The target sign: a significant CT sign for predicting small-bowel ischemia and necrosis

Abstract

Objective: To investigate the correlation between changes in the thickness and density of diseased small-bowel wall and small-bowel ischemia and necrosis (SBN) on CT imaging when small-bowel obstruction (SBO) occurs.

Methods: We retrospectively analyzed 186 patients with SBO in our hospital from March 2020 to June 2023. The patients were divided into simple SBO (control group) and SBN (case group) groups. We used logistic regression analysis, the chi-square test, and Fisher's exact test to analyze the correlation between the changes in the thickness and density of the diseased intestinal wall and the SBN. A receiver operating characteristic (ROC) curve was used to calculate the accuracy of the multivariate analysis.

Results: Of the 186 patients with SBO, 98 (52.7%) had simple SBO, 88 (47.3%) had SBN, and the rate of SBN was 47.3% (88/186). Multivariate regression analysis revealed that six CT findings were significantly correlated with SBN (p < 0.05), namely, thickening of the diseased intestinal wall with the target sign (OR = 21.615), thinning of the diseased intestinal wall (OR = 48.106), increase in the diseased intestinal wall density (OR = 13.696), mesenteric effusion (OR = 21.635), decrease in the diseased intestinal wall enhancement on enhanced scanning (OR = 41.662), and increase in the diseased intestinal wall enhancement on enhanced scanning (OR = 15.488). The AUC of the multivariate analysis reached 0.987 (95% CI 0.974-0.999). Specifically, the target sign was easily recognizable on CT images and was a significant CT finding for predicting SBN.

Conclusion: We identified 6 CT findings that were significantly associated with SBN, and may be helpful for clinical treatment.

Keywords: CT scanning; Ischemia and necrosis; Small-bowel obstruction.

Fig. 1

A 59-year-old female patient with adhesive SBO with SBN who underwent appendicitis surgery 2 years ago showed symptoms of abdominal pain and fatigue. a The dilated small-bowel indicates SBO, and mesenteric effusion can be seen (*). b Diffuse thickening and decreased density of the ileal wall with target signs (arrows) are observed, and the CT value of the small-bowel wall is measured to be approximately 15 HU. c After enhanced scanning, the thickening of the ileal wall with the target sign shows a decrease in enhancement (arrow), and the measured CT value of the small-bowel wall is approximately 17 HU, with almost no enhancement. d and e The CT images with coronal and sagittal reconstructions show a thickened ileal wall with the target sign (arrow). f In the image with 3D MPR (Three-dimensional multi-planar reformation), the target sign can be observed (arrow)

Fig. 2

A 46-year-old male patient with adhesive SBO with SBN had undergone appendicitis surgery more than 10 years ago, with symptoms of abdominal pain, nausea, vomiting, and fever. a Two thickened and high-density small-bowel walls with the target sign (arrows) can be seen on CT plain scanning, and the CT value of the small-bowel wall on plain scanning is approximately 53 HU. b The arrow shows the thickened small-bowel wall with a high-density target sign at different levels. c After enhanced scanning, the thickened small-bowel wall with a high-density target sign shows a decrease in enhancement. After enhancement, the CT value of the small-bowel wall is 57 HU, with almost no enhancement. d and e The coronal and sagittal views show a thickened small-bowel wall with the high-density target sign. f The target sign can be seen in the image with 3D MPR (arrow)

Fig. 3

A 65-year-old male patient with vascular SBO with symptoms of abdominal pain, vomiting, and fever. a The small-bowel is significantly dilated, accompanied by mesenteric effusion (*), indicating SBO. b Partial thinning of the jejunal wall indicates SBN (arrow). c After enhanced scanning, the enhancement of the thinner jejunal wall is reduced (arrow). d and e The coronal and sagittal views show a thinner jejunal wall with lower enhancement (arrow) and surrounding mesenteric effusion. f In the image with 3D MPR, the thinner small-bowel wall with surrounding mesenteric effusion indicates SBN (arrow). After communications and researchs with the surgeon, we had determined that the jejunal wall indicated by the arrow was the site of SBN

Fig. 4

A 66-year-old female patient with adhesive SBO and SBN underwent radical surgery for sigmoid colon cancer 4 years ago, with symptoms of abdominal pain and vomiting. After conservative treatment outside the hospital, small-bowel dilation was slightly alleviated, but symptoms such as abdominal pain did not show significant relief. a. Thickened small-bowel wall can be seen in the lower abdomen, presenting as an overall high-density target sign (arrows) on CT plain scanning, and the CT value of the diseased small-bowel wall is approximately 41 HU. b and c After enhanced scanning, the thickened small-bowel wall with a high-density target sign shows an increase in enhancement. After enhancement, the CT value of the small-bowel wall is 93 HU with significant enhancement, and the CT value of the diseased small-bowel wall increases by approximately 52HU. d and e The coronal and sagittal views show an thickened small-bowel wall with the overall high-density target sign (arrows). f The arrow indicates an overall high-density target sign with significant enhancement in 3D MPR

Fig. 5

The AUC under the ROC curve in the multivariate analysis was 0.987 (95% CI 0.974–0.999)