微小表面型大腸腫瘍のX線診断―その基礎と診断の解析

Diagnostic Basis and Analysis of X-ray Examination on Early Superficial Colorectal Neoplasm

要旨　5mm以下の表面型大腸腫瘍119例128病変（表面隆起型78病変，表面平坦型3病変，陥凹をみる型47病変）のうち陥凹をみる型を主な対象とし，X線の立場で拾い上げ診断の現状と撮影手技を検討した．また，得られた病理割面像の解析から臨床像（X線像・内視鏡像）の分析も同時に行った．ルーチンX線検査を施行した陥凹をみる型46病変のうち13病変（28.3％）を拾い上げ，後のX線像の見直しで発見した病変を含めると計22病変（47.8％）を描出した．また，腹臥位撮影がなくしては診断できなかったものが8病変（25.0％）あった．中心陥凹の描出には"網の目像"の描出は必須条件ではなかった．病理割面像を解析すると，内視鏡的粘膜切除術で得られた材料は非生理的に過伸展された状態であった．この条件下で，臨床像との評価に耐えうる病理割面像は表面型腫瘍全体の60.9％で，更にこの中でも臨床像との一致をみたものは61.5％（表面隆起型61.5％，表面平坦型50.0％，陥凹をみる型64.9％）であった．陥凹をみる型のうち，いわゆる相対的陥凹の病変がその多くを占め，胃のⅡcとは形態的に異なった．また，臨床像（X線像・内視鏡像）から腫瘍の拡がりを確実に認識することは未だ内視鏡的検査でも難しい．X線検査は総合的な診断では内視鏡検査に劣るが，拾い上げ診断には寄与するところが大きい．X線診断の領域は，経過を追求できる像を残すことと，その客観性のある像の解析にある．

　We analyzed 128 lesions from 119 patients with minute superficial epithelial colonic neoplasms(smaller than 5 mm in size) on fixed specimens between February of 1990 and February of 1992. The purpose of this paper is to evaluate the specificity of x-ray diagnosis on these lesions. The lesions were classified as 78 superficial and elevated, 3 superficial but flat and 47 nonelevated. The superficial depressed type can be divided into 3 subtypes: 1) slightly elevated lesion with central depression, 2) depression with marginal elevation, 3) absolute depression. The difference in shape and size among x-ray, endoscopic and microscopic examinations are discussed. Procedural techniques to demonstrate the lesions on x-ray examination were also discussed.

　Out of 46 lesions, only 13 depressed lesions (28.3%) were detected by routine barium enema examination. After reviewing these x-ray films, 22 lesions (47.8%) were pointed out. In 8 cases of depressed type, only prone positioned films revealed the lesions. It is not necessary to demonstrate a fine network pattern to detect centrally depressed lesions.

　Microscopic examination showed the strip biopsized specimens were usually too stretched out at fixation. Only 61.9% of the sespecimens could be analyzed, and 61.5% of the analyzed specimens were compatible with the clinical features. On microscopic examination, most early colorectal carcinomas were relatively depressed, which is quite different from type Ⅱc early gastric caner. One of the benefits of x-ray examination is to keep the permanent images of lesions which enable us to follow them afterward. If these images are of sufficient quality, we may be able to analyze them in a timely fashion in the future.