For patients with closed-loop small bowel obstruction (CL-SBO), emerging research suggests that four key signs on computed tomography (CT), including increased attenuation of intestinal contents and the intestinal wall, may help predict bowel necrosis.
For the retrospective study, recently published in Radiology, researchers reviewed CT findings for 145 patients (median age of 62) who had closed-loop small bowel obstruction. Sixty-one patients in the cohort had bowel necrosis and the remaining 84 patients did not have bowel necrosis, according to the study.
In a multivariable analysis, the study authors found that increased attenuation of intestinal contents (difference value of > 8 HU) was over 45 times more likely in cases of bowel necrosis for patients with CL-SBO. Increased attenuation of intestinal contents also had an 81 percent area under the curve (AUC), a 99 percent specificity rate and a 98 percent positive predictive value (PPV) for predicting bowel necrosis in this patient population, according to the study authors. The researchers also noted 84 percent interobserver agreement for increased attenuation of intestinal contents.
“Therefore, we speculate that increased attenuation of intestinal contents is a valuable CT sign to predict bowel necrosis with high specificity and reproducibility,” wrote lead study author Bing-Qi Li, Ph.D., who is affiliated with the Department of General Surgery at Peking University Third Hospital in Beijing, China, and colleagues.
The researchers noted that increased attenuation of the intestinal wall (a difference value of >5.8 HU) was 15.1 times more likely in cases of bowel necrosis for patients with CL-SBO. While the study authors found a 92 percent specificity rate, a 79 percent AUC and an 85 percent PPV for increased attenuation of the intestinal wall in predicting bowel necrosis, they also noted 59 percent interobserver agreement.
“The bowel wall is a thin structure that precludes accurate density measurement because of the undersized area of the region of interest,” noted Li and colleagues. “The adjacent dilated small bowel and mesenteric effusions may hamper the recognition of the intestinal wall contour, and the subjective selection of the region of interest leads to great interobserver variability.”
Three Key Takeaways
- Increased attenuation of intestinal contents as a predictive CT sign. The study suggests that an increased attenuation of intestinal contents, with a difference value of > 8 HU, is a valuable CT sign for predicting bowel necrosis in patients with closed-loop small bowel obstruction (CL-SBO). This finding had a 99 percent specificity rate and a 98 percent positive predictive value (PPV), making it a highly specific and reproducible indicator of bowel necrosis.
- Increased attenuation of intestinal wall as a secondary predictor of bowel necrosis. Another noteworthy CT sign is the increased attenuation of the intestinal wall with a difference value of >5.8 HU. While this sign was found to be 15.1 times more likely in cases of bowel necrosis, the study authors acknowledged challenges in accurate density measurement due to the thin structure of the bowel wall. Despite a 92 percent specificity rate and an 85 percent PPV, there was lower interobserver agreement (59 percent) for this CT sign.
- Additional predictive factors. Beyond attenuation values, the study identifies two other independent predictive factors for bowel necrosis in CL-SBO patients: diffuse mesenteric haziness and the presence of mesenteric fluid on CT. Diffuse mesenteric haziness demonstrated a high specificity rate (93 percent) and PPV (85 percent) but had limitations in sensitivity (56 percent) and interobserver agreement (60 percent). Mesenteric fluid, while having a 75 percent negative predictive value and similar sensitivity (64 percent) as increased attenuation of intestinal contents, had the lowest interobserver agreement (48 percent) among the assessed CT signs.
Other independent predictive factors of bowel necrosis in patients with CL-SBO included diffuse mesenteric haziness and mesenteric fluid on CT, according to the study authors.
The researchers said diffuse mesenteric haziness demonstrated a 93 percent specificity rate and an 85 percent PPV, but they also acknowledged a 56 percent sensitivity rate and 60 percent interobserver agreement. Mesenteric fluid had a 75 percent negative predictive value and similar sensitivity (64 percent) as increased attenuation of intestinal contents, noted the study authors. However, they also pointed out that mesenteric fluid had the lowest interobserver agreement (48 percent) of the 10 CT signs assessed in the study.
(Editor’s note: For related content, see “Bowel Findings Revealed with Abdominal Imaging in COVID-19 Patients,” “CT Study Says Deep Learning Model Could Help Differentiate Between Acute Diverticulitis and Colon Carcinoma” and “Image IQ Quiz: Middle-Aged Female with Abdominal Pain.”)
Beyond the inherent limitations of a single-center retrospective study, the authors conceded possible patient selection bias due to the exclusion of patients with intestinal volvulus and those who had conservative treatment. They also acknowledged difficulty with accurate measurement of intestinal content attenuation in 12.4 percent of the cohort due to the lack of an obviously dilated loop.
