What is the initial approach for treating Small Bowel Obstruction (SBO)?

Initial Management of Small Bowel Obstruction

Immediate Assessment and Triage

Begin with conservative management (NPO, IV fluids, nasogastric decompression, analgesia) unless signs of peritonitis, strangulation, or ischemia are present—these require immediate surgical exploration. 1

The critical first step is identifying patients who need emergency surgery versus those suitable for conservative trial:

Red Flags Requiring Emergency Surgery

• Signs of peritonitis on physical examination 1, 2
• Suspected strangulation or intestinal ischemia 1, 2
• Closed-loop obstruction identified on imaging 1, 2
• Hypotension in the setting of SBO 1

Initial Clinical Evaluation

• Examine for abdominal distension and abnormal bowel sounds (absent or high-pitched) 3
• Check all hernial orifices including groin hernias 3, 2
• Obtain complete blood count, CRP, lactate, electrolytes, BUN/creatinine, and coagulation profile 3, 1
• Elevated CRP, leukocytosis with left shift, and elevated lactate suggest peritonitis or ischemia, though normal values cannot exclude ischemia 3, 1

Diagnostic Imaging Strategy

CT abdomen/pelvis with IV contrast is the primary diagnostic tool with >90% accuracy, far superior to plain radiography (60-70% sensitivity). 3, 1

CT Imaging Protocol

• No oral contrast is needed in suspected high-grade obstruction—the nonopacified fluid provides adequate intrinsic contrast 3
• CT identifies obstruction severity, location, etiology, and complications (ischemia, volvulus, closed-loop) 3, 1
• Imaging signs of ischemia include abnormal bowel wall enhancement, intramural hyperdensity, bowel wall thickening, mesenteric edema, ascites, pneumatosis, or mesenteric venous gas 3
• Plain radiography has limited value beyond initial clinical assessment 3

Conservative Management Protocol

Non-operative management succeeds in 70-90% of adhesive SBO cases and should be the initial approach for all patients without surgical red flags. 1, 2

Core Components

• NPO status 1, 2
• IV crystalloid resuscitation with electrolyte monitoring and correction 1, 2
• Nasogastric tube decompression—though recent evidence questions routine use in patients without active emesis, as NGT placement increases pneumonia risk and hospital length of stay 4
• Foley catheter for monitoring 1
• Analgesia for pain control 1
• Nutritional support as needed 1

Water-Soluble Contrast Challenge

Administer 100 mL hyperosmolar iodinated contrast (e.g., Gastrografin diluted in 50 mL water) orally or via enteric tube, with follow-up radiographs at 8 and 24 hours. 3

• If contrast reaches colon within 4-24 hours: predicts successful non-operative management with 96% sensitivity and 98% specificity 3, 1
• If contrast does not reach colon by 24 hours: highly predictive of need for surgery 3
• This protocol has both diagnostic and therapeutic value, significantly reducing need for surgery 3, 1
• Caveat: Water-soluble contrast may worsen dehydration due to high osmolarity, shifting fluids into bowel lumen 1
• Equally effective in patients with virgin abdomen (no prior surgery) 3

Timing of Surgical Intervention

A 72-hour trial of conservative management is safe and appropriate for patients without signs of peritonitis, strangulation, or ischemia. 3, 1, 2

Surgical Indications

• Immediate: Peritonitis, strangulation, ischemia, closed-loop obstruction, hypotension 1, 2
• After failed conservative trial: No resolution after 72 hours 1, 2
• Laparotomy remains the standard approach, though laparoscopy may be considered in hemodynamically stable patients with single adhesive band on CT and minimal bowel distension 3, 2
• Use adhesion barriers during surgery to reduce recurrence rates (from 4.5% to 2.0% at 24 months) 3, 2

Common Pitfalls and Complications

• Do not delay surgery in patients with peritonitis, strangulation, or ischemia—mortality reaches 25% with ischemia 3
• Monitor for complications: dehydration with renal injury, electrolyte disturbances, malnutrition, aspiration pneumonia 1, 2
• Recurrence risk: 12% within 1 year, increasing to 20% after 5 years with non-operative management 1, 2
• Avoid routine NGT in patients without active emesis—associated with increased pneumonia, respiratory failure, and longer hospital stays 4
• Physical exam and labs have limited sensitivity for detecting strangulation or ischemia—rely on imaging 3

Special Populations

Virgin Abdomen (No Prior Surgery)

• Adhesions remain a common cause even without prior surgery 3, 2
• Conservative management with water-soluble contrast is equally effective 3
• Surgical rates historically higher (39-83%) but can be reduced to 16% with appropriate use of water-soluble contrast protocol 3

Malignant Bowel Obstruction

• Surgery after CT is primary treatment for patients with longer life expectancy 1
• Medical management preferred for advanced disease: opioids, antiemetics, octreotide, corticosteroids 2