ルーチン注腸X線検査における大腸癌の見逃しとその対策

Advanced Colorectal Carcinoma Missed by Radiology

要旨　1986～1991年の6年間に癌研附属病院において初回X線検査で見逃された大腸癌14症例についてその原因を検討した．見逃し部位は右側結腸11例，左側結腸3例であった．見逃しの原因は腸管収縮と造影不良が多く，腸の重なり，読影ミスがこれに続く．回盲部・上行結腸では前処置不良による造影不良が多かった．これは腸内に貯溜する水分のためにバリウムが希釈され，粘膜面への付着不良が生じたためである．横行結腸，左側結腸での見逃しの原因は鎮痙剤を使用しなかったことによって生じた腸管収縮が多かった．今回の見直しで9例に所見があり，注意深い読影が多くの見逃しを防ぐと考えられた．9例のうち7例に一側変形を認め，拾い上げにおける側面像の変形所見の重要性が再認識された．以上より，以下の結論を得た．①腸管の収縮を防ぐには鎮痙剤使用，被検者の不安・緊張の除去が必要である．②多方向から重なりを避ける撮影を行うと共に，腸管の伸展不良には，圧迫が可能であればこれを行うことによって病変の存在を否定することが必要である．このとき，大量の空気の存在は有効な圧迫や，腸管の重なりを避ける際の妨げとなりやすい．③腹部手術歴があり深部大腸の造影不良が予想される症例では，高濃度バリウムを使用するなど造影剤の工夫が必要である．④見直し診断で一側変形を認めたものが7例あり，そのうち存在診断の根拠となったものが5例あった．⑤病院診療の場においても，胃癌の集団検診における精度管理や逐年検診の手法を取り入れ，見逃しを最少限にする努力がなされるべきである．

　Retrospective review of the initial radiographic films was done to clarify the cause of oversight of advanced colorectal carcinoma, based on 14 cases which had been missed in the initial radiographic examination at the Cancer Institute Hospital in a period of 6 years from 1986 to 1991. Eleven missed cases were located in the right colon, and 3 were in the left colon.

　The most frequent causes of oversight were lumen contraction (spasm) and insufficient barium coating of the mucosa. Overlapping of the colon loop and bending, misjudgments were the next most frequent causes. Lumen contraction was observed in the cases for which antispasmodic agent was not used, and occurred most frequently in the transverse and left colon. Insufficient barium coating occurred in the ascending colon. This was caused by the dilution of barium due to the remaining fluid content in this location.

　The location of the missed lesion was recognized in 7 cases by the review of the initial radiographic films, and all of them were visualized as unilateral deformity (depressed sign) of various grades. It was not confirmed in the remaining 7 cases.

　Meticulous interpretation of radiographic films is required to avoid oversights, and the following points are considered to be of much importance to achieve this purpose. (1) The use of antispasmodics is mandatory, except in cases of contraindication, to minimize anxiety and tension of patients and obtain as well as optimal lumen distension. (2) Double contrast radiographs should be taken segmentally from the rectum to the proximal portion, and various positioning should be used for avoiding the overlapping of the loops. (3) Compression is recommended to make sure lesions are detected especially in the right and transverse colon, if possible. (4) A higher concentration of barium is to be used in cases in which, for various reasons, sufficient preparation of the patient may not have been made.