Diagnosis of necrotic and non-necrotic small bowel strangulation: The importance of intestinal congestion

Abstract

Background: Despite the prevalence of laparoscopic techniques in abdominal surgeries today, bowel obstruction remains a potentially serious complication. Small bowel strangulation (SBS), in particular, is a critical condition that can lead to patient mortality. However, the prognosis for SBS is favorable if surgery is performed before the onset of necrosis. Non-necrotic SBS is a reversible condition in which blood flow can be restored by relieving the strangulation. The purpose of this study was to identify sensitive and specific contrast-enhanced computed tomography (CT) findings that are useful for diagnosis of both non-necrotic and necrotic SBS.

Methods: We included patients diagnosed with SBS and simple bowel obstruction (SBO) who underwent contrast-enhanced CT followed by surgery from 2006 to 2023. Two gastrointestinal surgeons independently assessed the images retrospectively.

Results: Eighty SBO and 141 SBS patients were included. Eighty-seven had non-necrotic SBS and 54 had necrotic SBS. Mesenteric edema was most frequently observed in both necrotic and non-necrotic SBS cases followed by abnormal bowel wall thickening. These two findings were observed significantly less frequently in SBO. Bowel hypo-enhancement is identified in only about half of the non-necrotic SBS cases, and it was detected at significantly higher rates in necrotic SBS compared to non-necrotic.

Conclusion: Mesenteric edema and abnormal bowel wall thickening are sensitive and specific signs of both non-necrotic and necrotic SBS. These two findings indicate mesenteric and bowel congestion. Detecting intestinal congestion can lead to an accurate diagnosis of SBS, particularly in case of non-necrotic SBS, where bowel hypo-enhancement may sometimes be absent.

Keywords: acute abdomen; small bowel obstruction; strangulation.

FIGURE 1

Computed tomography (CT) findings. (A) The beak sign is characterized by tapering of the intestine, similar to a bird's beak. (B) The whirl sign refers to angiectopia of the mesenteric vessels and is U‐ or C‐shaped. (C) Abnormal bowel wall thickening is defined as thickening of >3 mm. (D) High density of the bowel wall on plain CT refers to high density on pre‐contrast CT due to hemorrhage and congestion. (E, F) Mesenteric edema refers to an increase in the mesenteric CT value. (G) The disappearance of Kerckring folds refers to a >10‐cm length of intestine without Kerckring folds. Patients with intestinal dilation of >5 cm and the disappearance of Kerckring folds with obvious bowel enhancement were excluded because this finding is caused by dilatation, not disturbance of blood flow. (H) Bowel hypo‐enhancement refers to a lack or attenuation of an enhancement effect of the bowel wall. This image is from the same patient depicted by Figure D; however, this image is from a contrast‐enhanced CT scan. Comparison with a plain CT clearly shows the lack of an enhancement effect.

FIGURE 2

Delayed enhancement effect. (A) Minimal or no enhancement effect is observed in the early contrast phase. (B) Enhancement effect is evident in the portal vein phase. We interpret this phenomenon as a delayed enhancement effect, attributed to impaired venous return, which is equivalent to a reduced enhancement effect.