From the Guidelines
For a patient with an abdominal x-ray showing distended bowel loops suggesting ileus or obstruction, a CT scan with IV contrast is recommended. This is based on the most recent and highest quality study by 1, which suggests that CT abdomen and pelvis with IV contrast is usually appropriate for the initial imaging of a suspected small-bowel obstruction with an acute presentation. The use of IV contrast provides superior visualization of the bowel wall, mesentery, and surrounding structures, helping to identify the specific location and cause of the obstruction, differentiate between mechanical obstruction and paralytic ileus, and detect complications such as ischemia, perforation, or strangulation.
The study by 1 also notes that oral contrast is not necessary and may delay the scan in acute settings. Additionally, the study by 1 confirms that CT with IV contrast has a high diagnostic accuracy of more than 90% in detecting small-bowel obstruction and can provide valuable information about the underlying cause of obstruction. The study by 1 also supports the use of CT with IV contrast, stating that it provides an excellent evaluation of the bowel wall, its vessels, and mesentery-mesocolon, and can accurately stage neoplastic bowel obstruction and identify superimposed complications.
In cases where IV contrast is contraindicated, such as in patients with renal insufficiency or contrast allergy, a non-contrast CT can still provide valuable information about bowel dilation and possible transition points, though with less detail about vascular structures and bowel wall enhancement. The patient should be kept NPO (nothing by mouth) until the scan is completed, and surgical consultation should be considered given the concerning x-ray findings, as bowel obstruction may require urgent intervention.
Key points to consider:
- CT scan with IV contrast is the preferred imaging approach for suspected small-bowel obstruction
- Oral contrast is not necessary and may delay the scan in acute settings
- Non-contrast CT can be used if IV contrast is contraindicated
- Surgical consultation should be considered given the concerning x-ray findings.
From the Research
Diagnostic Approach
- The abdominal x-ray suggests a possible ileus or obstruction pattern, with distended loops of bowel throughout the abdomen and pelvis.
- To further evaluate this condition, a CT scan may be ordered, and the question arises whether to use contrast or not.
Use of Contrast in CT Scans
- A study from 1995 2 found that CT scans were effective in distinguishing between postoperative ileus and complete mechanical small-bowel obstruction, with a sensitivity and specificity of 100%.
- However, the use of contrast in CT scans for bowel obstruction is not always necessary, as shown in a 2019 study 3, which found that unenhanced CT had a similar sensitivity to enhanced CT in identifying the etiology of bowel obstruction.
- The same study 3 suggested that in certain cases, such as adhesions with normal bowel wall thickening or neoplasms identified on unenhanced CT, an intravenous contrast agent may be avoided.
Alternative Diagnostic Methods
- Ultrasound examination can also provide important information in diagnosing bowel obstruction, as shown in a 1998 study 4, which highlighted the use of ultrasound in detecting dilated intestinal loops, gas caps, and other sonographical findings.
- However, ultrasound may have limitations in detecting certain causes of bowel obstruction, such as intestinal adhesions.
Management and Treatment
- A 2007 study 5 found that 43.3% of patients with mechanical obstruction diagnosed by CT scan eventually needed surgical treatment, while 20% of patients with ileus may still require surgical intervention.
- The use of alternative contrast media, such as carbon dioxide, gadolinium, or dilute iodinated contrast material, may be considered in patients with iodinated contrast allergy or renal dysfunction, as discussed in a 2013 review article 6.