超音波断層法(US)による早期胆嚢癌の診断―その可能性と限界

Early Diagnosis of Gallbladder Cancer Using Conventional Ultrasonography as a Screening Filter

要旨　腹部超音波断層法が早期胆囊癌診断に果たす役割，特にそのスクリーニング能と診断限界について検討した．1983年4月から1985年12月までに，京都第二赤十字病院のドックを受診した8,900名のうち超音波断層検査で胆囊に何らかの異常を指摘されたものは1,139名（12.8％）で，このうち胆囊小隆起性病変を指摘されたものは718名（8.1％）であった．過去5年間に胆摘術を施行された686例中30mm以下の隆起性病変を認めたものは，胆囊癌6例を含む60例であった．31例はcholesterol polypで93.5％が10mm以下の小病変であったが，6例の胆囊癌症例中3例は10mm以下の小病変で，大きさによる質的診断は困難であった．このため60例中USで描出された55例について病変の超音波断層像を5型に分類し，組織所見と対比した．その結果，胆囊癌を含むadenomaとadenomyomatosisは乳頭状実質エコー像と結節状実質エコー像を示した．以上，US検査は早期胆囊癌診断に十分なスクリーニング検査能を持つが，精密検査を要する超音波断層像の検討と共に，注意深い病変断層像の観察と解析が不可欠と考えられた．

　Through recent progress of ultrasonography for digestive diseases, we can get an exact diagnosis of the gallbladder lesions easily. In this paper, the usefulness of ultrasonography as a screening filter for the early diagnosis of gallbladder cancer is discussed.

　From April in 1983 to December in 1985, the hepato-pancreato-biliary organs of 8,900 persons, who came to our hospital for health examination, were examined by ultrasonography. As a results of the health examination, gallstone was detected in 367 persons (4.1%). Polypold lesion was detected in 718 persons (8.1), Sixty cases of gallbladder polypoid lesion under 30 mm in size were examined histologically in 686 cases of cholecystectomy in the past five years.Comparing the size of the polypoid lesion with respective histological findings, it was confirmed that histological findings have no relation to the size of the lesions. For example, in the six cases of gallbladder cancer, three lesions were smaller than 10 mm in diameter.

　Ultrasonograms of 55 cases of gallbladder polypoid lesions were compared with their respective histological findings, and the ultrasonograms were devided into five groups, Type I: foamy high echogram, Type II: globular high echogram, Type III: papillary high echogram. Type IV: papillary solid echogram, Type V: nodular solid echogram. The echograms of adenocarcinoma and adenomyomatosis were detected, showing the echogram type IV or type V, except for one case of adenoma showing type III. It was impossible to make a differential diagnosis of these three diseases from ultrasonographic findings. Ultrasonogram of early gallbladder cancer in five cases (six lesions) showed the echogram type IV in two cases and type V in three cases.

　Thus, conventional ultrasonography is the most useful method as a screening filter for the early diagnosis of gallbladder cancer.But there is a limitation to the usefulness of conventional ultrasonography in diagnosing the quality of the small polypoid lesions and in the differentiation between benign and malignant lesions of gallbladder polyps.