ABSTRACT
Objective:To develop a mesenteric creeping fat index (MCFI) based on CT enterography (CTE) to characterize the degree of creeping fat wrapping around the inflamed gut in Crohn disease (CD), and to assess the relationship between MCFI and the inflammatory intestinal stricture.Methods:From December 2018 to July 2019, the patients with CD who underwent surgery in the First Affiliated Hospital of Sun Yat-Sen University were prospectively collected. The extent of perienteric mesenteric vessels wrapping around the gut was reconstructed to develop MCFI based on CTE images. The intestinal stricture index was obtained by calculating the ratio of the maximal upstream luminal diameter divided by the minimum luminal diameter apparent within the stricturing region. Using region-by-region correlation between CTE and surgical specimen, creeping fat score in intestinal specimen was obtained by assessing the extent of creeping fat wrapping around the resected bowel segment, and HE staining was performed on the bowel specimen corresponding to creeping fat to obtain the pathological inflammatory score. The Spearman correlation analysis was used to evaluate the correlation between MCFI, creeping fat score in intestinal specimen, and inflammatory score, intestinal stricture index. The ROC curve analysis was used to assess the accuracy of MCFI in distinguishing moderate-severe and mild inflammatory bowel walls.Results:Totally 30 CD patients were enrolled. The creeping fat score in intestinal specimen positively correlated with pathological inflammatory score ( r s=0.403, P=0.027) and with intestinal stricture index ( r s=0.642, P<0.001). MCFI positively correlated with creeping fat score in intestinal specimen ( r s=0.840, P<0.001), with pathological inflammatory score ( r s=0.497, P=0.005), and with intestinal stricture index ( r s=0.599, P<0.001). ROC analysis showed that the area under the curve of MCFI for differentiating moderate-severely from mildly inflammatory bowel walls was 0.718 (95%CI 0.522-0.913). Using MCFI≥4 as a cutoff value, the sensitivity and specificity were 81.8% and 47.4%, respectively. Conclusions:There was a correlation between creeping fat and inflammatory intestinal strictures in CD. MCFI can non-invasively depict the degree of creeping fat wrapping around the gut and assess the inflammatory intestinal stricture.
ABSTRACT
Objective:To explore the diagnostic efficacy of nomogram based on multi-parameter MRI for assessment of bowel fibrosis in patients with Crohn disease（CD).Methods:The clinical and imaging data of CD patients diagnosed by surgical histopathology in the First Affiliated Hospital of Sun Yat-sen University from June 2015 to March 2018 were prospectively collected. All the patients underwent conventional MRI and diffusion kurtosis imaging（DKI) within 2 weeks before surgery. Patients who underwent surgery between June 2015 and September 2017 were included in the model building group, and those who underwent surgery between October 2017 and March 2018 were included in the model validation group. We measured the apparent diffusion coefficient（ADC) from monoexponential model of diffusion-weighted imaging（DWI), apparent diffusional kurtosis（K app), and apparent diffusion for non-Gaussian distribution（D app) from non-Gaussian DKI model, and observed T 2WI signal intensity and enhancement pattern of the same segment. One to three intestinal specimens per patient were stained with Masson′s trichrome for the histological grading of fibrosis. Correlations between qualitative/quantitative MRI indexes and histological grades were evaluated using the Spearman rank test. Multivariate logistic regression analysis was performed to identify independent factors to be included into the nomogram for predicting the degree of bowel fibrosis and its diagnostic performance was assessed by internal and external validation. Results:A total of 40 CD patients were included, including 31 in the model construction group and 9 in the model verification group. A total of 81 intestinal specimens from 31 patients were graded as none-to-mild bowel fibrosis（ n=32) and moderate-to-severe bowel fibrosis（ n=49) according to a scoring system of fibrosis. In the training cohort, the K app value of moderate-to-severely fibrotic bowel walls was significantly higher than that of none-to-mildly fibrotic bowel walls, and the D appand ADC values of moderate-to-severely fibrotic bowel walls were significantly lower than those of none-to-mildly fibrotic bowel walls（ Z=-5.999, -4.521 and -3.893; P<0.001). There was no significant difference in T 2WI signal intensity or enhancement pattern between these two groups（χ2=1.571 and 0.103; P>0.05). Moderate and mild correlations of histological fibrosis grades with K appand D app( r=0.721 and -0.483; P<0.001), and a mild correlation with ADC（ r=-0.445, P<0.001) were found. Independent factors derived from multivariate logistic regression analysis to predict the degree of bowel fibrosis were K app and D app. Internal and external validation revealed good performance of the nomogram with concordance index of 0.901（95% confidence interval, 0.824-0.978) and 1.000, respectively, for differentiating none-to-mild from moderate-to-severe fibrosis. Conclusion:The DKI-based nomogram can be used to evaluate the bowel fibrosis in CD patients and provides a visual and simple prediction method for clinic.