潰瘍性大腸炎の診断基準の問題点―潰瘍性大腸炎におけるskip lesionの臨床像とその意義

Clinical Features and Significance of “Skip Lesion” Appearing in Patients with Distal Ulcerative Colitis

要旨　潰瘍性大腸炎の診断基準の1つに“直腸からの病変の連続性”が挙げられているが，直腸炎型や左側大腸炎型の潰瘍性大腸炎患者において正常粘膜を介した口側粘膜に潰瘍性大腸炎の活動粘膜と考えられるskip lesionの所見を16/39（41％）と高頻度に認めた．粘液組織学化学的検討からも，これら潰瘍性大腸炎におけるskip lesionは前処置によるartifactや全大腸炎型の部位による治癒像の差を見ているものではなく，潰瘍性大腸炎の活動病変と考えられた．この潰瘍性大腸炎におけるskip lesionの意義については，skip lesionを有する例では有さない例に比べて有意に口側進展例が多く，有意に手術の危険性が高かった．今後は潰瘍性大腸炎の診断基準にskip lesionの存在を明記することが必要で，更なるskip lesion症例の集積，分析が必要と考えられた．

　Continuous disease extending from the rectum is one of the most important criterion for the diagnosis of ulcerative colitis (UC). Recent advances in colonoscopy have revealed that there are some patchy discontinuous diseased areas in the oral side distant from the continuous active site and known as a “skip lesion” in patients with distal UC. In the last 10 years, 125 cases of UC were diagnosed and treated in our hospital. Among those, 86 cases were entire colitis and 39 cases were left sided colitis (19 cases) and proctitis (20 cases). Total colonoscopy using the indigocarmine dye spray method was performed for all the cases and a lot of minute abnormal colonoscopic findings were detected in the oral side distant from the continuous active site. Patchy discontinuous “skip lesion” was observed in 16/39 cases (41%) in distal UC and typical colonoscopic findings of skip lesion were “small yellowish spots” and the typical histologic finding was “cryptitis”. In order to elucidate whether such “skip lesion” in UC is artifact or active disease of UC, we performed mucohistochemical examination of the biopsy specimens obtained from UC patients including those with skip lesions. In the normal colon, colonic glands preferentially had sulphomucin. By contrast, colonic glands in active UC preferentially had sialomucin. Sialomucin expression rate in “skip lesion” was similar to that in active UC and was significantly higher than in quiescent UC and normal mucosa, suggesting that skip lesion was mucohistochemically equivalent to the active area of UC. As for the clinical significance of the skip lesion in UC, the rate of disease extension (extending from distal UC through the entire colitis) and the need for surgical operation were significantly higher in patients with skip lesion than in the patients without skip lesion. Patchy discontinuous “skip lesion” is often detected in patients with distal UC and those patients should be treated carefully during the follow-up periods.