Fecal calprotectin reflects endoscopic activity in patients with small-bowel Crohn's disease according to double-balloon endoscopy findings.

Fecal calprotectin (FC) has drawn attention as a biomarker in the evaluation of Crohn's disease (CD). However, few reports have provided a detailed examination of the relationship between small-bowel CD lesions and FC levels. The present study aimed to examine the entire small bowel using double-balloon endoscopy (DBE) and to determine the relationship between the endoscopic activity in small-bowel CD and FC levels. Twenty small-bowel CD patients, who underwent DBE, were prospectively enrolled. Endoscopic evaluation was based on the simple endoscopic score for CD, with the small bowel divided into four regions. This score was defined as the double-balloon endoscopic score for CD (DES-CD). Furthermore, to focus on mucosal membrane damage, we used the partial DES-CD (pDES-CD), in which presence of stenosis was excluded from DES-CD. DES-CD revealed a correlation with FC (γ = 0.691, P = 0.001) and C-reactive protein (CRP) (γ = 0.631, P = 0.003) levels. Furthermore, pDES-CD showed a correlation with the FC level (γ = 0.747, P < 0.001), erythrocyte sedimentation rate (γ = 0.492, P = 0.028), and the CRP level (γ = 0.605, P = 0.005). CD Activity Index and endoscopic score showed no correlation. Our results revealed a correlation between the endoscopic activity in small-bowel CD and FC levels. Furthermore, pDES-CD showed a strong correlation with FC levels. This may be because FC levels were elevated due to mucosal membrane damages, rather than stenoses.