Quantitative measurement and visual assessment of ileal Crohn's disease activity by computed tomography enterography: correlation with endoscopic severity and C reactive protein

Background: Few studies have correlated computed tomography (CT) enterography findings with endoscopic severity and C reactive protein (CRP) concentrations. Aim: To examine whether small bowel inflammation at CT enterography correlates with endoscopic severity and CRP in patients with Crohn's disease (CD). Methods: CT enterography datasets from 143 CD patients undergoing ileoscopy were examined for three different CT parameters: CT bowel enhancement, as defined by the ratio of terminal ileal versus control ileal loop attenuation; vascular enlargement of the vasa recta ("the comb sign''); and mesenteric fat density. Correlations between CT scan parameters, endoscopy, and histology severity scores, and CRP were assessed using Spearman's rank correlation and logistic regression. Results: Endoscopic score was significantly correlated with CT bowel enhancement, comb sign, and fat density (Spearman correlation coefficients 0.33 - 0.39; p < 0.001). Correlations with histological inflammation were strongest for bowel enhancement (r = 0.34 - 0.38; p < 0.001). CRP was elevated in patients with increased fat density versus those with increased bowel enhancement only (median 0.96 v 0.23, p = 0.002). CRP did not differ significantly between patients without evidence of active Crohn's and those with bowel enhancement and endoscopic inflammation not involving the perienteric tissues by CT (median 0.24 v 0.36; p = 0.38). Conclusion: Quantitative measures of bowel enhancement at CT enterography correlate with endoscopic and histological severity. CRP correlates with radiological findings of perienteric inflammation (increased fat density), but not of inflammation limited to the small bowel wall, underscoring the potential role of perienteric inflammation in CRP response in CD.