indeterminate colitisの臨床的検討―その定義と頻度，臨床経過について

Incidence and Clinical Course of Indeterminate Colitis

要旨　indeterminate colitis（以下，IND）は，通常，Crohn病（以下，CD）と潰瘍性大腸炎（以下，UC）の鑑別診断困難例とされる．今回，その定義，頻度，臨床経過について検討した．INDの定義は以下の3条件に合致する例とした．①UC or CD（狭義のIND）：初回診断時に，UCかCDかの確診が困難であった症例，②UC on CD：CDの経過中にUCの病像がoverlapする症例，③CD on UC：UCの経過中にCDの病像がoverlapする症例．この定義に該当する35例を対象とし，炎症性腸疾患（以下，IBD）患者に対する頻度，115.9±82.7か月の観察期間における臨床経過，特に，UC or CD 29症例の診断確定の有無および内容について解析した．当科における全IBD患者829例（CD 516例，UC 313例）に占めるINDの頻度は，4.2％（35/829）であった．UC or CD 29症例のうち，経過中に，確定診断した症例は23例（79.3％）で，最終診断の内訳は，CD 14例（60.9％），UC 9例（39.1％）だった．累積診断確定率は，3年で37.9％，5年で56.7％，8年で75.4％と算定された．最終診断UCの診断根拠は，典型的UCへ進展したものが6例（66.7％），切除標本の病理学的所見が2例（22.2％）であった．CDでは，granulomaの検出が4例（28.6％），典型的CDに進展したものが4例（28.6％），典型的な病変に進展し，かつgranulomaも認めたものが3例（21.4％），切除標本の病理学的所見が3例（21.4％），であった．本邦において，INDの定義は，いまだ明確ではない．しかし，今回の検討では，初回診断困難例も約80％は，経過中に確定診断に至っており，INDは，単一の疾患ではなく，一時的な仮の診断として位置づけることが妥当であると考えられた．

　[Aim] The aim of this study is to clarify incidence, clinical feature and clinical course of patients with indeterminate colitis (IND) in Japan. [Patients and Methods] We defined IND as follows ; ① Ulcerative colitis (UC) or Crohn's disease (CD) (IND in the narrow definition) : Patients whose definite diagnosis could not be determined to be either UC or CD by using diagnostic criteria (Japanese criteria) based on endoscopic, radiological and histological findings at the first diagnosis, ② UC on CD : Patients with definite CD whose UC-like presentation (diffuse colitis or diffuse proctitis) overlapped after the initial diagnosis, ③ CD on UC : Patients with definite UC whose CD-like presentation (upper GI lesion) overlapped after the initial diagnosis. Thirty-five patients (17 male, 18 female ; observation periods : 115.9±82.7 months) to whom this definition was applicable at our hospital were studied. Incidence in 29 patients with inflammatory bowel disease (IBD), clinical course, incidence of having definite diagnosis of UC or CD were analyzed. [Results] The incidence of IND among all IBD cases (n＝829, CD : 516. UC : 313) at our hospital was 4.2％ (35/829). In 29 patients with UC or CD, a definite diagnosis of either CD (n＝14, 54.1％) or UC (n＝9, 45.9％) was made during observation after the first diagnosis. The cumulative probability of having a definite diagnosis was 37.9％, 3 years after the initial diagnosis, 56.7％ at 5 years, 75.4％ at 8 years. As for 9 patients whose final diagnosis was UC, the reason for definite diagnosis in 6 (66.7％) was based on progress to typical UC and in 2 (22.2％) it was based on pathological findings of resected specimens. As for 14 patients whose final diagnosis was CD, the reason for definite diagnosis in 4 (28.6％) was based on the detection of granuloma, in 4 (28.6％) it was based on the progress to typical CD, in 3 (21.4％) it was based on both progress to typical CD and detection of granuloma and in 3 (21.4％) it was based on pathological findings of resected specimens. [Conclusion] In 29 patients clinical differential diagnosis could not be made either as CD or as UC at the first diagnosis, however, 23 of 29 (79.3％) patients had definite diagnosis during their clinical course. From these results, we concluded that IND was not a definitive entity but a temporary diagnosis and patients with IND at the first diagnosis need careful follow up for the final diagnosis.