直腸肛門部の炎症性疾患―粘膜脱症候群，cap polyposis

Mucosal Prolapse Syndrome and Cap Polyposis

要旨　粘膜脱症候群（MPS）とCP（cap polyposis）の臨床像，形態学的特徴について自験例を提示して概説した．MPSは排便時のいきみなど消化管粘膜の逸脱による慢性的機械的刺激や虚血性変化によって形成される病変の総称であり，直腸を中心に人工肛門近傍や憩室症に伴って発生することもある．MPSは肉眼的に隆起型，潰瘍型，平坦型に分類され，潰瘍型では歯状線からやや離れた部位に，隆起型では歯状線に接して発生することが多い．CPは半月ひだ上に広基性の隆起性病変が多発し，直腸からS状結腸を好発部位とする原因不明の疾患である．症状として粘液下痢を来し，血液検査で低蛋白血症を伴うことが多い．肉眼的，病理学的に隆起型MPSに類似点があり，広義のMPSに含まれるとする意見もあるが，症状，病変の分布，病理組織所見，治療を含めた臨床経過に相違点が少なからずあり，独立した疾患概念と考えられるようになってきた．

　This paper shows the clinical and morphologic characteristics of the MPS（mucosal prolapse syndrome）and CP（cap polyposis）. Chronic mechanical stimulation by abnormal colonic motility and mucosal ischemia are likely to have occurred at defecation in MPS leading to thickening and fibrosis of the colorectal wall, as well as colonic diverticula and the adjacent mucosa to artificial stoma. There are three types of MPS, protruded-, ulcerative- and flat-type in the classification. In the ulcerative type, the lesion is frequently distant from the anal verge, whereas it is adjacent to it in the protruded type. On the other hand, CP is a rare disorder, which has developed multiple broad-based elevated polypoid lesions on the apices of the semicircular fold in the rectum and sigmoid colon. However, the pathogenesis of CP remains uncertain. The symptoms such as mucous bloody stool and mucous diarrhea were noted more in CP than in MPS. In addition, CP, but not MPS, is associated with hypoproteinemia. There are a lot of common features between CP and protruded-type MPS. However, it is concluded that both are independent disease entities due to the differences in symptoms, distribution, histological findings and clinical courses including treatment.