14 Wireless Video Capsule Endoscopy
Jodie A. Barkin, Lauren B. Gerson, and Jamie S. Barkin
Video capsule endoscopy (VCE), introduced globally in 2000 and in the United States in 2001, has enabled the gastroenterologist to view the small intestine from the pylorus to the ileocecal valve, territory that usually spans 16 to 20 feet (400–800 cm) in most humans. VCE can be done in the inpatient or outpatient setting. VCE can be swallowed by the patient or, if need be, endoscopically deployed into the duodenum. Small bowel preparation prior to VCE has been shown to improve visualization and diagnostic yield. Previously classified as obscure gastrointestinal bleeding and recently renamed as small bowel bleeding, suspected small bowel bleeding is the most common indication for VCE. VCE is indicated after the patient has undergone adequate esophagogastroduodenoscopy and colonoscopy. VCE may find lesions in up to 60% of patients with obscure gastrointestinal bleeding, and should be performed as close as possible to an obscure overt bleeding event to increase diagnostic yield. Suspicion of small bowel Crohn’s disease or assessment of Crohn’s disease activity is a frequent indication for VCE; however, VCE’s role in patients with stable active Crohn’s disease is unclear. While VCE administration is considered to be generally safe, there is a potential risk of capsule retention, defined as nonpassage of VCE into the cecum within a 2-week period. In patients with suspected small bowel bleeding, retention rates are approximately 1 to 2%, whereas the risk of VCE retention in patients with inflammatory bowel disease may range from 2 to 13%. This chapter will discuss preparation and indications for VCE, available technology, reading techniques, and management of findings.
VCE was approved by the Food and Drug Administration (FDA) in 2001 as an adjunctive aid for diagnosis of small intestinal disorders, and in 2003 as a first-line modality for this indication. Initial VCE devices required the patient to wear aerials secured to the chest and abdomen in order to transmit images by radiofrequency telemetry to a data recorder. While initial capsule technology captured 8 hours of data (approximately 70,000 images), newer batteries now allow for 12 hours of data gathering, ensuring greater completion rates to the cecum. While initial capsules featured a field of view of 140 degrees and now feature mainly 160 degrees, newer capsules are in development that allow for a 360-degree field of view, as it has four cameras located around the center of the capsule (CapsoCam, CapsoVision Inc, Saratoga, California, United States). Whether increased field of view translates to increased diagnostic yield is currently under investigation. All VCE capsules contain light-emitting diodes (LEDs) that allow for emission of light in the otherwise dark small intestine, and feature chips with complementary metal-oxide-semiconductor technology. A newer generation VCE from Korea (MiroCam, IntroMedic, Seoul, Korea) uses the body rather than telemetry to conduct the signal, increasing the operating time (capture rate three frames per second as opposed to two frames per second). An esophageal capsule that is a “double-header” with 2 cameras is able to capture 14 frames per second. Current commercially available VCE systems are compared in ▶Table 14.1. To date, comparative studies between capsule brands have not shown significant differences in diagnostic yields. Use of a second VCE compared to one has been associated with increased rates of small bowel pathologic findings.
The current generation of VCEs has only demonstrated visualization of the papilla in 10% of cases or less. However, a new VCE under development with a 360-degree field of view has increased the ampulla detection rate to approximately 70%. 6 As expected in an exclusively diagnostic modality, VCE is limited by an inability to provide therapeutic capabilities, lack of external control of capsule movement, and potential difficulty in localizing the exact site of a lesion. 7 Newer generations of VCE with possible external control of capsule movement through the small bowel are in development but are not commercially available at this time. 8
14.3 Setting and Preparation for Video Capsule Endoscopy
VCE can be done in the inpatient or outpatient setting, although the latter is generally preferred as gastric and small bowel transit times are improved when patients are ambulatory. In the inpatient setting, particularly if patients are receiving narcotics or other motility-altering medications and are bedridden, placement of the capsule endoscope into the duodenum is recommended using a through-the-scope capsule-loading device that is advanced into the duodenum, and the capsule is released into the second portion of the duodenum, bypassing the stomach. In addition, a vigorous preparation and use of promotility drugs may be beneficial.
Many studies, including a 2009 meta-analysis, have demonstrated that small bowel preparation improves small bowel visualization and diagnostic yield of VCE. 9 The patient should be on a clear liquid diet the day prior to capsule administration. Administration of 2 or 4 L of polyethylene glycol solution on the night prior to testing was shown to increase visualization quality. In patients taking narcotic medications or other medications, i.e., anticholinergics and antihistamines, which are associated with gastroparesis, cessation of these medications 2 to 3 days prior to VCE administration is recommended. An alternative is that the patient can receive either metoclopramide 10 mg three times daily before meals or erythromycin 250 mg every 8 hours for 2 to 3 days prior to VCE administration. However, given the high rate of gastric retention in patients with gastroparesis or narcotic-induced gastroparesis, endoscopic placement is highly recommended.
In patients taking anticoagulants, including warfarin or the novel anticoagulants, no adjustment in dosage of medication is recommended prior to VCE administration; in fact, studying patients on these medications may help to increase diagnostic yield given the potentially increased risk for bleeding. 10 , 11
14.4 VCE Administration
The approximate VCE dimensions are 11 mm × 26 mm or the size of a “large jelly bean,” and most subjects do not have issues swallowing the capsule. In patients who express concern, having the patient to swallow, and not chew, a jellybean can serve as a test of tolerability, particularly in children or adolescents. Albeit rare, if a patient aspirates a capsule, urgent bronchoscopy should be performed for removal. Once successfully administered, some gastroenterology units will keep the patient in observation for an hour with application of the real-time viewer, in order to assure gastric passage. Should the VCE remain in the stomach after 1 hour, prokinetic agents such as metoclopramide 10 mg can be administered prior to discharge. Patients are allowed to ingest clear liquids 2 hours after VCE administration and a light meal 4 hours after administration. Depending on capsule technology, the study is completed within 8 to 12 hours and the data recorder returned and uploaded. Patients are not instructed to watch for signs of capsule passage in the stool, as this is often not reliable. However, in the case of newer capsules (CapsoCam), patients are provided with a hat and wand in order to collect the capsule, which is then sent back to the company for uploading. 1 , 12 Should the VCE appear to not have passed during reading of the video, an abdominal X-ray can be considered within 2 weeks postingestion to assure passage, or sooner if the patient reports abdominal pain.