Small Bowel Obstruction—Who Needs an Operation? A Multivariate Prediction Model

Abstract

Background Proper management of small bowel obstruction (SBO) requires a methodology to prevent nontherapeutic laparotomy while minimizing the chance of overlooking strangulation obstruction causing intestinal ischemia. Our aim was to identify preoperative risk factors associated with strangulating SBO and to develop a model to predict the need for operative intervention in the presence of an SBO. Our hypothesis was that free intraperitoneal fluid on computed tomography (CT) is associated with the presence of bowel ischemia and need for exploration. Methods We reviewed 100 consecutive patients with SBO, all of whom had undergone CT that was reviewed by a radiologist blinded to outcome. The need for operative management was confirmed retrospectively by four surgeons based on operative findings and the patient’s clinical course. Results Patients were divided into two groups: group 1, who required operative management on retrospective review, and group 2 who did not. Four patients who were treated nonoperatively had ischemia or died of malignant SBO and were then included in group 1; two patients who had a nontherapeutic exploration were included in group 2. On univariate analysis, the need for exploration (n = 48) was associated (p < 0.05) with a history of malignancy (29% vs. 12%), vomiting (85% vs. 63%), and CT findings of either free intraperitoneal fluid (67% vs. 31%), mesenteric edema (67% vs. 37%), mesenteric vascular engorgement (85% vs. 67%), small bowel wall thickening (44% vs. 25%) or absence of the “small bowel feces sign” (so-called fecalization) (10% vs. 29%). Ischemia (n = 11) was associated (p < 0.05 each) with peritonitis (36% vs. 1%), free intraperitoneal fluid (82% vs. 44%), serum lactate concentration (2.7 ± 1.6 vs. 1.3 ± 0.6 mmol/l), mesenteric edema (91% vs. 46%), closed loop obstruction (27% vs. 2%), pneumatosis intestinalis (18% vs. 0%), and portal venous gas (18% vs. 0%). On multivariate analysis, free intraperitoneal fluid [odds ratio (OR) 3.80, 95% confidence interval (CI) 1.5–9.9], mesenteric edema (OR 3.59, 95% CI 1.3–9.6), lack of the “small bowel feces sign” (OR 0.19, 95% CI 0.05–0.68), and a history of vomiting (OR 4.67, 95% CI 1.5–14.4) were independent predictors of the need for operative exploration (p < 0.05 each). The combination of vomiting, no “small bowel feces sign,” free intraperitoneal fluid, and mesenteric edema had a sensitivity of 96%, and a positive predictive value of 90% (OR 16.4, 95% CI 3.6–75.4) for requiring exploration. Conclusion Clinical, laboratory, and radiographic factors should all be considered when making a decision about treatment of SBO. The four clinical features—intraperitoneal free fluid, mesenteric edema, lack of the “small bowel feces sign,” history of vomiting—are predictive of requiring operative intervention during the patient’s hospital stay and should be factored strongly into the decision-making algorithm for operative versus nonoperative treatment.

Computed tomography features associated with operative management for nonstrangulating small bowel obstruction

“…Our results suggest that a transition point represents a fixed rather than a transient point of intestinal obstruction un likely to resolve without operative intervention. Four studies 6,[8][9][10] to date have evaluated the clinical relevance of a transition point; however, only the study by Hwang and colleagues 8 supports the finding of an increased likelihood of operative management. All 4 of these studies were subject to less stringent inclusion/ exclusion criteria and may not represent the population of patients targeted in the present study.…”

“…5,6 That said, the small bowel feces sign was previously reported to occur more frequently in patients with moderate and highgrade SBO. 11 While further pro spective studies are required to clarify this discrepancy, modest interobserver agreement among reporting radi ologists, as demonstrated in this study, may limit the usefulness of the small bowel feces sign in guiding clin ical decision making.…”

“…Two studies have shown the small bowel feces sign to be predictive of nonoperative resolution of SBO. 5,6 However, there are conflicting reports on the association between other radiographic features, such as the presence of a transition point or ascites, and the need for surgical intervention. [5][6][7][8][9][10] Furthermore, it is cur rently unknown whether the aforementioned CT find ings are reliably interpreted by independent radiologists in the setting of nonstrangulating SBO.…”

“…5,6 However, there are conflicting reports on the association between other radiographic features, such as the presence of a transition point or ascites, and the need for surgical intervention. [5][6][7][8][9][10] Furthermore, it is cur rently unknown whether the aforementioned CT find ings are reliably interpreted by independent radiologists in the setting of nonstrangulating SBO. Ideally, radio graphic features with both good inter observer correla tion and a strong association with operative manage ment will enable the surgeon to monitor selected pa tients who warrant careful observation for the in creased likelihood of surgical intervention without progressing to intestinal strangulation.…”

Clinical variables related to small bowel obstruction: comparison of patients with and without Crohn’s disease

“…The role of CT has also been defined and could aid in decision to operate or not. 11,30 Multiple predictors for need to operate in non CD related SBO was published by Ziellinski et al 31 In this analysis, intraperitoneal fluid, mesenteric edema, lack of a small bowel feces sign and vomiting had a 96% sensitivity and 90% positive predictive value for need for surgery. However, in the case of CD, acute ischemia with free perforation is uncommon.…”