From the Guidelines
A KUB X-ray is a suitable initial imaging choice for a patient suspected of having ileus, as it provides a quick and cost-effective screening tool to reveal key findings associated with ileus. This recommendation is based on the American College of Radiology's appropriateness criteria for suspected small-bowel obstruction, which suggests that abdominal radiography, including KUB, has been the traditional starting point for imaging evaluation 1. Although the accuracy of abdominal radiographs in detecting small-bowel obstruction (SBO) has yielded disparate results, with some studies reporting an 80% to 90% success rate and others achieving rates only in the 30% to 70% range, a relatively recent study found that abdominal radiographs were accurate for detecting acute SBO 1.
Some key points to consider when using KUB for ileus include:
- The supine KUB view is typically ordered first, often followed by an upright or left lateral decubitus view to better demonstrate air-fluid levels.
- The KUB can help differentiate between different types of ileus (paralytic vs. mechanical) and may identify potential causes such as fecal impaction or radiopaque foreign bodies.
- While the KUB has limitations in detecting subtle findings and may not provide definitive diagnosis in all cases, its wide availability, low radiation exposure, and ability to quickly confirm the presence of bowel obstruction make it valuable for initial assessment.
- More advanced imaging such as CT may be necessary if the diagnosis remains unclear after KUB or if complications are suspected, but the KUB remains the recommended first-line imaging study for suspected ileus, as it can provide important information to guide further management, as noted in the study published in the Journal of the American College of Radiology 1.
From the Research
KUB for Ileus
- A KUB (Kidneys, Ureters, Bladder) X-ray is not the most suitable initial imaging choice for a patient suspected of having ileus, as it has limited sensitivity and specificity in diagnosing intestinal obstruction 2, 3, 4.
- The sensitivity of plain film radiography, including KUB, for revealing small-bowel obstruction is around 69-77% 3, 4, and its specificity is around 50-57% 3, 4.
- CT scans have been shown to be more effective in distinguishing between postoperative ileus and complete mechanical small-bowel obstruction, with a sensitivity and specificity of 100% 2.
- CT scans are also valuable in diagnosing and distinguishing partial mechanical small-bowel obstruction from paralytic ileus, and in determining the level and cause of obstruction 2, 3.
- In some cases, a left-side-down decubitus view can be useful in radiographic evaluation of intussusception, particularly when the supine view is diagnostically indeterminate 5.
- Other imaging modalities, such as ultrasound and CT, may be more suitable for initial evaluation of patients suspected of having ileus, depending on the clinical presentation and suspected cause of the obstruction 3, 6, 4.