Value of Computerized Tomography Enterography in Predicting Crohn's Disease Activity: Correlation with Crohn's Disease Activity Index and C-Reactive Protein

Abstract

Background: The accurate evaluation of Crohn's disease activity is important for the treatment of the disease and for monitoring the response. Computerized tomography (CT) enterography is a useful imaging modality that reflects enteric inflammation, as well as extramural complications.

Objectives: The aim of this study was to evaluate the correlation between CT enterographic (CTE) findings of active Crohn's disease and the Crohn's disease activity index (CDAI) and C-reactive protein (CRP).

Patients and methods: Fifty CT enterographies of 39 patients with Crohn's disease in the small bowel were used in our study. The CDAI was assessed through clinical and laboratory variables. Multiple CT parameters, including mural hyperenhancement, mural thickness, mural stratification, comb sign, and mesenteric fat attenuation, were evaluated with a four-point scale. The presence or absence of enhanced lymph nodes, fibrofatty proliferation, sinus or fistula, abscess, and stricture were also assessed. Two gastrointestinal radiologists independently reviewed all CT images, and inter-observer agreement was examined. Correlations between CT findings, CRP, and CDAI were assessed using Spearman's rank correlation and logistic regression analysis. To assess the predictive accuracy of the model, a receiver-operating characteristic curve analysis for the sum of CT enterographic scores was used.

Results: Mural hyperenhancement, mural thickness, comb sign, mesenteric fat density, and fibrofatty proliferation were significantly correlated with CDAI and CRP (P < 0.05). The binary logistic regression model demonstrated that mesenteric fat density, mural stratification, and the presence of enhanced lymph nodes (P < 0.05) had an influence on CDAI severity. The area under the receiver operating characteristic curve (AUROC) of the CTE index for predicting disease activity was 0.85. Using a cut-off value of 8, the sensitivity and negative predictive values were 95% and 94%, respectively.

Conclusion: Most CTE findings correlated with CDAI and CRP in patients with active Crohn's disease.

Keywords: CRP; CT Enterography; Crohn’s Disease; Crohn’s Disease Activity Index; Small Intestine.

Figure 1.. Five CTE Parameters. A, Mural hyperenhancement, defined as segmental increased attenuation of the bowel wall (arrow) compared with the attenuation of normal small bowel loop (asterisk); B, Mural thickness, defined as a bowel wall thickness of > 3 mm (arrows); C, Mural stratification, defined as a visualization of a two- or three-layer appearance within the bowel wall (arrows); D, Increased density in the mesenteric fat (arrows); E, and F, The comb sign, defined as vascular enlargement of the vasa recta (arrows).

Figure 2.. A, Transverse; B, Coronal CTE images of a 21-year-old woman with the highest CTE index (score of 15) among the 23 patients, showing abnormal bowel enhancement with wall thickening (white arrows) in the terminal and distal ileum, mural hyperenhancement (double arrows), and fistula formation (arrow heads) between the distal ileal loops (CDAI = 197.5, CRP = 67.3 mg/dL).

Figure 3.. Coronal CTE image of a 35-year-old woman with the lowest CTE index (score of 3), showing only slight mural enhancement with mild bowel wall thickening in the terminal ileum (arrow). In this patient, the CDAI score was also low at 70.6, and CRP was 0.5 mg/dL

Figure 4.. A, Transverse; B Coronal CTE images of a 32-year-old man with a low CTE index (score of 7), which is lower than the given cut-off value, showing mural hyperenhancement with mild thickening (arrows). This patient’s CDAI score was 157, indicating active Crohn’s disease, and his CRP was 6.4 mg/dL