容易に，しかも確実となり，腫瘍の正確な大きさ，由来組織，発育形態の把握が可能となった．また，その内部エコー性状より，脂肪腫，囊腫，迷入膵などの質的診断も可能である．臨床的に最も問題となる筋原性腫瘍の良悪性の鑑別については依然として問題が残されているが，SMTの診断および内視鏡的治療の適応決定において，EUSは今や必要不可欠の検査法である．

　As to the diagnosis of submucosal tumor (SMT) of the gastrointestinal tract, a newly developed diagnostic modality of endoscopic ultrasonography (EUS) has the great advantage over the conventional modalites such as endoscopy and x-ray examination.

　Owing to the transmural tomography of the wall of gastrointestinal tract, EUS has unique ability in recognizing tissue origin and growth pattern of SMT, knowing where it does come from and how it does grow, clearly visualizing the location and size, and thus differentiating it from extraluminal tumor which compresses the wall of gastrointestinal tract intraluminally from outside.

　As to the diagnostic ability of EUS, for example, a differential diagnosis among lipoma, cyst and ectopic pancreas is possible, although it still remains impossible between leiomyoma and leiomyosarcoma, which seems to the fatal and mechanical limitation inherent in this methodology EUS.

　With great and unique ability, EUS is now an indispensable diagnostic procedure for the various diseases in the field of gastroenterology, especially for SMT, providing useful information not only for the diagnosis but also for the indication of endoscopic surgery.