Indications
The indications for VCE are expanding and the authors will later discuss some of the common clinical situations where VCE will be of value (Box 1). The European Federation of Internal Medicine conducted a study on the value and indications of VCE in 2010, showing that anemia or GI bleeding was the main indication for VCE, while in cases of Crohn's disease and celiac disease, VCE was used in order to exclude significant findings or to follow up [Mustafa BF, Pers. Comm.].
Obscure GI Bleeding
Careful examination of both the upper and lower GI tract in cases of overt GI bleeding is mandatory before investigating the small intestine. VCE is indicated if the hemorrhage is occult and is thought to be from a small bowel mucosal origin. Thus, the most important indication for VCE is overt or obscure GI bleeding, with or without iron deficiency anemia (IDA). In addition, in comparison with more invasive methods of diagnosis, such as DBE, the diagnostic rates of VCE and DBE are similar; however, full examinations of the intestinal tract are much more likely with VCE.[10] In a study performed on a group of patients to compare VCE and small bowel follow-through, VCE was diagnostic for small intestinal bleeding in 31% of patients, while small bowel follow-through was only diagnostic for 5% of the patients.[11]
IDA is one of the most common presentations of obscure GI bleeding and it has several causes, which may be difficult to diagnose by conventional endoscopy. Examples of such causes include angiodysplasia or angioectasia, small bowel Crohn's disease and small bowel malignancy. Intraoperative endoscopy can also be used as a method for diagnosis if VCE fails, or as a therapeutic procedure for the findings of VCE.[12]
A meta-analysis assessing the diagnostic yield of VCE in IDA, including a total of 24 studies enrolling 1960 patients with IDA who underwent VCE, reported a pooled diagnostic yield of 47% with the caveat of statistically significant heterogeneity among the included studies. The pooled diagnostic yield in studies that focused on patients with IDA was 66.6%, compared to 44% in studies that did not focus on IDA alone.[13]
In a study of 60 patients randomized to angiography or VCE, the diagnostic yield of immediate VCE was significantly higher than angiography (53.3 vs 20.0%; p = 0.016) and comparable long-term outcomes.[14]
The positive-predictive value of VCE in cases of overt GI bleeding is about 97%, and the procedure will have a higher yield if performed during or closer to the bleeding time.[15,16] In one study, a negative VCE examination was associated with approximately 5% rate of recurrent bleeding after a median follow-up period of 19 months. Another study reported an 11% rebleeding rate.[15,17]
CT- and MRI-enteroclysis are increasingly utilized in the work-up to obscure GI bleeding. Despite advances in these imaging modalities, they are still not ideal for small flat lesions, such as in angioectasias that are commonly identified with CE in these cases. VCE is also more useful if there is active bleeding during the examination. In addition, the shorter the duration between the last bleeding and VCE, the higher the diagnostic yield.
Crohn's Disease
Crohn's disease is a type of inflammatory bowel disease (IBD) that mostly occurs in the terminal ileum and colon, which are accessible by ileocolonoscopy. However, it is also evident, in some cases, in the proximal small intestine and other parts of the GI tract. Previously, the diagnosis for Crohn's disease was through conventional endoscopy and imaging techniques. These were inadequate for assessment of disease in the small bowel.[18] Now, VCE, with the help of other techniques such as blood tests and radiological investigations, can be used for the diagnosis of small bowel Crohn's disease earlier and more easily than before. Additionally, VCE is helpful in previously diagnosed cases of Crohn's disease as a tool for follow-up.[19]
Furthermore, VCE can be helpful in cases of suspected Crohn's disease, where it is potentially able to detect more findings in cases that had positive radiological tests, and also to detect abnormalities in patients that had had radiological investigations reported as 'normal'.[18] VCE also plays an important role in cases of indeterminate colitis, where the patient has signs of Crohn's and ulcerative colitis and because conventional endoscopy cannot differentiate between these two conditions in the colon or terminal ileum. Using VCE, however, the small bowel lesions of Crohn's disease can be seen.[9]
In a study of VCE in Crohn's disease, evidence of the disease was found in 43–71% of patients in whom colonoscopy and small bowel radiology had shown normal results. VCE is also superior to push enteroscopy in cases of confirmed Crohn's disease, as it can obtain images from a greater area than push endoscopy. On the contrary, in cases of ileo–colonic resection, ileocolonoscopy may be better than VCE for detection of recurrence.[10]
One of the complications of the Crohn's disease is intestinal stricture, which may lead to capsule retention. This is an important point that should be considered prior to performing VCE. Capsule retention may lead to unexpected results and may require surgical treatment to extract the capsule. It is crucial to consider the risk of complications because, especially in patients with Crohn's disease (and some differences exist among patients with suspected or established Crohn's disease), the benefit (possible diagnosis) has to be weighed against the specific risk (retention).
Celiac Disease
Celiac disease is an autoimmune disorder, characterized by gluten-dependent enteropathy. The gold standard diagnosis is positive serology plus histopathological confirmation from biopsy obtained during esophageo–gastroduodenoscopy. VCE is not one of the daily routine investigations of celiac disease, but it can be used in suspected or equivocal cases of celiac disease, and has a better diagnostic yield in suspected cases rather than patients with known celiac disease and persisting symptoms. A meta-analysis of studies estimating accuracy of VCE in the diagnostic work-up of celiac disease, which included only 166 individuals from six studies, reported an overall pooled VCE sensitivity of 89% and specificity of 95%.[20] CE also plays an important role in the diagnosis of suspected celiac disease in patients who refuse to undergo an endoscopy. VCE has high magnification power; it can provide clear images of the small bowel wall and the villous atrophy. Other roles of VCE in celiac disease are in follow-up or during complications of the disease when patients are on a gluten-free diet. Additionally, VCE can be used in cases of surveillance of neoplastic changes in patients with celiac disease.[21]
Small Bowel Tumors
Small bowel cancer accounts for about 6% of GI malignancy, and is the second most common cause of small bowel bleeding after angioectasia. However, this percentage may not be exact as it is difficult to examine the small bowel, and radiological studies cannot detect small or early tumors. In a retrospective study, small bowel tumors were diagnosed by CE in approximately 13.7% of cases, and in the majority of them, indications for VCE were 'obscure GI bleeding'.[22] In a study of 5129 patients undergoing VCE, small bowel tumors were diagnosed by VCE in 2.4% of the patients.[23] Another retrospective analysis of the charts of 562 patients who underwent VCE reported diagnosed small bowel tumors in 8.9% of patients.[24]
NSAID Enteropathy
The mucosa of the GI tract and, in particular, the small bowel are sensitive to NSAIDs. NSAIDs can cause several lesions that can be seen using VCE, such as mucosal breaks, erosions, petechiae, diaphragms, red spots and denuded areas. The occurrence of the lesions differs from one person to another. Furthermore, NSAIDs have an effect on the permeability of the intestinal wall and can cause inflammation, even after a short course. Low-dose aspirin can also affect the intestinal mucosa. In a study undertaken with healthy volunteers receiving low-dose aspirin for 2 weeks, intestinal mucosal injuries were reported in 80% of the aspirin group compared with 20% in the control group, who received no medication.[25] There is, however, a risk of bias in such a study owing to the prevalence of minimal inflammatory changes (erosions and breaks) in control subjects undergoing VCE.
Screening for Polyps
Small bowel polyps are protrusions from the intestinal wall, and can be associated with polyposis in other parts of the GI tract. VCE can be used to screen for those at high risk of polyposis syndrome (high Spigelman stage), such as familial adenomatous polyposis and Peutz–Jegher's syndrome. VCE can detect small polyps in the middle and distal part of the small bowel, which cannot be examined by conventional endoscopy and cannot be discovered by small bowel follow-through and/or MRI.[9] However, VCE has limited sensitivity and it may detect a smaller numbers of polyps in the proximal small bowel in cases of familial adenomatous polyposis in comparison to push enteroscopy or DBE. Additionally, it has some limitations in its ability to identify large polyps and lesions in the duodenum and periampullary areas.[24,25] In highly suspicious clinical situations, enteroscopy or side-viewing duodenoscopy should be considered instead of VCE to confirm the diagnosis.
Expert Rev Gastroenterol Hepatol. 2013;7(4):323-329. © 2013 Expert Reviews Ltd.
