From the Guidelines
For rectal bleeding, a CT abdomen and pelvis with IV contrast is the preferred imaging study, not a CTA abdomen. This recommendation is based on the most recent evidence from the American College of Radiology, which suggests that CT with IV contrast provides adequate visualization of the gastrointestinal tract, potential sources of bleeding, and surrounding structures without the higher radiation dose and arterial timing required for CTA 1. The contrast-enhanced CT can identify common causes of rectal bleeding such as diverticular disease, inflammatory bowel disease, neoplasms, and vascular abnormalities.
Key Points to Consider
- CTA would be more appropriate if active arterial bleeding is strongly suspected and interventional radiology consultation is being considered for potential embolization 1.
- The standard CT with contrast offers sufficient diagnostic information for most cases of rectal bleeding while allowing visualization of the entire abdomen and pelvis, which is important as the source of bleeding may be located anywhere in the lower gastrointestinal tract.
- Additionally, the pelvis must be included in the scan as rectal pathology would otherwise be missed if only the abdomen were imaged.
- The use of IV contrast is preferred to a noncontrast examination to help visualize and characterize fluid collections, abscesses, and fistulous tracts, as noted in the ACR Appropriateness Criteria for anorectal disease 1.
Imaging Protocol
- The CT protocol for imaging a patient with an anorectal complaint depends upon the presentation and differential diagnosis, but IV contrast is generally preferred 1.
- Water-soluble rectal contrast may be useful in certain scenarios, such as diagnosing a rectal abscess or perforation, but is not typically necessary for rectal bleeding 1.
From the Research
Imaging for Rectal Bleeding
- For patients presenting with rectal bleeding, imaging studies are crucial in identifying the cause and severity of the bleeding.
- According to 2, CT is the best first-line imaging tool to identify abdominal hemorrhage, including rectal bleeding, and has been shown to be superior in detecting intra-abdominal bleeding compared to angiography.
- A CT abdomen and pelvis with contrast may be the most appropriate imaging study for rectal bleeding, as it can help identify the source of bleeding and guide management.
Diagnostic Evaluation of Rectal Bleeding
- Rectal bleeding can be caused by a range of conditions, from benign to life-threatening, and a thorough diagnostic evaluation is essential to determine the underlying cause 3, 4.
- The diagnostic evaluation of rectal bleeding may involve a combination of medical history, physical examination, laboratory tests, and imaging studies, including CT scans and colonoscopies 5, 6.
- Guidelines recommend that patients with rectal bleeding undergo a colonoscopy to rule out colorectal cancer, especially if they are over 50 years old or have a family history of the disease 5.
Choice of Imaging Study
- While ultrasound may be used in the initial evaluation of trauma patients, it is not sensitive for subtle bleeds or injuries, and CT is generally preferred for identifying abdominopelvic hemorrhage 2.
- A CT abdomen and pelvis with contrast can provide more detailed information about the source and severity of rectal bleeding, and can help guide management and treatment decisions.
- However, the choice of imaging study may depend on the specific clinical presentation and patient factors, and should be determined on a case-by-case basis.