Diagnostic Approach to Suspected Small Bowel Obstruction

Clinical Presentation and Initial Assessment

The clinical presentation of small bowel obstruction (SBO) is highly concerning and typically includes colicky abdominal pain, absence of flatus, and absence of bowel movements, with colicky abdominal pain present in the majority of SBO cases and representing the bowel's attempt to overcome the obstruction, absence of flatus occurring in 90% of SBO cases, and absence of bowel movements occurring in 80.6% of cases 1
A history of prior abdominal surgery is a significant risk factor for SBO, with adhesions being the most common cause of SBO in adults (55-75% of cases), and prior abdominal surgery having 85% sensitivity for adhesive SBO 1

Immediate evaluation for signs of strangulation/ischemia or perforation is crucial, as these conditions require emergency surgical intervention, with signs including fever, tachycardia, tachypnea, or confusion, intense pain unresponsive to analgesics, diffuse abdominal tenderness, guarding, or rebound tenderness, absent bowel sounds, and signs of shock 1, 2

A focused physical examination should be performed to look for abdominal distension, abdominal tenderness and peritoneal signs, bowel sounds, and to examine all hernia orifices and previous surgical incision sites 1
Laboratory studies, including complete blood count, lactate level, electrolyte panel, renal function tests, and arterial blood gas, should be ordered immediately to assess for complications and metabolic derangements 1
A CT scan of the abdomen and pelvis with IV contrast is the diagnostic test of choice, with approximately 90% accuracy, and should be obtained urgently in cases of high clinical suspicion 1

Resuscitation should be started immediately, with NPO status, IV fluid resuscitation, nasogastric tube placement, and analgesia, and immediate surgical consultation should be obtained 2
If complete obstruction with signs of strangulation is present, emergency surgical intervention is required, with signs including bowel wall thickening, pneumatosis, or portal venous gas, mesenteric edema or free fluid, closed-loop obstruction, and lack of contrast passage 1, 2
If partial obstruction without strangulation is present, a trial of nonoperative management may be considered, with continued bowel rest and NG decompression, water-soluble contrast administration, and close monitoring for clinical deterioration 1