General Considerations

The first human ingestion of a video capsule endoscope occurred in 1999, and high-quality images from healthy human volunteers were described in 2000. In August 2001, the US Food and Drug Administration (FDA) approved a commercially available capsule for use in the United States. The capsule had been approved for use in Europe earlier that year.

Five video capsules are available for use in the United States. Three of the capsules are used for small bowel visualization, the PillCam SB (Given Imaging, Yokneam, Israel), the EndoCapsule (Olympus Corporation, Allentown, PA), and the MiroCam (IntroMedic Co, Ltd, Seoul, South Korea). Unlike other available capsules that transmit images using ultrahigh frequency band radio telemetry, the MiroCam, uses electric field propagation to transmit the images. A fourth capsule, the PillCam ESO (Given Imaging), is used for visualization of the esophagus. Finally, there is a capsule used for visualization of the colon (PillCam COLON, Given Imaging) that has FDA approval for examination of the colon in patients who have failed colonoscopy.

The small bowel and esophageal capsules are approximately 11 × 26 mm in size, whereas the colon capsule is 11 × 31 mm. The small bowel capsules have fields of view that vary from 145 to 170 degrees. The capsules acquire between two and six frames per second, with battery lives between 8 and 12 hours. The capsules’ resolution allows for visualization of individual villi. The esophageal capsule has cameras at both ends and acquires 18 images per second, with a battery life of 20 minutes. Finally, like the esophageal capsule, the colon capsule has cameras at both ends. It acquires four images per second, with a battery life of about 10 hours. The colon capsule initially records for 5 minutes and then enters a “sleep mode,” reactivating after 2 hours. This is done to maximize colon visualization.

Indications

The indications for small bowel, esophageal, and colonic capsule endoscopy are summarized in Table 34–1.

A. Obscure Gastrointestinal Bleeding

Obscure gastrointestinal bleeding refers to bleeding that persists or recurs, without a source identified after standard endoscopic evaluation with upper endoscopy and colonoscopy. Obscure gastrointestinal hemorrhage can be subdivided into obscure-overt and obscure-occult gastrointestinal bleeding. Patients with obscure-overt gastrointestinal bleeding present with visual evidence of bleeding, such as hematemesis, melena, or hematochezia. Obscure-occult bleeding is manifested by stool that is positive for occult blood, frequently with iron deficiency anemia. Obscure bleeding accounts for approximately 5% of patients with gastrointestinal bleeding, and the source of bleeding is frequently from the small bowel, between the ligament of Treitz and the ileocecal valve.

Common causes of small bowel bleeding include vascular ectasias, small bowel tumors, Crohn disease, and nonsteroidal anti-inflammatory drug (NSAID) enteropathy (Table 34–2; see also Plates 78 and 79). Vascular ectasias are the most common cause of obscure gastrointestinal bleeding, accounting for 30–40% overall, and are responsible for the majority of obscure gastrointestinal bleeds in older patients. Patients between the ages of 30 and 50 are more likely to have a small bowel tumor as the source of their bleeding. Finally, young patients often are found to have an ulcerated Meckel diverticulum as the source, although it should be remembered that bleeding from a Meckel diverticulum may occur at any age.

B. Crohn Disease

In patients with Crohn disease limited to the small bowel, or in those with indeterminate colitis, arriving at a correct diagnosis can be difficult. Capsule endoscopy also can be used in patients with known Crohn disease to assess for small bowel involvement or degree of disease activity. Capsule endoscopy can help diagnose small bowel Crohn disease by providing mucosal detail that is not available radiologically (Plate 80). It also provides the opportunity to visualize areas of the bowel not accessible by standard endoscopy. Because capsule endoscopy has a resolution of 0.1 mm, it is able to detect small, superficial defects, such as aphthous ulcers. It is important to note, however, that not all mucosal ulcerations occur as a result of Crohn disease (Table 34–3). Ten to 23% of normal volunteers who are not taking NSAIDs will have mucosal breaks and other lesions seen on capsule endoscopy, and 50–71% of NSAID users will have evidence of small bowel injury (red spots, erosions, and ulcerations). Therefore, it is important to use capsule endoscopy findings in combination with other clinical information to arrive at the correct diagnosis.

C. Small Bowel Tumors and Polyposis Syndromes

Capsule endoscopy may be able to detect malignant small bowel tumors years before they would be detected by other imaging modalities, potentially increasing the chance to remove them while still localized and small (Plate 81).

Capsule endoscopy can also detect small bowel polyps in patients with hereditary polyposis syndromes. Peutz-Jeghers syndrome and familial adenomatous polyposis (FAP) are two of the hereditary polyposis syndromes that are associated with small bowel polyps and malignancies. Patients with Peutz-Jeghers syndrome form hamartomatous polyps within the gastrointestinal tract, along with mucocutaneous pigmentation. The polyps have a predilection for the small bowel and will develop in more than 90% of patients (Plate 82). Complications from the polyps include gastrointestinal bleeding, anemia, intestinal obstruction, intussusception, and development of cancer. Patients with Peutz-Jeghers syndrome have a 13% lifetime risk of developing small bowel cancer, so surveillance of the small intestine is recommended. Traditionally, patients underwent radiographic imaging with a small bowel series or enteroclysis every 2 years, starting at age 10 years. This approach exposes a patient to significant amounts of ionizing radiation. In addition, radiologic evaluation with small bowel follow-through, computed tomography (CT) enteroclysis, or magnetic resonance enteroclysis lacks sensitivity for detecting small polyps. Push enteroscopy has also been employed, but is only able to visualize a portion of the upper small bowel. Capsule endoscopy on the other hand, is capable of detecting small polyps throughout the small bowel.

D. Celiac Disease

Celiac disease affects up to 0.3–1% of Caucasians. Celiac disease has traditionally been diagnosed by detection of antibodies (eg, antiendomysial and tissue transglutaminase antibodies), followed by endoscopy with biopsies of the small bowel to confirm the diagnosis. Capsule endoscopy has been proposed as a possible alternative to endoscopy for the diagnosis of celiac disease. Capsule endoscopy findings of celiac disease include scalloping, a mosaic mucosal pattern, loss of mucosal folds, visible vessels, and micronodularity (Plates 83 and 84). An advantage of capsule endoscopy is that it allows for visualization of the entire small bowel, and symptom severity in celiac disease is more closely related to the length of small bowel involved and not to the severity of the villous atrophy seen on biopsy.

Capsule endoscopy may have an even more important role in the evaluation of refractory celiac disease. Celiac disease can be complicated by small bowel adenocarcinoma, lymphoma (including enteropathy-associated T-cell lymphoma), and ulcerative jejunitis. In patients who fail to respond to a gluten-free diet or who have a recurrence of symptoms while on a gluten-free diet, further evaluation is needed to differentiate between refractory celiac disease (ie, celiac disease that does not respond to a gluten-free diet), ongoing gluten ingestion (intentional or unintentional), or a complication of celiac disease.

E. Other Applications

Capsule endoscopy has also been used to evaluate for evidence of small bowel graft-versus-host disease in patients following bone marrow transplantation, to look for evidence of rejection following small intestinal transplantation, and to evaluate for radiation enteritis. However, in the case of suspected radiation enteritis, the risk of capsule retention is increased. In addition, capsule endoscopy may detect small intestinal varices or portal hypertensive enteropathy in patients with portal hypertension.

Esophageal capsule endoscopy can be used to detect esophageal varices, erosive esophagitis, and Barrett esophagus. Finally, colon capsule endoscopy is used for colorectal cancer screening.

Contraindications

Capsule endoscopy is contraindicated in some patients. Because cooperation is required, demented patients are not good candidates for capsule endoscopy. Capsule endoscopy is also contraindicated in patients with cardiac pacemakers or defibrillators (due to concerns that the capsule could interfere with the cardiac device) and in pregnant women (due to a lack of data on the effects of capsule endoscopy in pregnancy). Many centers, however, perform capsule endoscopy in patients with pacemakers or defibrillators, and studies suggest that the capsules do not interfere with the devices. In addition, the cardiac devices have not been shown to disrupt the capsule study (with the exception of one instance of images being lost as a capsule passed the pulse generator of an abdominally implanted pacemaker). Finally, there have been no reports of a cardiac device malfunctioning due to a capsule study. Patients should be instructed not to undergo magnetic resonance imaging until passage of the capsule has been confirmed, which can be done with a plain abdominal radiograph if the capsule was not seen to pass in the stool.

Patients with gastrointestinal tract obstructions, strictures, or fistulas (either suspected or demonstrated on imaging studies) should not undergo capsule endoscopy because of an increased risk of capsule retention or obstruction. A patency capsule (Agile Patency Capsule, Given Imaging) is available to confirm small bowel patency in patients with suspected strictures or obstructions. The capsule is a dummy capsule with a transmitter. The patient swallows the capsule, and then after 30 hours a hand-held scanner or a plain abdominal film is used to determine if the capsule is still present in the small bowel. If it is not, then it is safe to proceed with the capsule endoscopy study. Capsules retained due to a stricture or obstruction will begin to dissolve after 30 hours.