Evidence-based, cost-effective management of small bowel obstruction: An algorithm of the Journal of Trauma and Acute Care Surgery emergency general surgery algorithms work group

This algorithm was developed by the Journal of Trauma and Acute Care Surgery emergency general surgery algorithms work group to provide an evidence-based, practical approach to the initial evaluation and management of small bowel obstruction (SBO) in adults presenting in the emergency setting.1 The algorithm (Fig. 1) is intended to serve as a bedside reference for clinicians. It is annotated with letters linked to corresponding text that provides the rationale and references to support these recommendations. The algorithm is not a substitute for the clinical judgment and experience of bedside clinicians and should not be considered the "standard of care." We encourage institutions to use these recommendations to formulate local clinical protocols, recognizing that patient-specific factors and institutional factors may necessitate deviations from this algorithm.Figure 1: Management algorithm for management of SBO.Small bowel obstruction is a common reason for emergency general surgical consultation. The most common etiologies of SBO are adhesions from prior surgery, followed by abdominal wall hernias and other causes (bezoars, intussusception, tumors, inflammatory processes). Adhesive SBO is one of the most common complications following open and minimally invasive surgery, with an overall estimated lifetime risk of 2% to 3% following any abdominal procedure,2,3 increasing up to 10% following pelvic and colorectal procedures.4 As with many other emergency surgery diagnoses, there are competing issues in caring for patients with SBO. These include diagnosing the etiology of the SBO, identifying which patients require emergency surgery, and determining which patients will not resolve with nonoperative management before developing intestinal compromise or a prolonged preoperative stay. Further complicating the decision-making process in patients with SBO is the varied set of outcome parameters measured in many studies. It is well documented that patients with SBO who require bowel resection will have increased morbidity and mortality compared with patients who do not.5 While some patients will present with intestinal compromise upon admission, the goal in patients who fail nonoperative management is to intervene before the need for intestinal resection.6 Similarly, patients who fail nonoperative management and require surgery will have longer hospital length of stay (LOS) than their nonoperative counterparts.7 In this group, the time before surgery should be the outcome measure of importance. It is hoped that this algorithm will help clarify these points and assist bedside clinicians with the decision-making process in caring for this group of patients. INITIAL EVALUATION AND MANAGEMENT Patients with SBO will most commonly present with abdominal pain, nausea, vomiting, and abdominal distension. A careful history of the onset of pain and other symptoms should be elicited. Obstipation may not be present in early cases of SBO but should be part of the medical history. Previous surgery should be noted; however, as will be described later in this algorithm, the treatment of patients presenting with SBO, whether with or without prior surgery, is not different (section "Water Soluble Contrast Study"). Early in the onset of SBO, patients may experience crampy abdominal pain. This may eventually subside in the setting of complete obstruction and intestinal atony. In contrast, the sudden onset of constant severe pain may be the harbinger of intestinal ischemia and is always worrisome in the setting of SBO.8,9 The constellation of symptoms may also provide the clinician with an indication of the location of the obstruction, with nausea and vomiting typically associated with more proximal obstructions and abdominal distension often indicating more distal pathology. Abdominal examination may demonstrate tenderness, distension, and hyperactive or absent bowel sounds. The initial assessment should also include standard laboratory studies, as well as lactate and C-reactive protein levels. As abdominal wall hernias are the second most common etiology of SBO, careful examination of the groins (inguinal and femoral hernias) and the abdominal wall (spigelian, incisional, umbilical, and epigastric hernias) is of paramount importance. Patients with incarcerated hernias will commonly complain of discrete pain at the site of the hernia. In morbidly obese patients, it may be difficult to identify a small groin hernia as the etiology of SBO by physical examination alone. If a hernia is the etiology of the SBO, the clinician is referred to the Abdominal Wall Hernia Algorithm in this series.10 Imaging The current standard of care for patients with suspected SBO is an abdominal computed tomography (CT) scan with intravenous contrast. While not completely relegated to the "acute care surgical museum," the current role of plain abdominal films in the evaluation of the patient with SBO is limited. The accuracy of plain radiographs in diagnosing SBO ranges from 50% to 80%.11 More importantly, plain abdominal radiographs do not provide a clear etiology of the obstruction and are very poor at identifying closed-loop obstructions. Therefore, even when plain abdominal radiographs appear to establish a diagnosis of SBO, a CT scan is still necessary. Lastly, the interpretation of abdominal radiographs is more nuanced than CT, and as fewer abdominal radiographs are being ordered, there is a waning expertise in their evaluation. The role of ultrasound in diagnosing SBO continues to evolve with advancements in technology and clinicians' experience. A meta-analysis of 11 studies involving 1,178 patients found ultrasound to be 92% sensitive and 97% specific in diagnosing SBO.12 These excellent results likely reflect publication bias. Furthermore, like plain radiography, the mere diagnosis of SBO is insufficient to further guide treatment, making abdominal CT scanning the diagnostic modality of choice. CT Imaging Findings The advantage of CT scanning in evaluating patients with SBO is that it can definitively guide treatment. More than merely diagnosing SBO, it can provide detailed information as to the etiology, as well as identifying the 85% to 90% of patients who require emergency surgery.13,14 In short, the routine use of abdominal CT scanning has transformed the management of SBO. In a systematic review and meta-analysis including 45 studies with 4,004 patients, the pooled sensitivity and specificity of CT for diagnosing SBO were 91% and 89%, respectively.15 More importantly, the pooled sensitivity and specificity for detecting ischemia were 82% and 92%, respectively. While not perfect, this increased accuracy is significantly improved over the era that relied solely on physical examination, laboratory values, and plain radiology.16 Computed tomography findings that predict the need for urgent surgery include mesenteric edema, peritoneal fluid, signs of closed-loop obstruction, lack of small bowel feces sign, and a lack of small bowel enhancement.13,14,17–19 As with all emergent abdominal diagnoses, the decision for surgical intervention is not made solely based on CT results but is supplemented by findings on physical examination and laboratory values. Signs of peritonitis, involuntary guarding, increased white blood cell count, and elevated lactate and C-reactive protein levels have also been used in various scoring schemas that help predict the need for emergency surgery. Transition points are often reported and described in the CT reports of patients with SBO. The true meaning and implication of these transition points have been debated. In retrospective studies, a greater percentage of patients with transition points are noted to fail nonoperative management than those without them.20 However, many patients with transition points are successfully treated without surgery and vice versa. The presence of a transition point has not been successfully integrated into the existing scoring systems designed to predict the need for surgery. As a CT scan is a "snapshot" in time, transition points may merely be peristalsis with an area of collapsed bowel rather than definitive evidence of complete obstruction. Taken together, the identification of a transition point should not be ignored, but in isolation, it is usually insufficient to indicate that emergency surgery is necessary. Emergency Operative Intervention Approximately 20% of patients presenting with SBO will require emergent surgery. This group presents with signs of peritonitis, hemodynamic instability, or CT findings suspicious for intestinal ischemia and/or closed-loop obstruction. Expeditious operation should be undertaken following an abbreviated period of fluid resuscitation and correction of electrolytes. These patients often require an open approach, but minimally invasive techniques can also be safe and effective. They may be advantageous in clearing the anterior abdominal wall of adhesions before laparotomy incision, even if the primary cause of the obstruction cannot be managed laparoscopically. The use of optical entry techniques off the midline enhances the utility of the minimally invasive approach. Water Soluble Contrast Study Patients without the need for emergency surgery should undergo a period of nonoperative management consisting of intravenous fluid and nasogastric decompression regardless of the etiology of the SBO. If the patient rapidly improves, as evidenced by the passage of flatus and stool, their diet can be advanced, and they can be discharged. It is important to remember that patients may have SBO but still evacuate preexisting colorectal contents. Patients with a nonadhesive etiology of their SBO will be managed based on the specific diagnosis (see section "Nonadhesive Small Bowel Obstruction"). Patients with adhesive SBO who do not rapidly resolve should undergo a water soluble contrast study (WSCS) using diatrizoate meglumine and diatrizoate sodium (most often termed "Gastrografin challenge"). This pathway has been advocated in the 2017 update of the guidelines from the World Society of Emergency Surgery, as well as in the Eastern Association for the Surgery of Trauma practice management guidelines.5,21 There continues to be debate regarding the optimal timing of the WSCS after a period of gastric tube decompression (e.g., ≤24 vs. 48 hours), the volume of contrast to be used, and what constitutes a failure. In general, a WSCS should be performed with 60 to 100 mL of Gastrografin through the nasogastric tube, which is then clamped. Abdominal x-rays should be taken at proscribed intervals (e.g., 6, 12, and 24 hours). Failure of the contrast to appear in the cecum by 24 hours is a "positive" test, and the patient will most likely require surgical intervention. The overall success rate of nonoperative management declines as the time from admission increases; thus, most data suggest that a WSCS should be performed before 72 hours of admission. There have been some suggestions in single-center studies and one meta-analysis that the WSCS, through its osmotic effect, can be therapeutic in relieving SBO and decreasing the percentage of patients who will require surgery.22 Two other meta-analyses found no therapeutic effect of WSCS.23,24 It is worth noting that both analyses identified bias in the underlying studies. A 2007 Cochrane review found a beneficial effect of WSCS in reducing hospital LOS but no impact on the need for surgery.25 In contrast, a prospective multicenter trial comparing WSCS with saline found that WSCS did not affect the need for surgery or hospital LOS.26 The lack of benefit may have been due to study design, as the WSCS was performed only 2 hours following the CT diagnosis of SBO. A more recent meta-analysis, which included only more current trials, also noted significant heterogeneity of the timing and conduct of the WSCS.27 This analysis also found that WSCS did not affect the need for surgery, morbidity, or mortality. They concluded that WSCS decreased hospital LOS, presumably by improving decision making in patients who ultimately fail nonoperative management and should be part of the management algorithm for SBO. The SnapSBO study demonstrated that adherence to the Bologna guidelines (which includes the use of WSCS) in the management of SBO had a shorter LOS and improved outcomes.28 Of note, this study also found that patients with improved compliance with the guidelines, who ultimately required surgery, had fewer complications, with no anastomotic leaks or infections. Similarly, a review of adhesive SBO patient outcomes pre- (n = 13,257; 2012 to 2016) and post-WSCS (n = 7,333; 2019–2023) using American College of Surgeons National Surgical Quality Improvement Program data reported that post-WSCS patients had reduced time to operating room and decreased hospital LOS (6 vs. 10.5 days), with an associated 44.7% reduction in the number of surgeries for SBO.29 We would therefore recommend that, in stable patients, a WSCS be performed early, between 6 and 24 hours after instituting nasogastric decompression. Past surgical dogma was that patients presenting with SBO and no prior abdominal surgery had a higher (almost universal) need for surgical intervention. The concern in this group was that the SBO was likely not due to adhesions and would not resolve without operative intervention. With the increased use of CT imaging, that dogma has been challenged and essentially refuted.30–32 A position paper by the World Society of Emergency Surgery, an Eastern Association for the Surgery of Trauma multicenter trial, and a recent systematic review all demonstrated that adhesions remain the most common cause of SBO in the "virgin abdomen" and that a nonoperative management strategy is both possible and successful. A word of caution was advised by Choi and colleagues33 in a systematic review and meta-analysis of 6 studies, including 442 patients. While adhesions remained the most common cause of SBO, malignant etiologies varied from 8% to 13%. Of concern was that most malignant etiologies were not suspected before surgical intervention. Failure of Nonoperative Management and the Role of Open Versus Minimally Invasive Surgery Although the data vary widely depending on the studies, a significant number of patients will fail nonoperative management and require surgical intervention to relieve their SBO. With the increased expertise of providers and improvements in instrumentation, a greater percentage of patients with SBO can be managed by minimally invasive techniques. A study from the American College of Surgeons National Surgical Quality Improvement Program identified a significant increase in the use of laparoscopy for SBO.34 The latest iteration of the World Society of Emergency Surgery guidelines for SBO acknowledges that a minimally invasive approach for patients with SBO may lead to improved outcomes.5 Those guidelines also highlight the importance of careful patient selection and sufficient surgical experience. Specifically, their recommendations identify candidate patients for laparoscopic surgery as having two or fewer previous laparotomies or those with a presumed single band as the etiology of the obstruction. A review of the literature on laparoscopy for SBO by Farinella et al.35 in 2009 included 30 predominantly small studies from around the world. The success of laparoscopic adhesiolysis ranged from 40% to 88% with conversion to open surgery ranging from 0% to 52%. The authors identified factors associated with successful laparoscopic surgery, as well as relative and absolute contraindications (Table 1). A recent cross-sectional study from the Netherlands found that the performance characteristics of the Farinella criteria were poor as measured by only minor differences in the conversion rate, enterotomy, and mortality between groups with low and higher Farinella scores.36 They conclude that the strict application of the Farinella criteria might withhold laparoscopic surgery from a large group of patients. A meta-analysis of laparoscopic versus open surgery, including 14 studies and 37,007 patients, showed no significant differences in postoperative mortality, iatrogenic bowel perforations, length of postoperative stay, postoperative complications, and early readmissions.37 In sensitivity analyses, laparoscopic surgery was favored over open lysis of adhesions in postoperative mortality, postoperative hospital LOS, time to flatus, and severe postoperative complications. Patient selection in these studies likely influenced the findings, with "sicker" patients being more likely to be treated by open surgery. A randomized open-label study (LASSO Trial) of open versus laparoscopic surgery included 100 patients in each arm and found that laparoscopic treatment shortened hospital LOS.38 There were no differences in complications. A limitation of this trial is that it only included patients who were thought to have a single band on preoperative CT scanning. Patients were also excluded if they had significant comorbidities, were pregnant, or had a preoperative LOS greater than 1 week. A recent scoping review included 43 studies; however, only 23 had specific inclusion and exclusion criteria.39 Nonetheless, these data suggest that, in selected patients, a laparoscopic approach is both feasible and safe and has several potential advantages over open surgery. The suggested limitations of laparoscopic surgery are similar to those contraindications initially suggested by Farinella et al.35 (Table 1). The data from a single-center prospective cohort study conducted from 2015 to 2019 highlight the use of emergency laparoscopic surgery in patients with SBO.40 Of the 299 patients studied, a laparoscopic approach was attempted in 76% with 52% being successful. Patients with successful laparoscopic surgery had decreased LOS and earlier return to oral feeding. Patients who required conversion to open surgery had similar outcomes to those who were treated by open surgery at the outset. This study found that the attempt and success rates for laparoscopy increased over the 5-year study period. At the time of the development of this algorithm, no series of robotically directed small bowel adhesiolysis was identified in PubMed. It remains unknown whether this approach will further improve the success rate of minimally invasive surgery to treat patients with SBO. Table 1 - Farinella35 Criteria for Laparscopic Adhesiolysis Positive Predictive Factors 2 or Less previous laparotomies ≤2 Nonmidline laparotomy incision Previous appendectomy as sole prior surgery Single band as mechanism of SBO Laparoscopic management within 24 h of symptoms No signs of peritonitis Absolute contraindications >4 cm of small bowel dilatation Peritonitis Severe comorbidities: cardiovascular, respiratory, and hemostatic disease Relative contraindications Greater than 2 previous laparotomies >2 Multiple areas of adherences Nonadhesive SBO The etiology of nonadhesive SBO includes tumors, bezoars, intussusception, Crohn's disease, and other inflammatory processes within the peritoneal cavity (e.g., diverticulitis). In patients with Crohn's and inflammatory processes, treatment of the underlying disease may resolve the SBO. While these patients may need surgical intervention for the underlying disease itself, either on an emergency or elective basis, the SBO may be resolved. Bezoars account for a small percentage of patients presenting with SBO. In most cases, the bezoars remain in the stomach, although some will migrate to or are formed de novo in the small intestine. Small bowel bezoars causing SBO most commonly require surgical intervention (laparoscopic or open). Tumors, specifically intrinsic small bowel tumors resulting in SBO, will require surgical intervention. In these patients, it is possible that a trial of nonoperative management can temporize their condition, allowing them to undergo surgery in a more elective manner. Malignant small bowel obstruction (MSBO) or what is colloquially called "carcinomatosis" is challenging, associated with dismal prognosis, and requires careful evaluation.41 Computed tomography imaging and WSCS can be beneficial in determining the extent and location of tumor obstruction, helping to inform treatment options. A pragmatic trial implemented within the National Cancer Trials Network compared surgery versus nonsurgical (somatostatin analogue, steroids, gastrostomy) management for MSBO and found no difference in the number of days alive and out of the hospital from study enrollment.42,43 Based on these results, the optimal management of MSBO should be personalized through shared patient decision making, considering the type of tumor and potential cancer-specific treatment options. Palliative care consultation in these patients can be invaluable. CONCLUSION In conclusion, the management of patients with SBO remains a common and sometimes challenging surgical emergency. Computed tomography scanning is the diagnostic modality of choice with the recognition that, like all imaging modalities, it is not perfect in detecting ischemic or compromised intestine. In patients with adhesive SBO who do not require emergency surgery, a trial of nonoperative management is warranted. In stable patients, a WSCS should be performed within 24 hours of instituting nasogastric decompression to identify which patients will not resolve without surgery. Minimally invasive surgery should be attempted in patients without absolute contraindications.