What is the preferred imaging modality for diagnosing small bowel obstruction (SBO)?

From the Guidelines

For small bowel obstruction (SBO), abdominal CT scan with intravenous contrast is the recommended first-line imaging modality. This recommendation is based on the most recent and highest quality study, which confirms the use and accuracy of a standard abdominal and pelvic CT examination in patients with a suspected high-grade SBO, with a diagnostic accuracy of more than 90% 1. The American College of Radiology (ACR) panel recommends CT abdomen and pelvis with IV contrast as the initial imaging modality for suspected SBO with an acute presentation, as it provides detailed information about the location, cause, and potential complications like strangulation or perforation 1.

Some key points to consider when choosing an imaging modality for SBO include:

• CT scan with IV contrast has high sensitivity (90-95%) and specificity (95%) for diagnosing SBO 1
• Plain abdominal radiographs have limited sensitivity (60-70%) and provide less detailed information, but may be performed initially due to availability and lower cost
• Ultrasound may be useful in specific populations like pregnant patients or children to avoid radiation exposure, though operator dependency limits its routine use
• MRI provides excellent soft tissue detail without radiation but is less readily available and more time-consuming, making it a second-line option
• Water-soluble contrast studies (Gastrografin) can be both diagnostic and potentially therapeutic by resolving partial obstructions through an osmotic effect

The imaging choice should be guided by clinical presentation, with CT being particularly important in cases with suspected strangulation, where early surgical intervention may be necessary to prevent bowel ischemia and necrosis 1. Multidetector CT scanners with multiplanar reconstruction capabilities have been noticeably more effective for evaluating SBO and other abdominal pathology, and CT with IV contrast is preferable for routine imaging of suspected SBO to demonstrate whether the bowel is perfusing normally or is potentially ischemic 1.

From the Research

Imaging Modalities for Diagnosing Small Bowel Obstruction (SBO)

• The preferred imaging modality for diagnosing SBO is Computed Tomography (CT) 2, 3, 4, 5, 6
• CT is recommended when clinical and initial radiographic findings remain indeterminate or strangulation is suspected 3
• CT can provide important information about the cause and site of obstruction and the presence of a closed-loop obstruction or ischemia 5

Advantages of CT in Diagnosing SBO

• CT has a sensitivity of 78%-100% for the detection of complete or high-grade small bowel obstruction 3
• CT can demonstrate pathologic processes involving the bowel wall as well as the mesentery, mesenteric vessels, and peritoneal cavity 3
• CT is superior to conventional radiography in revealing the site, level, and cause of obstruction and in demonstrating threatening signs of bowel inviability 2

Comparison with Other Imaging Modalities

• Conventional radiography should remain the initial imaging method in patients with suspected SBO, but CT is an important additional diagnostic tool when specific disease management issues must be addressed 2
• Small bowel follow-through can be used to identify "insignificant obstructions" when contrast reaches the cecum within 4 hours, but CT is superior in detecting the cause of the intestinal obstruction and presence of strangulation 6