What are the symptoms of small bowel obstruction?

Symptoms of Small Bowel Obstruction

The classic symptoms of small bowel obstruction include colicky abdominal pain, abdominal distension, nausea and vomiting, and absence of flatus or bowel movements. 1

Cardinal Symptoms

• Colicky abdominal pain that worsens with attempts to overcome the obstruction is present in most cases 1
• Abdominal distension occurs in 65.3% of cases and is a strong predictive sign with a positive likelihood ratio of 16.8 1
• Nausea and vomiting are more prominent and occur earlier in small bowel obstruction compared to large bowel obstruction 1
• Absence of passage of flatus occurs in 90% of cases 1
• Absence of bowel movements occurs in 80.6% of cases 1
• Hyperactive or absent bowel sounds on physical examination 1
• Visible peristalsis may be seen in thin patients 1

Clinical Presentation Based on Location

• Proximal small bowel obstruction:

  • More frequent and earlier vomiting 1
  • Green/yellow bilious vomit 1
  • Less pronounced abdominal distension 2

• Distal small bowel obstruction:

  • More pronounced abdominal distension 2
  • Later onset of vomiting 1
  • More severe dehydration and electrolyte disturbances 3

Warning Signs of Complications

• Signs of strangulation or ischemia include:

  • Fever, tachycardia, tachypnea, and confusion 1
  • Intense pain unresponsive to analgesics 1
  • Diffuse abdominal tenderness, guarding, or rebound tenderness 1
  • Hypotension, cool extremities, mottled skin (signs of shock) 1

• Laboratory findings suggesting complications:

  • Leukocytosis (WBC >10,000/mm³) and neutrophilia 1, 2
  • Elevated lactic acid levels 1
  • Low serum bicarbonate levels and arterial blood pH 1
  • Elevated amylase levels 1

Differences from Other Conditions

• Small bowel obstruction vs. large bowel obstruction:

  • Small bowel obstruction has more frequent and earlier vomiting 1
  • Large bowel obstruction has more gradual development of symptoms 1
  • Recurrent left lower quadrant pain is more common in large bowel obstruction 1

• Small bowel obstruction vs. ileus:

  • Both present with abdominal distension and decreased bowel sounds 2
  • In ileus, pain is typically less colicky and more diffuse 2
  • Ileus often occurs after surgery, trauma, or with metabolic disturbances 2

Diagnostic Considerations

• CT scan is the most accurate diagnostic tool with approximately 90% accuracy 1, 2

• Signs on CT suggesting need for early surgical intervention include:

  • Abnormal bowel wall enhancement 4
  • Intramural hyperdensity on non-contrast CT 4
  • Bowel wall thickening, mesenteric edema, ascites 4
  • Pneumatosis or mesenteric venous gas 4

• Laboratory tests to consider:

  • Complete blood count to assess for leukocytosis 2
  • Electrolyte panel to identify imbalances (particularly potassium) 2
  • Renal function tests to evaluate dehydration 2
  • Lactate levels to assess for intestinal ischemia 2

Pitfalls to Avoid

• Mistaking incomplete obstruction with watery diarrhea for gastroenteritis can lead to delayed diagnosis 2
• Overlooking bowel obstruction in elderly patients where pain may be less prominent 2
• Failing to recognize signs of strangulation, which has a mortality rate of up to 25% if not promptly addressed 4
• Relying solely on plain abdominal X-rays, which have limited diagnostic value with a sensitivity of only 50-60% 1

Remember that early recognition of symptoms and prompt management are crucial to reduce morbidity and mortality in patients with small bowel obstruction 5.