Do ileus (intestinal obstruction) require computed tomography (CT) or X-ray (radiograph)?

From the Guidelines

CT scans are generally preferred over X-rays for diagnosing ileus due to their superior detail and ability to identify underlying causes and complications. An abdominal X-ray is often the initial imaging study due to its availability, low cost, and ability to show dilated bowel loops and air-fluid levels characteristic of ileus 1. However, CT provides more information, including the site and cause of the obstruction and complications of ileus, which can influence patient management 1. For patients with suspected ileus, a supine and upright abdominal X-ray series can be a reasonable first step, especially in straightforward cases or when CT is not readily available. If the diagnosis remains unclear after X-ray or if complications are suspected, a CT scan with oral and intravenous contrast should be performed 1. The choice between imaging modalities should consider the clinical presentation, availability of resources, and the patient's condition, with CT being particularly valuable in complex cases or when surgical intervention might be necessary.

Key Points to Consider

• Abdominal X-rays have limited sensitivity and specificity for diagnosing ileus, ranging from 50-60% diagnostic, 20-30% inconclusive, and 10-20% misleading 1.
• CT scans have a diagnostic accuracy of more than 90% for suspected high-grade small-bowel obstruction and can identify the cause of obstruction and complications such as ischemia and strangulation 1.
• The use of oral contrast agents in CT scans for suspected high-grade small-bowel obstruction is not necessary and can delay diagnosis and increase patient discomfort 1.
• Multidetector CT scanners with multiplanar reconstruction capabilities are more effective for evaluating ileus and other abdominal pathology 1.

Recommendations

• Use CT scans as the preferred imaging modality for diagnosing ileus, especially in complex cases or when surgical intervention might be necessary.
• Consider abdominal X-rays as an initial imaging study in straightforward cases or when CT is not readily available.
• Use oral and intravenous contrast in CT scans to provide more detailed information about the underlying cause and complications of ileus.

From the Research

Diagnostic Imaging for Ileus

• Computed Tomography (CT) scans are commonly used to evaluate intestinal obstruction and ileus, with a significant proportion of patients undergoing CT scans for diagnosis and management 2.
• CT scans have high sensitivity, specificity, and accuracy in diagnosing intestinal obstruction, and are superior to plain radiography and ultrasound in determining the level and cause of obstruction 3.
• Plain abdominal X-rays can provide important diagnostic information, especially when used in serial examinations, and can help diagnose different types of ileus, including spastic, hypotonic, mechanical, and paralytic ileus 4, 5.
• However, plain abdominal films may not be adequate for diagnosing certain conditions, such as gallstone ileus, and CT scans are often considered the gold standard in these cases 6.

Comparison of Imaging Modalities

• CT scans have been shown to be more accurate than plain radiography and ultrasound in diagnosing intestinal obstruction, with a sensitivity of 93%, specificity of 100%, and accuracy of 94% 3.
• Plain radiography has a lower sensitivity and specificity, with a sensitivity of 77%, specificity of 50%, and accuracy of 75% 3.
• Ultrasound has a sensitivity of 83%, specificity of 100%, and accuracy of 84%, but is not as effective as CT scans in determining the level and cause of obstruction 3.

Clinical Implications

• The choice of imaging modality depends on the clinical presentation and suspected diagnosis, with CT scans often being the preferred choice for evaluating intestinal obstruction and ileus 2, 3, 6.
• Plain abdominal X-rays can still provide valuable diagnostic information, especially in serial examinations, and can help guide further management 4, 5.