What are the signs of bowel obstruction?

Signs of Bowel Obstruction

Bowel obstruction presents with a classic tetrad: colicky abdominal pain, absence of flatus passage (90% of cases), absence of bowel movements (80.6%), and abdominal distension (65.3%), with distension being the strongest predictive sign (positive likelihood ratio 16.8). 1, 2

Cardinal Symptoms

• Colicky abdominal pain that worsens intermittently as the bowel attempts to overcome the obstruction 1
• Absence of flatus passage occurs in 90% of cases 1, 2
• Absence of bowel movements occurs in 80.6% of cases 1, 2
• Nausea and vomiting are universal symptoms, appearing more prominently and earlier in small bowel obstruction 1, 3
• Abdominal bloating is commonly reported 1

Physical Examination Findings

• Abdominal distension is present in 65.3% of cases and has the strongest predictive value (positive likelihood ratio 16.8) 1, 2
• Abdominal tenderness on palpation 1
• Hyperactive bowel sounds early in obstruction, or absent bowel sounds in advanced cases or with strangulation 1, 3
• Visible peristalsis may be observed in thin patients 1
• Digital rectal examination may reveal blood or a rectal mass, particularly in colorectal cancer cases 1

Critical Warning Signs of Strangulation/Ischemia

These signs indicate surgical emergency and require immediate intervention:

• Fever, tachypnea, tachycardia, and confusion 1, 3
• Intense pain unresponsive to analgesics 1
• Diffuse abdominal tenderness, guarding, or rebound tenderness indicating peritonitis 1, 3
• Absent bowel sounds 1
• Signs of shock: hypotension, cool extremities, mottled skin, oliguria 1
• Leukocytosis and neutrophilia (>10,000/mm³) 1, 4
• Elevated lactic acid levels 1, 4
• Low serum bicarbonate and arterial pH 1
• Elevated amylase levels 1

Distinguishing Small vs. Large Bowel Obstruction

Small Bowel Obstruction

• More frequent and earlier vomiting 1, 3
• Green/yellow vomit in proximal obstruction 1
• Most commonly caused by adhesions (55-75% of cases) from prior abdominal surgery 5, 1
• History of previous abdominal surgery has 85% sensitivity and 78% specificity for adhesive small bowel obstruction 5, 4

Large Bowel Obstruction

• Less frequent vomiting with more gradual symptom development 1
• Feculent vomiting may occur in distal obstruction 1
• Recurrent left lower quadrant pain 1
• Most commonly caused by cancer (60% of cases) 5, 1
• Previous bloody stools may be reported 1

Common Diagnostic Pitfalls to Avoid

• Do not mistake incomplete obstruction with watery diarrhea for gastroenteritis – this leads to dangerous delays in diagnosis 1, 4
• Do not overlook bowel obstruction in elderly patients where pain presentation may be atypical or less prominent 1, 4
• Always examine all hernia orifices and previous surgical incision sites – incarcerated hernias carry significantly higher strangulation risk 5, 4, 2
• Physical examination has only 48% sensitivity for detecting strangulation – maintain high clinical suspicion and obtain imaging promptly 4

Essential Initial Assessment

• Document last defecation and flatus passage 5, 4
• Obtain complete surgical history – this single factor has 85% sensitivity for adhesive obstruction 5, 4
• Check vital signs for shock indicators 4
• Order CT scan with IV contrast – this is the most accurate diagnostic tool with approximately 90% accuracy 1, 4
• Begin immediate supportive treatment: IV crystalloids, nasogastric tube decompression, Foley catheter, bowel rest 4, 3