From the Guidelines
To evaluate a possible small bowel obstruction, a CT scan of the abdomen and pelvis with IV contrast is the most accurate diagnostic test and is considered the gold standard. This is based on the most recent and highest quality study available, which reported a diagnostic accuracy of more than 90% for CT scans in patients with suspected small-bowel obstruction 1. The use of CT scans can help identify the location and cause of the obstruction, detect complications like strangulation or perforation, and determine if surgical intervention is needed.
Some key points to consider when using CT scans for diagnosing small bowel obstruction include:
- The use of oral contrast medium is not necessary in patients with a suspected high-grade obstruction, as the nonopacified fluid in the bowel provides adequate intrinsic contrast 1.
- Multidetector CT scanners with multiplanar reconstruction capabilities have been shown to be more effective for evaluating small-bowel obstruction and other abdominal pathology 1.
- CT scans can also help identify the underlying cause of obstruction, such as adhesions, hernias, or malignancies, and can predict the need for emergency surgery 1.
In addition to CT scans, other diagnostic tests that may be used to evaluate small bowel obstruction include:
- Abdominal X-ray (plain radiograph), which can show dilated bowel loops and air-fluid levels, but is not as accurate as CT scans 1.
- Small bowel follow-through using barium or water-soluble contrast, which can assess the degree of obstruction and potentially treat partial obstructions 1.
- Ultrasound, which can be useful in pediatric patients or pregnant women to avoid radiation exposure 1.
- Laboratory tests, including complete blood count, electrolytes, and lactate levels, which can help assess for complications like dehydration, electrolyte imbalances, or ischemia 1.
Overall, the choice of diagnostic test will depend on the individual patient's presentation and clinical scenario, but CT scans with IV contrast are generally the preferred initial imaging test for suspected small bowel obstruction 1.
From the Research
Evaluation of Small Bowel Obstruction
To evaluate possible small bowel obstruction, several tests can be used, including:
Computed Tomography (CT) Scan
CT scan is a powerful tool for assessing patients with small bowel obstruction and can:
- Confirm the presence of small bowel obstruction 3, 4, 6
- Show the site, level, and cause of obstruction accurately 3, 4
- Detect strangulation 3, 4
- Identify masses, malignancies, and features of strangulation 2
- Predict the need for surgery using a scoring system based on radiographic criteria 5
Small Bowel Follow-Through Study
Small bowel follow-through study can:
- Correctly identify "insignificant obstructions" when contrast reaches the cecum within 4 hours 2
- Be used in patients with equivocal findings of small bowel obstruction, after CT scan 2
Comparison of Tests
CT scan has been shown to be superior to plain abdominal films in diagnosing small bowel obstruction, with a sensitivity of 92% and specificity of 71% 6. CT scan is also superior to small bowel follow-through study in identifying masses, malignancies, and features of strangulation 2. However, small bowel follow-through study can still be useful in certain cases, such as when CT scan is not diagnostic 2.