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Adhesive small bowel obstruction (SBO) remains one of the leading causes of emergency room visits and is still associated with high morbidity and mortality rates. Because the management of adhesive SBO has shifted from immediate surgery to nonoperative treatment in the absence of ischemia, it is crucial to rapidly detect or predict strangulation, which requires emergent surgery. CT is now established as the best imaging technique for the initial assessment of patients suspected of having adhesive SBO. CT helps confirm the diagnosis of mechanical SBO, locate the site of obstruction, establish the cause, and detect complications. This article is a review of the role of imaging in answering specific questions to help predict the management needs of each individual patient. It includes (a) an update on the best CT signs for predicting ischemia and a need for bowel resection; (b) a discussion of the CT features that help differentiate open-loop from closed-loop obstruction and a single adhesive band from matted adhesions and how these differences can influence the management; and (c) a review of the main CT predictors of the success or failure of nonoperative management in adhesive SBO., (© RSNA, 2020.)

Large bowel obstruction (LBO) is associated with high morbidity and mortality due to delayed diagnosis and/or treatment. MDCT has become the standard of care to identify the site, severity, and etiology of obstruction. The goal of this review is fourfold. The first objective is to give clues to differentiate LBO from colonic pseudo-obstruction. The second objective is to describe CT features in the most common cause of LBO which is colonic cancer by illustrating classical and atypical features of colonic cancer responsible for LBO and by giving the features which must be reported when differentiating malignant from benign: presence of local lymph nodes, other colic localizations, length of involved segment, presence of diverticula, or other. The third objective is to illustrate the various causes of LBO which can mimic a colon cancer by leading to a thickening of the colonic wall: diverticulitis, ischemic colitis, endometriosis, inflammatory disease and to give tips which permit to evoke another diagnosis than a colon cancer in patient with a LBO and a thickening of the colic wall. The fourth objective is to describe the common signs of cecal and sigmoid volvulus and to give tips for a diagnosis sometimes difficult particularly for cecal volvulus: one of two transition points according to the type of volvulus and the presence of a whirl sign with a torsion of the mesenteric vessels., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Purpose: To identify computed tomography (CT) findings associated with successful conservative treatment of closed loop small bowel obstruction (CL-SBO) due to adhesions or internal herniation., Material and Methods: The local institutional review board approved this study while waiving informed consent. Clinical and CT data were collected retrospectively for 96 consecutive patients with a CT diagnosis of CL-SBO due to adhesions or internal herniation established by experienced radiologists who had no role in patient management. Mechanical obstruction with at least two transition zones on the bowel at a single site defined CL-SBO. Two radiologists blinded to patient data independently performed a retrospective review of the CT scans. The patient groups with successful versus failed initial conservative therapy were compared. Univariate and multivariate analyses were performed to look for CT findings associated with successful conservative therapy. Interobserver agreement was assessed for each CT finding., Results: Of the 96 patients, 34 (35%) underwent immediate surgery and 62 (65%) received first-line conservative treatment, which succeeded in 19 (31%) and failed in 43 (69%). The distance between the transition zones was the only independent predictor of successful conservative therapy (odds ratio, 4.6 when ≥ 8 mm; 95% confidence interval [95% CI], 1.2-18.3). A distance ≥ 8 mm had 84% (95% CI, 60-97) sensitivity and 46% (95% CI, 31-62) specificity for successful conservative treatment. The correlation coefficient for the distance between transition zones between readers 1 and 2 was fair (r = 0.46)., Conclusion: CL-SBO can be resolved without surgery. When there is no CT sign of ischemia, the distance between the transition zones should be assessed., Key Points: • Twenty percent (19/96) of all cases of closed loop small bowel obstruction (CL-SBO) representing 31% of the patients given first-line conservative therapy, were resolved without surgery. • The distance between the transition zones may help to choose between conservative and surgical management in patients with a CL-SBO but no CT evidence of ischemia. • A distance < 8 mm between the transition zones suggests a need for emergent surgery.

Objectives: To identify computed tomography (CT) findings associated with bowel necrosis in patients with surgically confirmed strangulating closed-loop small-bowel obstruction (CL-SBO) due to adhesions or internal hernia., Methods: This retrospective study was approved by our institutional review board, and informed consent was waived. To identify CT signs of bowel necrosis, two gastrointestinal radiologists performed blinded, independent, retrospective reviews of 41 CT studies from consecutive patients who had CL-SBO due to adhesions or internal hernias and who underwent surgery within 48 h. On the basis of surgical and pathological findings, patients were classified as having reversible ischemia or histologically documented necrosis. Univariate statistical analyses were performed to assess associations between CT signs and bowel necrosis. Kappa statistics were computed to assess interobserver agreement., Results: We included 25 (61%) women and 16 (39%) men with a median age of 79 years. Bowel necrosis was found in 25/41 (61%) patients and ischemic but viable bowel in 16/41 (39%) patients. Increased unenhanced bowel-wall attenuation was the only CT finding significantly associated with bowel necrosis (p = 0.0002). This sign had 58% (95% CI, 37-78) sensitivity and 100% (95% CI, 79-100) specificity for necrosis. Interobserver agreement was fair (0.59; 95% CI, 0.37-0.82)., Conclusion: Increased unenhanced bowel-wall attenuation is specific for bowel necrosis and should lead to prompt surgery for bowel resection., Key Points: • Increased unenhanced bowel-wall attenuation is the only sign specific for necrosis • Decreased bowel-wall enhancement is not relevant for differentiating reversible ischemia from necrosis • Preoperative knowledge of bowel necrosis is helpful to plan adequate surgery.

Objective: The objective of our study was to evaluate if the feces sign can be used to predict successful nonoperative treatment or progression to ischemia in patients with small-bowel obstruction (SBO) due to adhesions., Materials and Methods: For this single-center retrospective observational study involving a blinded independent review by two radiologists of 237 consecutive CT examinations of 216 patients with SBO due to adhesions (age: mean, 70.9 years; median, 74 years; interquartile range, 62-84 years), the location of the transition zone (TZ), number of TZs, and presence and location of the feces sign relative to the TZ were recorded. The reference standard for diagnosing ischemia was surgical and pathologic findings (n = 108 CT examinations) or, when treatment was nonoperative (n = 129 CT examinations), clinical outcome. Factors associated with successful nonoperative treatment and ischemia were identified by univariate and multivariate analyses., Results: A feces sign was seen in 88 of 237 CT examinations (37.1%). The feces sign was at the TZ, which we refer to as the "TZ feces" sign, in 82 of 88 (93.2%) patients; between two TZs, which we refer to as the "trapped feces" sign, in 14 (15.9%) patients; and in both locations in eight (9.1%) patients. By univariate analysis, an isolated TZ feces sign was associated positively with successful nonoperative treatment (odds ratio [OR], 3.37; 95% CI, 1.71-6.66; p < 0.001) and negatively with ischemia (OR, 0.33; 95% CI, 0.13-0.85; p = 0.02). Combined TZ and trapped feces signs were associated with ischemia (OR, 24.16; 95% CI, 2.86-203.89; p = 0.003). By multivariate analysis, regardless of the location of the feces sign, the feces sign was not significantly associated with successful nonoperative treatment or progression to ischemia., Conclusion: The feces sign is common and helps to identify the TZ. Among the CT signs of SBO, the feces sign does not independently help to predict successful nonoperative treatment or progression to ischemia.

Purpose To determine which computed tomography (CT) findings or combinations of findings can help to accurately identify strangulation in adhesive small bowel obstruction (SBO). Materials and Methods Contrast agent-enhanced CT findings in a cohort of 256 patients consecutively admitted for adhesive SBO, with a delay of less than 24 hours between CT and surgery for the operated patients, were reviewed independently by two radiologists, with consensus by a third, to assess CT findings commonly associated with strangulation. The reference standard for strangulation was surgery. Univariate and multivariate analyses were performed to identify predictors of strangulation in the entire cohort and to identify predictors of the need for surgical resection in the subgroup of patients with strangulation. A CT score was obtained and diagnostic performances of different combined CT findings were calculated. Results In this study, 105 patients (41.0%; 105 of 256) underwent a surgical procedure, 62 of whom were found to have strangulation (59.0%; 62 of 105), whereas 151 patients (59.0%; 151 of 256) improved with medical care. Three CT findings were significantly associated with strangulation in the multivariate analysis: reduced bowel wall enhancement (odds ratio, 7.8; 95% confidence interval [CI]: 2.6, 23.5), diffuse mesenteric haziness (odds ratio, 6.1; 95% CI: 2.5, 15.2), and a closed-loop mechanism (odds ratio, 6.5; 95% CI: 2.8, 15.5). The model combining these three features had an area under the curve of 0.91 (95% CI: 0.86, 0.96) and a high negative predictive value (97%; 95% CI: 93%, 99%). Positive likelihood ratios were high when two or three of these CT findings were combined (positive likelihood ratios, 14.7 [95% CI: 7.1, 30.4] and 43.8 (95% CI: 14.2, 135.2], respectively). Among the strangulated cases, reduced bowel wall enhancement (odds ratio, 3.9; 95% CI: 1.3, 12) and mesenteric fluid (odds ratio, 3.6; 95% CI: 1.0, 12.8) were predictive of resection. Conclusion A score that combines three CT findings (reduced bowel wall enhancement, a closed-loop mechanism, and diffuse mesenteric haziness) can accurately predict strangulation in adhesive SBO. © RSNA, 2017 Online supplemental material is available for this article.

Purpose To determine whether adding unenhanced computed tomography (CT) to contrast material-enhanced CT improves the diagnostic performance of decreased bowel wall enhancement as a sign of ischemia complicating mechanical small bowel obstruction (SBO). Materials and Methods This retrospective study was approved by the institutional review board, which waived the requirement for informed consent. Two gastrointestinal radiologists independently performed retrospective assessments of 164 unenhanced and contrast-enhanced CT studies from 158 consecutive patients (mean age, 71.2 years) with mechanical SBO. The reference standard was the intraoperative and/or histologic diagnosis (in 80 cases) or results from clinical follow-up in patients who did not undergo surgery (84 cases). Decreased bowel wall enhancement was evaluated with contrast-enhanced images then and both unenhanced and contrast-enhanced images 1 month later. Diagnostic performance of decreased bowel wall enhancement and confidence in the diagnosis were compared between the two readings by using McNemar and Wilcoxon signed rank tests. Interobserver agreement was assessed by using κ statistics and compared with bootstrapping. Results Ischemia was diagnosed in 41 of 164 (25%) episodes of SBO. For both observers, adding unenhanced images improved decreased bowel wall enhancement sensitivity (observer 1: 46.3% [19 of 41] vs 65.8% [27 of 41], P = .02; observer 2: 56.1% [23 of 41] vs 63.4% [26 of 41], P = .45), Youden index (from 0.41 to 0.58 for observer 1 and from 0.42 to 0.61 for observer 2), and confidence score (P < .001 for both). Specificity significantly increased for observer 2 (84.5% [104 of 123] vs 94.3% [116 of 123], P = .002), and interobserver agreement significantly increased, from moderate (κ = 0.48) to excellent (κ = 0.89; P < .0001). Conclusion Adding unenhanced CT to contrast-enhanced CT improved the sensitivity, diagnostic confidence, and interobserver agreement of the diagnosis of ischemia, a complication of mechanical SBO, on the basis of decreased bowel wall enhancement. (©) RSNA, 2016.

Purpose: To identify computed tomographic (CT) findings that are associated with the effectiveness of nonsurgical treatment in patients with adhesive small-bowel obstruction ( SBO small-bowel obstruction ) that was initially treated medically., Materials and Methods: The local institutional review board approved this retrospective study; the informed consent requirement was waived. Multi-detector row CT studies in 159 patients (64 women, 95 men; median age, 69 years) with adhesive SBO small-bowel obstruction that was initially treated medically were reviewed retrospectively and independently by two emergency radiologists to identify numerous CT findings that could be associated with the effectiveness of nonsurgical treatment. Results were compared according to the success or failure of nonsurgical treatment. Univariate statistical analyses were performed for qualitative and quantitative data, as appropriate, and each significant parameter was entered in a multivariate logistic regression analysis. The κ statistic and correlation coefficients were used to assess interobserver agreement, as appropriate., Results: Nonsurgical treatment succeeded in 113 patients (71%) and failed in 46 patients (29%). At univariate analysis, an anterior parietal adhesion, a feces sign, and the lack of a beak sign were associated with successful nonsurgical treatment, whereas two beak signs or more, a whirl sign, a C- or U-shaped appearance of the bowel loop, and a high degree of obstruction were associated with nonsurgical treatment failure. At multivariate analysis, fewer than two beak signs and the presence of an anterior parietal adhesion were independent predictors of the effectiveness of nonsurgical treatment, with odds ratios of 0.27 and 0.11, respectively., Conclusion: The number of beak signs and the location of the transition zone in relation to the anterior peritoneal layer are independent signs associated with the success or failure of nonsurgical treatment.

Management of mechanical occlusion, particularly of the small intestine, has altered considerably over recent years, with a change of paradigm and the indication for surgery depending on the cause of the occlusion and any signs of entrapment or strangulation. It is therefore important today to make a positive diagnosis of mechanical occlusion, to assess its degree, its location and its cause, and to look for signs of entrapment and strangulation. Only computer tomography can provide the answers to these different questions. The aim of this paper is to provide a reminder of the CT signs that enable us to confirm diagnosis of the various aspects of mechanical occlusion of the stomach and duodenum, small intestine or colon, to emphasize and illustrate the diagnostic traps in CT and to set out the key points of a CT report of mechanical occlusion., (Copyright © 2013 Éditions françaises de radiologie. Published by Elsevier Masson SAS. All rights reserved.)