消化管―クローン病の診断

Gastrointestinal tract：diagnosis of Crohn’s disease

クローン病は主に若年者に発症し，小腸・大腸を中心に潰瘍，腸管狭窄や瘻孔を生じる，原因不明の肉芽腫性炎症性疾患である。クローン病の診断基準は，内視鏡所見，病理所見が主要所見であり，CT，MRIは診断時の参考という位置づけである。しかしながら，CT，MRI所見が診断における鍵となることも少なくない。本稿では，クローン病の診断についての基本的な知識と，診断の決め手になった画像・所見について初発例を提示しながら解説する。

In this article, we showed a review of the diagnostic criteria for Crohn’s disease（CD）in Japan and presented cases of three patients with newly diagnosed CD, focusing on the diagnostic roles of magnetic resonance enterography（MRE）.

The major and minor findings of the diagnostic criteria consist of endoscopic findings and a histological finding. Patients are classified into definite or suspected cases by using combinations of these findings. MRE are not included in these criteria.

In the case presentations, we demonstrated patients suspected of having small bowel CD. Two patients were diagnosed as definite cases of CD according to the diagnostic criteria, whereas the other patient was determined as a suspected case. This patient was treated with medical therapy of CD because MRE showed small bowel segments severely inflamed and the findings were pathognomonic：wall thickening, multiple stenosis, asymmetric involvement and segmental mural hyperenhancement. ‘Asymmetric’ is known as a specific finding for CD.

In conclusion, it is important to assess the disease extent and activity of the small bowel by using MRE in patients with suspected CD；MRE might be helpful to diagnose CD when pathognomonic findings of CD are detected in cases in which endoscopic findings are not definitive.