[Comparative study of CT relative enhancement value and subjective visual evaluation for intestinal ischemia in patients with closed loop obstruction].

To compare and evaluate the diagnostic performance of visual evaluation and CT maximal density relative enhancement value in the diagnosis of intestinal ischemia complication in patients with closed loop obstruction and to explore the feasibility of CT maximal density relative enhancement value in quantifying the degrees of intestinal ischemia. The clinical and CT imaging data of 82 patients, 46 males and 36 females, aged from 19 to 78(52±18) years, with closed loop obstruction were retrospectively analyzed in the First Affiliated Hospital of Zhengzhou University from July 2017 to July 2019. All patients were classified into three groups: necrosis group (28 cases), ischemia group (22 cases), non-ischemia group(32 cases) using clinicopathologic results as reference standard. CT visual evaluation was performed by two experienced radiologists. The sensitivity, specificity, positive and negative predictive values and accuracy of the two observers were calculated respectively. The inter-observer agreement was analyzed by kappa analysis. Maximal density relative enhancement value was defined as the difference CT value of an ROI at dilated obstructed loops between contrast-enhanced and unenhanced CT images. The differences among groups were compared by one-way analysis of variance. Diagnostic performances were evaluated by receiver operating characteristic (ROC) curve analysis. The sensitivity, specificity, positive and negative predictive values and accuracy of observer1 were 62.0%, 87.5%, 88.6%, 59.6%, 72.0%, and 58.0%, 93.8%, 93.5%, 58.8%, 72.0%for observer2, respectively. The kappa value of inter-observer agreement was 0.747. The unenhanced CT value of necrosis group, ischemia group and non-ischemia group was (53.7±9.7), (45.7±7.2) and (44.7±7.0) HU, enhanced CT value was (60.5±10.1), (65.0±11.6) and (87.0±15.8) HU, relative enhancement value was(6.8±8.4), (19.2±12.4) and(44.7±16.2)HU, respectively. All had a statistical difference among three groups (all <0.05). The unenhanced CT value of necrosis group was higher than that of ischemia group and un-ischemia group (both <0.05). The enhanced CT value of non-ischemia group was higher than that of ischemia group and necrosis (both <0.05). The relative enhancement value all had a significant difference between groups (all <0.05). Taking maximal density relative enhancement value below 19.5 HU as diagnosis threshold, the sensitivity, specificity and area under curve(AUC) were 96.9%, 74.0% and 0.947, respectively. Taking enhanced CT value below 66.5 HU as diagnosis threshold, the sensitivity, specificity and AUC were 93.8%, 60.0% and 0.903, respectively; the sensitivity was higher than that of objective visual evaluation. Maximal density relative enhancement value can quantize the bowel wall enhancement, and is a more reliable way in the diagnosis of intestinal ischemia than visual evaluation.