─最近注目される腸管感染症─アメーバ性大腸炎

Amebic Colitis

要旨●アメーバ性大腸炎は比較的まれな消化管感染症であったが，最近では年間1,000例以上の発症が報告されている．2005年以降当院で生検および直接鏡検で虫体，栄養体が確認された35例（男性：33例，女性：2例），平均年齢47.5歳を解析しその特徴をまとめた．有症状者は63％，無症状者37％．推定される感染経路は，異性間感染49％，同性間感染9％，不明43％．生検陽性率は89％，直接鏡検陽性率は93％，血清アメーバ抗体陽性率は53％．好発部位は，盲腸89％，直腸51％であった．特徴的な内視鏡所見は，たこいぼ様びらん・潰瘍，不整形潰瘍，打ち抜き状潰瘍，類円形潰瘍，腫瘤形成様潰瘍などで，潰瘍の易出血性や膿汁流出様所見が特徴的である．診断は内視鏡所見で疑い，生検や直接鏡検，問診による背景の確認などが重要である．

　Amebic colitis is a relatively rare gastrointestinal infection, but its onset in ≧1,000 patients a year was recently reported. We analyzed 35 patients（33 men and 2 women ; average age, 47.5 years）who were diagnosed based on microscopic examination of the mucus obtained by biopsy using forceps and/or histological examination in our hospital. Among all patients included in the study, 63% were symptomatic and 37% were asymptomatic. The estimated route of infection was as follows：infection between sexes through commercial sex trade, 49% ; homosexuality, 8% ; and unknown, 43%. The diagnostic accuracy rate was 89% for histological examination, 93% for microscopic examination of mucus obtained by biopsy using forceps, and 53% for serum antibody value. The lesions were seen most commonly in the cecum（89%）and rectum（51%）. The distinctive findings of amebic colitis were as follows：raised erosion, irregular-shaped ulcer, punched-out ulcer, round-shaped ulcer, and tumorous ulcer ; these were seen with flowing mucous from ulcers and with friable. Diagnosis can be made by endoscopic findings, biopsy, and direct microscopy, and patient history confirmed via detailed interview is important.