Bologna guidelines for diagnosis and management of adhesive small bowel obstruction (ASBO): 2017 update of the evidence-based guidelines from the world society of emergency surgery ASBO working group
ten Broek, R.P.G., Krielen, P., Di Saverio, S. et al. Bologna guidelines for diagnosis and management of adhesive small bowel obstruction (ASBO): 2017 update of the evidence-based guidelines from the world society of emergency surgery ASBO working group. World J Emerg Surg 13, 24 (2018). https://doi.org/10.1186/s13017-018-0185-2
Executive Summary
This briefing document synthesizes the 2017 updated Bologna guidelines from the World Society of Emergency Surgery (WSES) for the diagnosis and management of Adhesive Small Bowel Obstruction (ASBO). ASBO is a leading surgical emergency, responsible for 51% of all emergency laparotomies in the UK and accounting for a significant portion of general surgery morbidity, mortality, and healthcare expenditure in the USA. Post-operative adhesions are the primary cause in 60% of cases.
The core tenets of the guidelines emphasize a structured, evidence-based approach. Non-operative management is the initial treatment of choice for most patients, proving effective in 70-90% of cases. This conservative trial, involving bowel rest, decompression, and intravenous fluids, can be safely continued for up to 72 hours in the absence of signs of peritonitis, strangulation, or ischemia.
For diagnosis, computed tomography (CT) with oral water-soluble contrast is the preferred imaging modality. It accurately diagnoses small bowel obstruction, helps exclude other etiologies, and has approximately 90% accuracy in predicting the need for urgent surgery. Water-soluble contrast studies are also valuable for predicting the success of non-operative management.
Prevention is a critical theme, with recommendations to use minimally invasive surgical techniques and adhesion barriers. A hyaluronate carboxymethylcellulose barrier has been shown to reduce reoperations for ASBO in colorectal surgery. When surgery is required for ASBO, a laparoscopic approach may benefit carefully selected patients (e.g., those with a single adhesive band), but it carries a higher risk of bowel injury and requires significant expertise. Special consideration is given to patient groups such as the young, who have a high lifetime risk and may benefit most from prevention, and pregnant patients, in whom non-operative management has a very high failure rate.
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1. Epidemiology and Impact of ASBO
Adhesive small bowel obstruction is a significant public health issue, categorized as one of the leading causes of surgical emergencies.
Prevalence: Post-operative adhesions are the leading cause of small bowel obstructions, accounting for 60% of all cases. In the UK, SBO is the indication for 51% of all emergency laparotomies.
High-Risk Surgeries: The risk of SBO is highest following colorectal, oncologic gynecological, and pediatric surgery. One in ten patients develops an SBO episode within three years after a colectomy.
Morbidity and Mortality: ASBO is associated with considerable harm, with an average hospitalization of 8 days and an in-hospital mortality rate of 3% per episode.
Economic Burden: The need for surgical intervention dramatically increases costs. A 2016 Dutch study estimated the average cost of surgical treatment at €16,305, compared to €2,227 for non-operative management. Hospitalization length averages 16 days for surgical patients versus 5 days for non-operatively treated patients.
Recurrence Rates: Recurrence of ASBO is common.
Non-Operative Treatment: 12% of patients are readmitted within 1 year, rising to 20% after 5 years.
Operative Treatment: 8% of patients are readmitted within 1 year, and 16% after 5 years.
2. Definitions and Classification Systems
Key Definitions
Peritoneal Adhesions: Fibrous tissue that connects normally separated surfaces or organs within the peritoneal cavity. They result from a pathological healing response to peritoneal injury, most commonly from abdominal surgery.
Adhesive Small Bowel Obstruction (ASBO): A surgical emergency where the small intestine is blocked by adhesions, hindering the passage of intestinal contents. It is characterized by abdominal pain, vomiting, distention, and constipation.
Adhesiolysis: The surgical procedure of releasing adhesions via blunt or sharp dissection.
Complicated Adhesiolysis: An inadvertent injury occurring during adhesiolysis, most frequently to the bowel. Bowel injuries are classified as:
Seromuscular Injury: Injury to the serosa and smooth muscle layer without penetrating the lumen.
Enterotomy: A full-thickness injury where the lumen is visible or intestinal contents leak.
Delayed Diagnosed Perforation: A bowel injury that goes unrecognized during surgery.
Adhesion Classification Scores
Several scoring systems exist to classify adhesions, though all are limited to operative cases.
Risk Stratification Scores for Surgery
Models have been developed to predict the need for surgical intervention:
Zielinski Model: Uses three radiological and clinical signs (mesenteric edema, absence of small-bowel feces sign, obstipation) to predict the need for surgery with a concordance index of 0.77.
Baghdadi Model: A more complex but accurate model incorporating radiological findings, sepsis criteria, and comorbidity index. It demonstrated an area under the curve of 0.80 in a validation study.
3. Prevention of ASBO
The guidelines introduce a new focus on preventing adhesion formation.
Surgical Technique
Laparoscopy: Minimally invasive surgery is believed to reduce adhesion formation. A systematic review found a lower incidence of reoperation for ASBO after laparoscopic surgery (1.4%) compared to open surgery (3.8%), but the effect seems modest when correcting for the type and indication of surgery.
Minimizing Trauma: Other technical aspects are important:
Foreign Bodies: Avoid foreign body reactions from sources like starch-powdered gloves and certain meshes.
Energy Devices: Bipolar electrocautery and ultrasonic devices cause less peritoneal injury than monopolar electrocautery.
Antibiotics: Animal data suggest that systemic and intraperitoneal antibiotics, particularly metronidazole, may reduce adhesion formation in septic conditions.
Adhesion Barriers
Adhesion barriers are adjuvants that act as a physical spacer, separating injured peritoneal surfaces to allow healing without forming fibrinous attachments.
4. Diagnostic Approach to ASBO
A structured diagnostic approach is crucial to differentiate ASBO from other causes of obstruction and to assess the need for urgent surgery. Delayed diagnosis represents 70% of malpractice claims in this area.
Initial Evaluation
History and Physical Exam: Assess for previous surgeries, intermittent colicky pain, distention, vomiting, and constipation. Pitfalls include the presence of watery diarrhea in incomplete obstruction or the absence of prominent pain in the elderly. The physical exam has low sensitivity (48%) for detecting strangulation.
Laboratory Tests: A minimum workup includes a blood count, lactate, electrolytes, CRP, and BUN/creatinine. A CRP > 75 or WBC > 10,000/mm³ may indicate peritonitis, though with low sensitivity. Electrolyte correction and assessment of hydration status are critical.
Imaging Studies
Plain X-rays: Have limited value, with an overall sensitivity of approximately 70%. They cannot reliably detect early signs of strangulation or differentiate between causes of obstruction.
Water-Soluble Contrast Studies: These are highly useful. If contrast does not reach the colon on an X-ray taken 24 hours after administration, it is highly indicative of failed non-operative management. These studies accurately predict the need for surgery and have been shown to reduce hospital stay.
CT Scans: This is the preferred imaging technique. Helical CT has a high diagnostic accuracy (~90%) for predicting strangulation and the need for urgent surgery. It can differentiate between causes of obstruction by excluding non-adhesive etiologies. Signs of a closed loop, bowel ischemia, or free fluid suggest an immediate need for surgery.
Ultrasound and MRI: These can be useful in specific situations where radiation is undesirable (e.g., pregnancy) or CT is unavailable. In experienced hands, ultrasound can detect free fluid and assess hydration. MRI can provide more anatomical detail if needed.
5. Management of ASBO
Non-Operative Management (NOM)
NOM should be attempted in all patients unless there are clear signs of peritonitis, strangulation, or bowel ischemia.
Principles: The core components are nil per os (NPO), decompression via a naso-gastric (NGT) or long intestinal tube, and intravenous fluid/electrolyte resuscitation.
Efficacy: NOM is effective in approximately 70–90% of patients with ASBO.
Duration: A trial of NOM for a 72-hour period is considered safe and appropriate. Continuing beyond this point in patients with persistent high tube output but no other deterioration remains debatable. Delays in surgery beyond this window are associated with increased morbidity.
Tubes: While an older trial found no difference between NGT and long tubes, a more recent trial found a trilumen long tube more effective (10.4% failure rate vs. 53.3% with NGT). However, long tubes require endoscopic placement.
Operative Management
Surgery is required for patients who fail NOM or present with urgent indications.
Laparotomy: Historically the standard approach.
Laparoscopy: Has been introduced as a less invasive option with potential benefits like less adhesion reformation and shorter hospital stays. However, its use is associated with a higher risk of bowel injury (reported rates of 6.3% to 26.9%).
Patient Selection for Laparoscopy: Careful selection is critical. Predictors for a successful laparoscopic adhesiolysis include:
≤ 2 previous laparotomies
History of appendectomy as the index operation
Absence of a previous median laparotomy incision
Expectation of a single adhesive band
6. Special Patient Groups
Young Patients
Lifetime Risk: The risk of adhesion-related complications is lifelong. Younger patients, and especially pediatric patients, have the highest lifetime risk.
Pediatric Incidence: In one cohort, the incidence of ASBO after surgery at a pediatric age was 12.6% after a median follow-up of 14.7 years.
Prevention Benefit: This group stands to benefit the most from adhesion prevention strategies. A cohort study showed a hyaluronate carboxymethylcellulose barrier reduced ASBO in pediatric patients from 4.5% to 2.0%.
Elderly Patients
Decision Making: Quality of life and frailty are paramount considerations, as recovery may be prolonged.
Comorbidities: Treatment principles must account for comorbidities. A recent cohort study suggests patients with diabetes mellitus may require earlier surgical intervention, as delaying surgery more than 24 hours was associated with a significantly higher incidence of acute kidney injury (7.5%) and myocardial infarction (4.8%).
Pregnancy
Rarity and Risk: SBO in pregnancy is very rare but presents a major clinical challenge with a significant risk of fetal loss (17% in one review) and a 2% risk of maternal death.
High NOM Failure: Non-operative treatment has an extremely high failure rate in pregnant patients with ASBO (94% in a literature review of 17 cases).
Imaging: Ultrasound and MRI are preferred imaging modalities to avoid radiation.
7. Summary of Conclusions and Recommendations
The following table summarizes the key conclusions from the 2017 WSES ASBO guidelines, graded by level of evidence.
