特発性腸間膜静脈硬化症の病理からみた鑑別診断

Differential Diagnosis of Idiopathic Mesenteric Phlebosclerosis and Other Diseases Using Pathological Characteristics

要旨　特発性腸間膜静脈硬化症（idiopathic mesenteric phlebosclerosis;IMP）は，1993年に岩下らにより提唱された疾患である．IMPは比較的まれではあるが，今日では確立した疾患概念として広く受け入れられている．臨床的には高齢者の右側結腸優位にみられる病変で，その病理組織学的特徴は，①腸管膜側の小静脈と壁内枝に石灰化や骨化を伴う著明な線維性壁肥厚，②著明な粘膜下の線維化，③粘膜内の血管周囲の膠原線維沈着，④主に粘膜下層の小血管壁内の泡沫細胞（マクロファージ）の出現，⑤血管炎の所見はみられない，とされている．病理組織学的に，鑑別の対象となりうる疾患は，IMPの組織学的変化の基本である静脈の変化と膠原線維の間質への沈着がみられるもの，あるいはそれと類似した所見がみられるものであり，myointimal hyperplasia of mesenteric veins，enterocolic lymphocytic phlebitis，アミロイドーシス，collagenous colitisなどが挙げられる．これらの疾患の存在を認識し，その臨床病理学的特徴を十分理解しておくと鑑別診断は容易であると思われる．

　Idiopathic mesenteric phlebosclerosis（IMP）was firstly proposed by Iwashita et al. in 1993. IMP is relatively rare, however, it is now widely accepted as a disease entity. Clinically, the right-side colon of elderly patients is predominantly involved, and its characteristic histopathological features are as follows. ①Marked fibrous mural thickening with calcification of mesenteric veins and their branches, ②Marked submucosal fibrosis, ③The deposition of collagen around the vessels in the mucosa, ④The appearance of foamy macrophages within the walls of small vessels chiefly in the submucosa, ⑤Lack of vasculitis.

　Histopathologically, some diseases with venous degeneration, stromal collagen deposition and/or their mimicking features can be candidates for differential diagnosis. Examples are myointimal hyperplasia of the mesenteric vein, enterocolic lymphocytic phlebitis, amyloidosis and collagenous colitis. Differential diagnosis might be easier when these factors are recognized, if their histopathological featues are known.