Signs and Symptoms of Bowel Obstruction
The most common signs and symptoms of bowel obstruction are absence of passage of flatus (90%) and/or feces (80.6%), abdominal distension (65.3%), and colicky abdominal pain. 1, 2
Clinical Presentation
Common Symptoms
- Colicky abdominal pain that worsens with attempts to overcome the obstruction 1
- Absence of passage of flatus (90% of cases) 1, 2
- Absence of bowel movements (80.6% of cases) 1, 2
- Nausea and vomiting (more prominent and earlier in small bowel obstruction) 1
- Abdominal bloating 1
Physical Examination Findings
- Abdominal distension (65.3% of cases) - a strong predictive sign with positive likelihood ratio of 16.8 1
- Abdominal tenderness 1
- Hyperactive or absent bowel sounds 1
- Visible peristalsis (in thin patients) 1
- Digital rectal examination may reveal blood or a rectal mass in cases of colorectal cancer 1
Warning Signs of Complications
Signs of Strangulation/Ischemia
- Fever, tachypnea, tachycardia, and confusion 1
- Intense pain unresponsive to analgesics 1
- Diffuse abdominal tenderness, guarding, or rebound tenderness 1
- Absent bowel sounds 1
- Hypotension, cool extremities, mottled skin, and oliguria (signs of shock) 1
Laboratory Findings Suggesting Complications
- Leukocytosis and neutrophilia 1, 3
- Elevated lactic acid levels 1, 3
- Low serum bicarbonate levels and arterial blood pH 1
- Elevated amylase levels 1
- Abnormal renal function tests indicating dehydration 3
Differences Between Small and Large Bowel Obstruction
Small Bowel Obstruction
- More frequent vomiting that occurs earlier in the course 1
- Green/yellow vomit in proximal obstruction 1
- Most commonly caused by adhesions (55-75% of cases) 1
Large Bowel Obstruction
- Less frequent vomiting 1
- Feculent vomiting in distal obstruction 1
- More gradual development of symptoms 1
- Recurrent left lower quadrant abdominal pain 1
- Most commonly caused by cancer (60% of cases) 1
- May present with previous complaint of bloody stools 1
Diagnostic Approach
Initial Assessment
- Complete history focusing on previous abdominal surgeries (85% sensitivity for adhesive small bowel obstruction) 3
- Inquire about previous diverticulitis episodes, chronic constipation, rectal bleeding, or unexplained weight loss 1, 3
- Examine all hernia orifices and previous surgical incision sites 1, 3
Laboratory Tests
- Complete blood count to assess for leukocytosis 3
- Electrolyte panel to identify imbalances 1, 3
- Renal function tests to evaluate dehydration 3
- Lactate levels to assess for intestinal ischemia 3
Imaging Studies
- CT scan is the most accurate diagnostic tool with approximately 90% accuracy 3
- Abdominal ultrasound can be used as an alternative with 90% sensitivity and 96% specificity 3
- Plain abdominal X-rays have limited diagnostic value (sensitivity 50-60%) 3
Common Pitfalls to Avoid
- Mistaking incomplete obstruction with watery diarrhea for gastroenteritis 3
- Overlooking bowel obstruction in elderly patients where pain may be less prominent 3, 4
- Failing to recognize signs of strangulation, which requires immediate surgical intervention 3, 5
- Not examining all potential hernia sites, especially in thin elderly patients 4
- Delaying imaging in patients with suspected obstruction 5