The current and future clinical applications of capsule endoscopy

摘要

Capsule endoscopy (CE) has become an increasingly popular modality in facilitating the diagnosis of gastrointestinal tract pathologies that are beyond the reach of conventional endoscopy in the recent decades. Largely attributed to the lack of control of the capsule movement, most commercially available CEs are for diagnostic purposes at present. Yet, with the advancement in the capsule design and emerging technologies that allow for the manipulation and guidance of movement of the CE, it is anticipated that the roles of this medical device will be further expanded (Fig. 1). Capsule endoscopy (CE), also known as wireless capsule endoscopy or video capsule endoscopy, was first developed around 20 years ago to facilitate the optical examination of the gastrointestinal (GI) tract. A typical CE system consists of a wireless pill capsule (with a camera and a battery), a data recorder and a sensor that is connected to the data recorder. The images are then transferred to the computer for interpretation. Therefore, CE allows for the direct visualization of the GI tract. It was originally conceived as a minimally invasive tool for examination of the small intestine, which is challenging to reach by conventional endoscopy. The use of CE has been approved by the United States Food and Drug Administration (FDA) since 2001.1 Over the years, rapid developments in CE with a more compact design and longer battery life, has expanded the role of this tool for the examination of the esophagus, the stomach and the colon as well. The most commonly used CE nowadays include PillCam® SB 3 (small bowel), ESO 3 (esophageal), COLON 2 (Medtronic Plc., Minneapolis, MN, United States - formerly Given Imaging Ltd), CapsoCam® SV-2 (CapsoVision Inc., CA, United States), MiroCam® v2 (IntroMedic Co. Ltd., Seoul, South Korea), OMOM® (Jinshan Science and Technology Co. Ltd., Chongqing, China), Hitron® (Jinan Nefisa Medical Trade Co., Ltd, Jinan, Shandong, China), and the EndoCapsule® (Olympus Corporation, Tokyo, Japan).2 Most commercially available CEs are for diagnostic purposes at present, mainly due to the limitations in controlling the capsule movement. One specific diagnostic test includes the use of the PillCam™ Patency Capsule (PC) for the assessment of significant small bowel strictures in patients at risk of this condition prior to formal CE.3 Use of PC has been proven to be safe. Main adverse events reported were residual parylene coating (0.97%) and PC induced small bowel obstruction (0.89%). After patency confirmation by PC, CE retention can be reduced to as low as 0.39–0.51%.4, 5 Research has been under way to explore the ability of CE in performing additional diagnostic tests such as intraluminal content sampling and biopsies, and providing a therapeutic angle such as targeted drug delivery, hemostasis etc. One of the astounding leaps in the development of CE is the ability of gastrointestinal fluid acquisition. The significant role of gut microbiome in many diseases has been increasingly recognized. More accurate sampling methods will undoubtedly aid the analysis of the gut microbiome to facilitate more breakthrough discoveries and innovation. The potential of releasing drugs from CE has also been partially realized due to advances that have allowed a finer capsule movement control as well. Herein, we will focus on the current applications and the possible future applicationsof these devices. Although not recommended to replace oesophagogastroduodenoscopy (OGD), CE can be used to diagnose Barrett's esophagus and variceal bleeding if patients cannot tolerate or have contraindications to conventional endoscopy. A meta-analysis utilizing OGD as the reference standard reported that CE has a sensitivity of 77% and specificity of 86%6 for Barrett's. However, the sensitivity of CE in esophageal varices diagnosis and classification are rather suboptimal, at 76% and 64% respectively7 and more studies are required to validate whether this can become a feasi