What is the management of non-adhesive Small Bowel Obstruction (SBO)?

Non-Adhesive Small Bowel Obstruction: Definition and Management

Non-adhesive small bowel obstruction (SBO) refers to mechanical obstruction of the small intestine caused by etiologies OTHER than peritoneal adhesions, most commonly including incarcerated hernias, malignant tumors (primary or metastatic), benign obstructive lesions, and less frequent causes such as bezoars, inflammatory bowel disease strictures, and volvulus. 1

Key Etiologies to Identify

The critical distinction from adhesive SBO matters because non-adhesive causes often require different management strategies and have lower success rates with conservative treatment:

• Incarcerated hernias - Second most common cause of SBO after adhesions, requires surgical repair 1
• Malignant obstruction - Primary small bowel tumors or metastatic disease (ovarian, colon, gastric) 1
• Inflammatory bowel disease - Crohn's disease strictures (can be inflammatory or fibrostenotic) 2
• Bezoars - Particularly in patients with prior gastric surgery 1
• Volvulus - Midgut volvulus or segmental small bowel volvulus 1

Diagnostic Approach

CT scan is the diagnostic technique of choice when the adhesive etiology is uncertain or when you need to identify the specific cause of obstruction 1, 2:

• CT has >90% diagnostic accuracy and can identify the location, degree, and specific cause of obstruction 2, 3
• Look for hernias at all potential sites (inguinal, femoral, umbilical, incisional, internal) 1
• Assess for masses, bowel wall thickening suggesting malignancy or inflammation 2, 3
• Evaluate for closed-loop obstruction, which requires immediate surgery 4, 3

Management Algorithm

Immediate Surgical Indications (Do NOT attempt conservative management):

Proceed directly to surgery without delay if any of the following are present 2, 4, 3:

• Signs of peritonitis on examination 1, 2
• Evidence of strangulation or bowel ischemia (fever, hypotension, continuous pain, elevated lactate, leukocytosis) 1, 5, 6
• Free perforation with pneumoperitoneum 2
• Closed-loop obstruction on CT 4, 3
• Hemodynamic instability or hypotension 3

Cause-Specific Management for Stable Patients:

Incarcerated Hernia

• Surgical repair is required - hernias causing SBO will not resolve with conservative management 1
• Manual reduction should NOT be attempted if there are signs of strangulation 5

Malignant Obstruction

• For patients with years-to-months life expectancy: surgery is the primary treatment after appropriate imaging 2
• For patients with advanced disease or poor performance status: medical management is preferable including opioids, anticholinergics, corticosteroids, and antiemetics 2
• Octreotide should be started early due to high efficacy and tolerability 2
• Consider total parenteral nutrition for patients with longer life expectancy to improve quality of life 2

Inflammatory Bowel Disease (Crohn's Disease)

• Free perforation requires emergency surgery 2
• Inflammatory strictures deserve a trial of medical therapy aimed at reducing inflammation before considering surgery 2
• Endoscopic balloon dilation is successful in 89-92% of cases for primary intestinal or anastomotic strictures 2
• Any stricture should have endoscopic biopsies to rule out malignancy 2
• Surgery is mandatory for symptomatic strictures unresponsive to medical therapy and not amenable to endoscopic dilation 2

Bezoars

• May respond to endoscopic fragmentation or enzymatic dissolution (papain, cellulase) 1
• Surgical removal if endoscopic management fails

Trial of Conservative Management (Selected Cases Only)

Conservative management can be attempted in stable patients with partial non-adhesive SBO without the contraindications listed above, but success rates are significantly lower than with adhesive SBO 1:

• NPO status, nasogastric decompression, IV fluid resuscitation, electrolyte correction 1, 2
• Water-soluble contrast (50-150 mL Gastrografin) after adequate gastric decompression 4, 7
• If contrast reaches colon within 24 hours, continue conservative management 4, 7
• If contrast does NOT reach colon at 24 hours, this predicts failure and surgery should be performed 4
• Maximum 72-hour trial is considered safe in stable patients 1, 4

Critical Pitfalls to Avoid

• Do not assume adhesive etiology just because the patient has prior surgery - up to 40% of SBO in patients with prior surgery may have non-adhesive causes 1, 8
• Do not delay surgery for incarcerated hernias - these will not resolve with conservative management 1
• In young females, always consider ovarian masses, endometriosis, or pelvic inflammatory disease as potential causes 2
• Failure to obtain adequate imaging (CT) leads to missed diagnoses of hernias, malignancy, and closed-loop obstructions 2, 3, 6
• Prolonged conservative management in non-adhesive SBO increases morbidity and mortality - have a lower threshold for surgery than with adhesive SBO 3