小腸結核の診断─内視鏡所見の特徴と鑑別診断を中心に

Diagnosis of Small Bowel Tuberculosis-characteristics of Endoscopic Findings and Differential Diagnosis

要旨●当科で経験した回盲部以外の小腸に主病変を有する腸結核14症例を遡及的に検討した．診断時年齢は67.6±13.7歳と高齢で，性差は4：10と女性が多かった．ツベルクリン反応（ツ反）や抗原特異的インターフェロンγ遊離検査は施行されていたすべての症例で陽性であり，4例（28.6％）はツ反強陽性であった．内視鏡所見では多彩な形態と活動性の潰瘍が混在して認められる傾向にあった．活動性潰瘍は9例（64.3％）に認められ，4例（28.6％）は輪状潰瘍を呈し，輪状狭窄を4例（28.6％）に認めた．生検所見や各種の培養検査を加味しても内視鏡施行後の結核診断確定例は4例（28.6％）のみで，10例は疑診例であった．疑診例10例のうち6例は治療的診断がなされた．腸結核の診断確定は容易ではなく，Crohn病を代表とする他の炎症性腸疾患との鑑別が重要である．また，炎症性腸疾患患者では，抗TNF-α抗体が汎用されており，治療前の結核スクリーニングや潜在性結核感染への対処に十分な配慮が必要である．

　［Background］It is difficult to diagnose intestinal Tbc（tuberculosis）without a typical lesion in the ileocecal region. The diagnostic methods for and clinical course of this condition remain unclear.

　［Methods］We investigated the diagnostic methods including endoscopic findings, clinical course, and prognosis in subjects with intestinal Tbc without a typical lesion in the ileocecal region. There were 14 subjects（age：67.6±13.7 years, male：female＝4：10）diagnosed and treated at our hospital.

　［Results］TST（tuberculin skin test）and interferon-gamma release assay were positive in all subjects. Four subjects（28.6％）were strongly positive for the TST. Endoscopic findings tended to show various morphological lesions. An active ulcer was found in 9 subjects（64.3％）and an annular ulcer, which is a typical lesion of intestinal Tbc, and annular stenosis were found in 4 subjects each（28.6％）. Using the diagnostic criteria defined by Paustian et al., among the 14 subjects, only 4（28.6％）were diagnosed as having definite Tbc and 10 were diagnosed as having suspected Tbc. Among these 10 subjects without a definite diagnosis, 6 had improvement in small bowel lesions after the use of anti-Tbc drugs.

　［Conclusion and discussion］This study suggests that it is difficult to correctly diagnose intestinal Tbc involving only the small bowel. Recently, an anti-TNF-α antibody, which is a risk factor for Tbc infection and latent Tbc exacerbation, has been widely used for treating CD（Crohn's disease）. As both CD and intestinal Tbc often have small bowel lesions, morphological findings are very important for correctly diagnosing these diseases. Considering the risk of the incorrect use of the anti-TNF-α antibody for treating intestinal Tbc, it is necessary to make a strict differential diagnosis between these diseases using a morphological evaluation and proper screening for Tbc.