Initial Management of Small Bowel Obstruction
The initial management of small bowel obstruction (SBO) must begin with prompt supportive treatment including intravenous crystalloids, nasogastric tube decompression, and bowel rest. 1
Assessment and Diagnosis
Clinical Evaluation
Look for key symptoms and signs:
- Colicky abdominal pain
- Nausea and vomiting (earlier and more prominent in SBO)
- Abdominal distension (strong predictive sign with positive likelihood ratio of 16.8)
- Constipation to obstipation
- Abnormal bowel sounds
- History of previous abdominal surgery (present in 80% of cases)
Warning signs requiring urgent surgical evaluation:
- Peritoneal signs (rebound tenderness, guarding)
- Signs of ischemia (severe unrelenting pain, fever)
- Hemodynamic instability
- Marked leukocytosis, acidosis, or elevated lactate
Laboratory Testing
- Complete blood count
- Renal function and electrolytes (to detect pre-renal acute renal failure)
- Liver function tests
- Serum bicarbonate, arterial blood pH, lactic acid level (if ischemia suspected)
- Coagulation profile (in anticipation of possible surgery)
Imaging
Abdominal plain X-ray:
CT scan:
- Preferred imaging technique for diagnosis and determining need for urgent surgery 1
- Can identify closed loop obstruction, ischemia, and free fluid (signs suggesting need for immediate surgery)
- Can differentiate between complete and partial obstruction
- Helps determine location of obstruction
Water-soluble contrast studies:
- Both diagnostic and potentially therapeutic
- If contrast reaches the colon within 24 hours, high likelihood of successful non-operative management
- If contrast does not reach colon after 24 hours, indicates likely failure of non-operative management 1
Initial Management Protocol
1. Resuscitation and Supportive Care
Fluid resuscitation:
- Isotonic crystalloids with supplemental potassium
- Volume equivalent to patient's losses 1
- Monitor urine output with Foley catheter
Bowel decompression:
Nil per os (NPO) status
Electrolyte correction and acid-base balance management
Analgesia for pain control
2. Non-operative Management
- Non-operative management should be attempted in all patients with SBO unless there are signs of peritonitis, strangulation, or bowel ischemia 1
- Effective in approximately 70-90% of patients with adhesive SBO 1
- Duration of non-operative trial:
- Most experts consider a 72-hour period as safe and appropriate 1
- Continuing beyond 72 hours with persistent high output from decompression tube remains debatable
3. Indications for Immediate Surgical Intervention
- Peritonitis
- Signs of strangulation or bowel ischemia
- Clinical deterioration despite conservative management
- Complete obstruction with signs of closed loop
- Free intraperitoneal fluid on imaging
Special Considerations
SBO in Virgin Abdomen
- CT scan is essential as etiology may differ from post-surgical adhesions
- Causes include congenital adhesions, internal hernias, malignancy, and inflammatory conditions 1
- Management principles remain similar to adhesive SBO
Complications to Monitor
- Dehydration with kidney injury
- Electrolyte disturbances
- Malnutrition
- Aspiration pneumonia
- Bowel ischemia and perforation
Pitfalls and Caveats
- Do not delay surgical consultation in patients with concerning signs
- Nasogastric tube placement has been associated with increased risk of pneumonia and respiratory failure in some studies 2
- Plain radiographs alone cannot exclude SBO diagnosis
- CT scan findings can be misleading in up to 20% of cases 1
- Water-soluble contrast studies should not delay surgical intervention when indicated
By following this algorithmic approach to the initial management of small bowel obstruction, clinicians can optimize outcomes while minimizing morbidity and mortality associated with delayed diagnosis or inappropriate management.