いわゆる側方発育型大腸腫瘍における治療法選択のための高周波超音波内視鏡検査の有用性

Efficacy of a High-Frequency Ultrasound Probe for Determining the Therapeutic Strategy for Laterally Spreading Tumors

要旨

　いわゆる側方発育型大腸腫瘍（LST）117病変における高周波細径プローブ（HFUP）の深達度診断能について検討した．腫瘍径別の検討では，30mm未満の病変が，肉眼型別の検討では，顆粒均一型の深達度正診率が高かった．腫瘍径・肉眼型の組み合わせで検討すると，深達度正診率は，顆粒均一型（100％），30mm未満の結節混在型（90.9％），20mm未満のpseudo-depressed type（88.9％），flat elevated type（81.8％）の順で診断能が良好であった．誤診例27例（23.1％）の検討では，その平均腫瘍径は誤診群がより大きく，誤診原因は描出不良（10例），深部減衰（7例），線維化（4例）などであり，肉眼型では結節混在型が多かった．以上の結果から，HFUPの診断能は腫瘍径と肉眼型に規定され，描出不良例と深部減衰例に対する克服が課題であると考えられた．

　We retrospectively studied the diagnostic accuracy of the high-frequency ultrasound probe (HFUP) for invasion depth of colorectal laterally spreading tumors (LSTs), used in 117 such tumors. The macroscopic type was classified into 4 types ; homogeneous type, nodular mixed type, flat elevated type and pseudo-depressed type. The diagnostic accuracy is higher in LSTs measured less than 30mm in diameter than in those measured more than 30mm in size. The diagnostic accuracy rate for the homogeneous type was highest among the four types. When investigating the accuracy rate of diagnosis of LSTs by the combination of tumor size and the macroscopic types, HFUP diagnosed 100％ in the homogeneous type, 90.9％ in the nodular mixed type less than 30mm in size, 88.9％ in the pseudo-depressed type less than 20mm in size and 81.8％ in the flat elevated type. The mean tumor size which was incorrectly diagnosed was significantly larger than that of correctly diagnosed cases. Incorrect diagnosis by HFUP was found in 27 cases (23.1％), mainly caused by insufficient visualization, when the lesions existed on the colonic folds in 10 cases, ultrasound attenuation in 7 cases, and fibrosis in the submucosal layer in 4 cases. These results suggest that diagnostic accuracy of HFUP in LST depends on both tumor size and macroscopic type. Although HFUP is a useful modality for invasion depth diagnosis of LSTs, insufficient visualization and ultrasound attenuation remain problems to be resolved.