潰瘍性大腸炎の初期病変―画像所見の特徴と鑑別診断

Early Lesions of Ulcerative Colitis : Focused on Endoscopic Characteristics and Differential Diagnosis

要旨　潰瘍性大腸炎（UC）の初期病変の，内視鏡所見の特徴を明らかにすることを目的とした．当院で過去18年間に経験したUCの中で，2回以上大腸内視鏡による腸管病変の評価を行ったのは484例である．このうち，UCの初期病変と考えられる異常所見を認めた14例（2.9％）を対象とした．異常所見の発見時期は，UCの診断前が8例（初発群），UCの診断後で病変範囲の進展前が6例（進展群）であった．初発群の病変部位は直腸が多く，リンパ濾胞の過形成や，アフタ様や不整形のびらんを認めた．同部からの生検組織では，不均一な炎症所見やリンパ濾胞を認める頻度が高かった．一方進展群では，アフタ様や不整形のびらんを5例で認め高頻度であった．以上の結果から，UCの初期病変はリンパ濾胞の過形成や小型のびらんと考えられる．特に，こうした小病変を直腸に認める場合はUCの典型病変へ進展する可能性があり，大腸内視鏡による経過観察が必要である．

　The objective of this study was to clarify the endoscopic characteristics of early lesions of ulcerative colitis（UC）. Among patients with UC treated at our hospital during the past 18 years, colonic lesions were evaluated by colonoscopy two or more times in 484 patients. We studied 14（2.9％）of these patients who had abnormal findings considered to be early lesions of UC. Abnormal findings were detected before the diagnosis of UC in 8 patients（early disease group）and after the diagnosis of UC but before the proximal spread of lesions in 6 patients（progressive disease group）. In the early disease group, 6 patients had rectal lesions, associated with lymphoid follicular hyperplasia and aphthoid or irregularly shaped erosions. Histopathological examination of biopsy specimens obtained from affected areas showed that many patients had localized inflammation and lymphoid follicles. In the progressive disease group, 5 patients had aphthoid or irregularly shaped erosions. Our results suggested that early lesions of UC are characterized by lymphoid follicular hyperplasia and small erosions. In particular, such lesions arising in the rectum may progress to typical lesions of UC. Follow-up colonoscopic examinations are therefore essential.