Capsule Endoscopy in Crohns Disease

Video capsule endoscopy (VCE) is a new, noninva-sive imaging technique for the complete small bowel. The video capsule is a small device with a diameter of 11 mm and a length of 26 mm, which can be swallowed. It contains six light-emitting diodes, a lens, a colour camera chip and two batteries. The video capsule obtains two images per second. Video images are transmitted by means of radiotelemetry to the sensor array attached to the body with a belt. Images from a period of time as long as 8 h are stored in a portable recorder.

There are no standard preparations before the examination: certain operators prescribe only a liquid diet after lunch on the day preceding the capsule endoscopy and a fast for 8 h before the procedure.

Others recommend more complex preparation with various combinations of laxatives [sennoside, polyethylene glycol (PEG) solution]. After swallowing the capsule endoscope with 100-200 ml of water containing 100 mg of simethicone, the patient could drink 2 h later and eat 4 h later. In patients who have undergone gastric surgery or those with gastropare-sis, the video capsule could be inserted endoscopical-ly in the small intestine. Stomach passage takes an average of 34 min, and passes through the small intestine in about 4 h. Complete visualisation of the small bowel up to the caecum is achieved in 80% of patients. Most operators recommend a plain abdominal X-ray be performed 7-14 days after the examination if the capsule examination does not show images of the colon and the patient does not see the capsule passage in the stool. The capsule is designed to be used once, and after it is passed with the stool, it is not reusable [64]. On completion of the examination, the recorded images are downloaded and converted into a movie by connecting the recorder to a workstation. Data are reviewed by an operator in about 1 h with dedicated software.

The main contraindication is the presence of small-bowel stenosis that may lead to capsule retention and obstruction (see below). Other contraindications are a patient with difficulty swallowing, pregnancy or the presence of implanted medical devices such pacemakers. Capsule endoscopy is very useful in the management of patients with suspected small-bowel disease.

The diagnosis of Crohn's disease is difficult. Current radiologic and endoscopic studies are limited in the diagnosis of early small-bowel mucosal disease in patients with this disease. VCE detects early lesions in the small bowel of patients with Crohn's disease and is effective in diagnosing patients with suspected Crohn's disease undetected by small-bowel series and enteroclysis [65, 66] and in some cases of Crohn's disease with intestinal strictures missed by enteroclysis. Enteroclysis in patients with Crohn's disease has a diagnostic yield of 37% while capsule endoscopy has a yield of 70%. This is not surprising since enteroclysis will not easily detect flat or mucosal abnormalities [67]. VCE is also superior to CT enteroclysis [5] in patients with known or suspected Crohn's disease, especially in the detection of significantly more inflammatory lesions in the proximal and middle part of the small bowel. VCE probably is less effective than radiology at detecting fistulae, and this might be a reason for sometimes choosing radiological investigations in preference to VCE [68].

There is concern that a capsule might become stuck or impacted against a stricture. In fact, capsule impaction does occur approximately in the 2-5 % of cases. Most capsule impactions are asymptomatic and rarely produce obstructive symptoms. A "patency" capsule has been developed to detect possible strictures noninvasively and more accurately than enteroclysis. This device has the same dimensions as the VCE but has a dissolving body. Use of the patency capsule may be of value to rule out the possibility of intestinal strictures in patients with Crohn's disease and suspected small-bowel obstruction although the patency capsule can also cause transient obstruction.

The major difficulty of VCE is the definition of a gold standard for diagnosis. Crohn's disease produces mucosal inflammation and ulceration of various intensities in different bowel areas. The earliest lesion in Crohn's disease displays tiny mucosal foci of chronic inflammation and, more recently, a focal loss of villi [69]. Another early lesion is aphthoid ulceration. The finding of one or two aphthous ulcers or erosion in patients during capsule endoscopy is common, and it is likely that many of these do not have Crohn's disease [70].

It must be remembered that all ulceration is not indicative of Crohn's disease. Clinically relevant points to keep in mind are the difficulty in differentiating ulcers of Crohn's disease from those of NSAID use and the high prevalence of NSAID-induced ulcers in 71% of NSAID users [71]. Hence, it is critical to evaluate the history of NSAID use in every patient undergoing VCE. In the absence of NSAID use, diagnosis of Crohn's disease was purposed by certain authors on the presence of multiple aphthous or erosive lesions (>10) that were either continuous or seg-mentally distributed [72]. Infections must be excluded by duodenal biopsy, stool microbiology or serolo-gy.

It is known from older studies that the small bowel is affected in Crohn's disease in about one third of cases [73,74]. Newer studies based on VCE show that the small bowel could be involved in approximately 60% of patients with Crohn's disease. This might be kept in mind in case of lack of response in patients treated with drugs released into the terminal ileum or colon [66,68].

Diagnostic costs for Crohn's disease can be very high. This is probably due to the low diagnostic yield of certain diagnostic procedures. VCE has a higher average diagnostic yield than comparative procedures due to imaging clarity and the ability to visualise the entire small bowel [75-77]. Literature review found the average diagnostic yield of small-bowel follow-through (SBFT) and colonoscopy of Crohn's disease to be 53% whereas VCE had a diagnostic yield of 69%. Recent economic analysis comparing VCE with traditional diagnostic procedures demonstrates that employing VCE as a first-line diagnostic procedure appears to be less costly than current common procedures for diagnosing suspected Crohn's disease in the small bowel [77].

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