From the Guidelines
Colonoscopy is the best imaging study to evaluate a patient for colonic abnormality associated with iron deficiency anemia and low ferritin levels. This procedure allows direct visualization of the entire colon and rectum, enabling detection of potential sources of gastrointestinal bleeding such as colorectal cancer, polyps, inflammatory bowel disease, or angiodysplasia that could be causing the iron deficiency. During colonoscopy, tissue samples can be obtained for biopsy and therapeutic interventions can be performed if needed, such as polyp removal. The procedure typically requires bowel preparation the day before, usually with a prescribed laxative solution, and is performed under sedation. Iron deficiency anemia in adults, particularly in men and postmenopausal women, often suggests gastrointestinal blood loss, and colorectal cancer must be ruled out. While other imaging studies like CT colonography might be considered as alternatives in specific situations, they don't allow for tissue sampling or immediate intervention, making colonoscopy the gold standard first-line investigation in this clinical scenario, as recommended by the British Society of Gastroenterology guidelines 1 and the American Gastroenterological Association (AGA) clinical practice guidelines 1.
Some key points to consider when evaluating a patient for colonic abnormality associated with iron deficiency anemia include:
- The AGA recommends using a cutoff of 45 ng/mL over 15 ng/mL when using ferritin to diagnose iron deficiency 1
- Bidirectional endoscopy, including colonoscopy, is recommended for asymptomatic postmenopausal women and men with iron deficiency anemia 1
- Noninvasive testing for Helicobacter pylori, followed by treatment if positive, may be considered in patients with iron deficiency anemia 1
- CT colonography is a reasonable alternative to colonoscopy in patients who are not suitable for colonoscopy 1
Overall, colonoscopy is the preferred imaging study for evaluating patients with iron deficiency anemia and low ferritin levels, due to its ability to directly visualize the colon and rectum, obtain tissue samples, and perform therapeutic interventions if needed, as supported by the highest quality evidence from recent studies 1.
From the Research
Imaging Studies for Colonic Abnormality
To evaluate a patient for colonic abnormality associated with iron deficiency anemia and low ferritin levels, the following imaging studies can be considered:
- Colonoscopy: This is a commonly recommended procedure for patients with unexplained iron deficiency anemia, particularly in men and postmenopausal women 2, 3, 4.
- CT-colonography: This can be used as an alternative to colonoscopy, especially in cases where colonoscopy is incomplete 5.
- Capsule endoscopy and enteroscopy: These may also be used to investigate iron deficiency anemia, particularly in cases where the small intestine is suspected to be the source of bleeding 3.
Diagnostic Yield of Imaging Studies
The diagnostic yield of these imaging studies can vary:
- Colonoscopy has been shown to have a high diagnostic yield for colonic neoplasia, with a prevalence of advanced colonic neoplasia of 7.9% in patients with ferritin < or =50 ng/mL 2.
- CT-colonography has been shown to have a diagnostic yield of 19.1% for relevant additional lesions in patients with incomplete colonoscopy 5.
- The use of serum ferritin as a marker to stratify those at risk for colonic neoplasia is still being investigated, but it may have potential utility in the assessment of colonic neoplasia 4.
Considerations for Imaging Studies
When choosing an imaging study, the following considerations should be taken into account: