虚血性大腸炎および抗生剤起因性大腸炎と生検

Pathological Diagnosis of Ischemic Colitis (IC) and Antibiotic Associated Colitis (AAC)

要旨　虚血性大腸炎（IC）54例と，抗生剤起因性大腸炎（AAC）40例について，生検診断能と生権組織の経時的変化について検討した．発症3日以内の生検で，31例中26例（84％）がICと診断できた．しかし，日数の経過と共に生検診断率は低下し，8日以上経過した13例では，1例しか組織診断できなかった．ICは急性粘膜病変であり，生検材料が粘膜下層を含まなくても約80％が病理組織学的に診断された．再生上皮が出現した生検標本ではICの病理組織像を保持したものは少なかった．AACの病理組織像はICに類似しているが，一般に炎症の程度が歩く，散在性発赤だけを認めた4例では生検診断できず，発症3日以内の生検群16例中9例（56％）がAACと診断されたにすぎなかった．

　IC was pathologically diagnosed in 26 (84%) out of 31 cases in which biopsy specimens were taken within three days after the onset of symptoms. In contrast, IC was dianosed in four (40%) out of ten cases when biopsy was done between four and seven days after the onset and in only one (8%) out of 13 cases with biopsy done eight days or after.

　Among 31cases with biopsy done in the first three days, submucosal layer was contained in ten cases leaving 21 cases without submucosal layer. IC was pathologically diagnosed in nine cases among the former group and 17 among the latter. These data demonstrate that the earlier the biopsy specimen is obtained the better chance we have in diagnosing IC and that the biopsy specimen does not necessarily have to contain submucosal layer to be useful in the diagnosis.

　Pseudomembranous colitis type (PMC) of AAC were easy to pathologically diagnose if the pseudomembrane was picked up sufficiently.

　Non-PMC (acute hemorrhagic colitis: AHC), however, was not so easy to diagnose from biopsy specimen as in IC. Out of 16 cases of AHC only nine were pathologically diagnosed when biopsy specimens were obtained within three days after the onset.

　Thus, it seems that the histopathological appearance of some of AHC is too subtle to be recognized as abnormal.

　Histopathological difference between IC and AHC is merely the one in severity. There seem to be many aspects common to these two disease entities, which remain to be investigated.