What is the best imaging modality for diagnosing Small Bowel Obstruction (SBO)?

From the Guidelines

Computed tomography (CT) with intravenous contrast is the best imaging modality for diagnosing small bowel obstruction (SBO). When a patient presents with symptoms suggestive of SBO such as abdominal pain, distension, vomiting, and constipation, a CT scan should be promptly ordered as it provides detailed visualization of the bowel, potential transition points, and possible causes of obstruction. The sensitivity of CT for SBO diagnosis ranges from 90-96%, making it superior to plain radiographs (X-rays), which only have a sensitivity of 50-60% 1. CT can identify not only the presence of an obstruction but also its location, severity (partial vs. complete), and etiology (adhesions, hernias, tumors, etc.), as well as complications like ischemia or perforation.

Key Benefits of CT

• High diagnostic accuracy for SBO, with a sensitivity of over 90% 1
• Ability to identify the location, severity, and etiology of the obstruction
• Capability to detect complications such as ischemia or perforation
• Guidance for management, including assessment of SBO complications and potential etiologies

Comparison to Other Imaging Modalities

• Plain radiographs (X-rays) have a lower sensitivity of 50-60% and may not provide sufficient information for diagnosis or management 1
• Ultrasound can be considered as an alternative in settings where CT is unavailable, particularly in pregnant patients or children, but it is operator-dependent and may not provide as comprehensive information as CT 1

Clinical Recommendations

• CT with intravenous contrast should be the initial imaging modality of choice for suspected SBO
• Abdominal X-rays may be obtained initially due to availability and lower cost, but they should not delay definitive CT imaging if SBO is strongly suspected
• Ultrasound can be considered as an alternative in specific situations, but CT remains the preferred imaging modality for SBO diagnosis and management 1

From the Research

Imaging Modalities for SBO Diagnosis

• Computed Tomography (CT) scan is a valuable modality for diagnosing Small Bowel Obstruction (SBO), with a sensitivity of 92% and specificity of 71% 2.
• CT scan is superior to plain film radiography in diagnosing SBO, with plain films having a sensitivity of 75% and specificity of 53% 2.
• A CT scoring system can predict the need for surgery in SBO, with a score of 8 or higher predicting the need for surgery 75% of the time 3.

CT Scan Findings in SBO

• CT scan can identify complete obstruction, dilated small bowel, and free fluid, which are indicative of SBO 3.
• The presence of these findings can predict the need for operative intervention in 79% of cases with SBO 3.
• CT scan can also diagnose ischemia in SBO, with a sensitivity of 83% and specificity of 92% 4.

Comparison with Other Imaging Modalities

• CT scan is superior to small bowel follow-through in identifying masses, malignancies, and features of strangulation 5.
• Small bowel follow-through can correctly identify "insignificant obstructions" when contrast reaches the cecum within 4 hours 5.
• Multidetector CT is a powerful tool for assessing patients with SBO, providing important information about the cause and site of obstruction and the presence of a closed-loop obstruction or ischemia 6.