Strangulated obstruction is a life-threatening form of SBO. Hashimoto et al. reported the morbidity (31.3%) and mortality (5.4%) rate associated with SSBO . A prompt diagnosis of SSBO and surgical intervention are important for avoiding a serious outcome, such as perforation, sepsis, and death . A number of previous studies have evaluated the accurate and early diagnosis of SSBO, but early detection remains difficult; thus, the identification of more reliable diagnosis tools is urgently required. Identifying the preoperative predictive factors for bowel resection with SSBO is important. In the present study, we explored the factors predictive of the need for bowel resection due to SSBO using clinical parameters.
Significant predictive factors on a univariate analysis were the presence of a history of abdominal surgery, prolonged time from the onset of disease to the operation, increased CRP, decreased Alb, increased SOFA score, existence of closed-loop obstruction, and reduced enhancement of the intestinal wall at CT. However, we found in our regression analysis of multiple clinical variables that CT alone (specifically a reduced enhancement of the intestinal wall and the existence of closed-loop obstruction) was a moderately sensitive indicator of which patients with SSBO would require bowel resection.
In SBO, ischemia results from the concomitant effects or three factors: mechanical obstruction of the blood vessels due to twisting of the bowel loop; compression caused by distention of the obstructed loop, resulting in arterial and venous microcirculation blockage with anoxia; and venous congestion in the distended loop . Venous congestion can cause hemorrhagic venous infarction of the bowel wall , seen on CT as increased unenhanced bowel wall attenuation. However, this sign in not specific for bowel wall ischemia and can also be caused by bowel wall injuries, anticoagulant treatment, and bowel irradiation . Increased unenhanced bowel wall attenuation is difficult to quantify and has never been described in detail. This sign should be assessed subjectively by a comparison with the attenuation of the neighboring normal loops, which has been reported to range 10 to 20 HU .
A variety of CT signs, such as mesenteric fluid, mesenteric venous congestion free peritoneal fluid, and reduced bowel enhancement, have been reported as findings related to bowel strangulation [15–18]. Millet et al. reported that a reduced enhancement of the bowel wall is highly predictive of ischemia . Balthazar et al. reported that the detection of ischemic change in the bowel wall, attached mesentery, or both of on CT was diagnostic of bowel ischemia . Nakashima et al. reported that reduced enhancements of the bowel wall and mesenteric vessels was reliable for detecting bowel ischemia . Geffroyet al. reported that increased unenhanced bowel wall attenuation on 64-section multidetector CT had useful sensitivity and high specificity for the diagnosis of bowel wall ischemia in a highly select population of patients with surgically treated SBO .
Rondenet et al. reported that increased unenhanced bowel wall attenuation was the only significant predictor of necrosis in strangulated closed-loop SBO . In our study, a reduced enhancement of the intestinal wall and the existence of closed-loop obstruction were found to be independent predictive factors for bowel resection with SSBO.
Distinguishing bowel necrosis from non-necrosis with SSBO is pivotal for developing a well-considered preoperative strategy and planning urgent surgery . Preoperative knowledge of bowel necrosis is valuable for surgeons as they are thus better informed and better prepared for the possible need for bowel resection.
Several limitations associated with the present study warrant mention. First, this was a retrospective study and our data are based on the medical examinations performed at our hospital. Selection bias therefore could not be completely avoided. Second, due to the single-center setting, this model requires further validation. Further large-scale and well-designed studies are needed.