Approximately 40% of Crohn's disease patients have disease involving both the small bowel and colon. Another one third has disease confined to the small bowel, primarily the ileum.10
The small bowel is notoriously difficult to evaluate. Wireless capsule endoscopy (WCE), initially developed for small bowel investigations in patients with occult bleeding, has been studied in small bowel Crohn's disease. Over 10
000 WCE examinations have been performed for a variety of indications worldwide with a complication rate of 0.75%.11
WCE enables a painless and radiation free examination of much of the small bowel in an unsedated patient. The patient swallows a capsule which contains a videochip, transmitter, and battery; video images are transmitted to a portable device and later downloaded to a computer. The images are usually interpreted by a gastroenterologist. Small bowel transit time is approximately four hours; the capsule is passed through the stool in 24–48 hours. Equipment costs range form $US20
000 to $30
Interpretation time varies from 30 minutes to two hours, depending on experience, but is typically one hour.12
WCE is emerging as a modality, superior to other conventional studies. The first published articles on the use of WCE in suspected small bowel diseases appeared in 2002. Costamagna and colleagues13
compared WCE to SBFT in 20 patients who underwent both barium x
ray and WCE. The barium study was deemed diagnostic in four of 20 patients; WCE was diagnostic in nine of 20. Among the first studies dealing exclusively with inflammatory bowel disease was a paper by Fireman and colleagues14
who reported a 71% yield in diagnosing small bowel Crohn's disease by WCE. Twelve of 17 patients with a normal colonoscopy and small bowel x
ray, but with a high clinical suspicion of having Crohn's disease, were found to have lesions regarded as consistent with the condition.15
These lesions were mucosal erosions, ulcers, and strictures, interpreted as suggestive of Crohn's disease. What actually constitutes Crohn's disease remains debatable. Ge and colleagues16
prospectively reviewed 20 patients with suspected Crohn's disease and a normal SBFT. Thirteen of 20 patients (65%) were found to have small bowel lesions, including erosions, aphthous ulcers, nodularity, and ulcerated stenosis. Two other studies likewise reported that WCE yielded information supporting the diagnosis of Crohn's disease in suspected patients with a normal colonoscopy and small bowel x
ray in nine of 21 patients in one study17
and in 30 of 50 patients in another.18
Liangpunsakul and colleagues19
assessed 40 patients with a negative SBE and colonoscopy. WCE detected small bowel ulcers, suggestive of Crohn's disease in three patients; SBE detected no ulcerations. A prospective study by Voderholzer and colleagues20
compared WCE with computerised tomography (CT) enteroclysis in 22 patients, eight of whom had Crohn's disease. While WCE identified small bowel lesions in seven of eight patients, CT enteroclysis was abnormal in five of eight patients. In another prospective study by the same author in 2005, the frequency of small intestinal Crohn's disease detected by WCE was double that found on CT enteroclysis (p
The gain was mainly due to detection of small mucosal lesions such as erosions and aphthous ulcerations in the jejunum and proximal ileum. There was no significant difference in the detection of lesions in the terminal ileum. Eliakim and colleagues22,23
compared the diagnostic yield of WCE and CT enteroclysis in 35 patients with suspected Crohn's disease. WCE identified erosions, aphthous ulcers, erythema, and lymphoid hyperplasia in 77% of patients. SBFT and CT enteroclysis identified abnormalities of wall thickening, nodularity of the terminal ileum, and ulcerations in 50% of patients. It remains to be determined to what degree these mucosal changes can be deemed to represent Crohn's disease, but undoubtedly for many, true Crohn's disease lesions are uncovered with WCE that had not previously been recognised with SBFT, SBE, or CT enteroclysis.
WCE appears to be safe in the paediatric population. Arguelles‐Arias and colleagues24
found that WCE was well tolerated in adolescents aged 12–16 years and identified lesions compatible with Crohn's disease in 58% of patients with a previous negative gastroscopy, colonoscopy, and small bowel x
ray. Likewise, Barkay demonstrated good tolerance in adolescents being evaluated for enteropathy.25
Because of the difficulty in swallowing the capsule, it may need to be placed endoscopically in very young children.
WCE is more sensitive than conventional modalities. It is easy to perform and is well tolerated by patients. The question is whether WCE should become an initial investigation in the diagnosis of or in the re‐evaluation of Crohn's disease. Despite its attributes, WCE has disadvantages. It is expensive. Lesions can be missed due to poor bowel preparation, rapid or delayed small bowel transit time, or orientation of the camera away from a lesion. WCE does not allow biopsy or therapeutic intervention. The ability to determine the exact locations of small bowel lesions is limited other than when they are in the proximal duodenum or the terminal ileum. As WCE is a video representation of the intestinal mucosa, it does not assess the extraluminal manifestations of the disease. The absence of a clear definition of normal versus Crohn's disease remains problematic. WCE is more sensitive than small bowel x
ray studies but specificity and positive predictive values are not established.15
The significance of red spots, erosions, and mucosal breaks, described in the literature, is not known. Fourteen per cent of asymptomatic patients have aphthous ulcers on WCE.15
Sixty eight to seventy one per cent of patients receiving anti‐inflammatory medications have small bowel erosions.26,27
Prospective studies with adequate controls and predetermined end points are necessary to define normality and validate the use of the capsule in early or mild disease.
The capsule can become lodged in a stricture, necessitating surgery. In the largest reported series of 900 patients, evaluated primarily for obscure bleeding, capsule retention occurred in 0.7% of patients.28,29
Current practice is that a small bowel x
ray is obtained prior to WCE evaluation in Crohn's disease. Alternatively, the evolution of the patency capsule may negate this precautionary measure. Recently developed in Israel, the patency capsule is not yet widely available. If retained in the gastrointestinal tract the patency capsule disintegrates; its fragments are theoretically able to pass through strictures. Boivin and colleagues30
studied the patency capsule in 22 patients with suspected small bowel strictures or radiographic small bowel strictures. Sixteen patients passed an intact capsule despite radiological stenosis. Disintegration of the capsule occurred in five patients. In one patient the capsule had to be removed surgically. Although promising, the role of the patency capsule is not fully defined. Occasionally lodging of a capsule in a stricture in Crohn's disease may help delineate an important site of disease that will likely require surgical intervention.
Wireless capsule endoscopy
- WCE is more sensitive than conventional imaging modalities.
- Specificity and positive predictive values for WCE have not been established.
- Because of the costs relative to conventional imaging and the inability to take tissue samples, WCE is unlikely to become the primary modality to initiate a diagnosis of CD in routine cases.
- WCE can diagnose small bowel disease in some instances when CD has been considered and conventional tests are negative.
- WCE is not an essential tool to diagnose CD when extent is known or when documenting the extent of disease will not affect management.
Based on cost effectiveness, funding issues, and the inability to take tissue samples, it is unlikely that WCE will become the primary imaging modality used to initiate a diagnosis of Crohn's disease or define its extent at possible relapse. WCE can diagnose small bowel disease in some instances where the disease is considered and conventional imaging is negative. It is not a necessary tool to diagnose Crohn's disease when the extent is known or when the extent of the disease will not affect management. If the disease is known and management will be affected by further defining recurrent disease WCE can be of value.
Figure 1 is an example of WCE diagnosing Crohn's disease in a patient where other modalities failed to clinch the diagnosis.
Figure 1(A, B) Wireless capsule endoscopy (WCE) images of a 47 year old female with a longstanding history of abdominal pain, previously labelled as irritable bowel syndrome and a history of depression. One year previously she presented (more ...)