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State of the Art Wireless Endoscopy n May of 2000, a short paper appeared in the journal Nature describing a new form of gastrointestinal performed with a endoscopy that was miniaturized, camera that was able to transmit swallowable color, high-fidelity images of the gastrointestinal tract to a portable recording device. 1 The article highlighted the ability of the device to image the entire small bowel, a prospect that had been difficult with preexisting endo- technology. The device, known as
     State of the Art  Wireless CapsuleEndoscopy  Douglas G. Adler, MD I Christopher J. Gostout, MD n May of 2000, a short paper appeared in the jour-capsule begins to record images at a rate of 2 per secondnal  Nature describing a new form of gastrointestinaland transmit them to the belt- pack receiver. Thecapsuleendoscopy that was performed with aminiaturized,continues to record images at this rate over the courseof swallowable camera that was able to transmitcolor,the 7 to 8 hour image acquisition period, yielding atotalhigh-fidelity images of the gastrointestinal tract toaof approximately 50,000 images per examination.The portable recording device.The article highlightedthecapsule’s lens is hemispheric and yields a 140 -degree 1 ability of the device to image the entire small bowel,afield of view, similar to that of a standard endoscope. The prospect that had been difficult with preexistingendo-capsule is disposable and does not need to be recoveredscopic technology. The device, known as the M2AImag- by the patient or medical personnel.ing System (Given Imaging, Atlanta, GA), quicklygen- Receiver/Recorder Unit erated widespread interest within thegastrointestinalcommunity as a means of investigating small boweldis-In order for the images obtained and transmitted byease. The following year, the device was granted approv-the capsule endoscope to be useful, they must beal by the US Food and Drug Administration for useinreceived and recorded for study. Patientsundergoinghumans, and it is now widely available in theUnitedcapsule endoscopy wear an antenna array consistingof States. At present, the exact role of wireless endoscopyis8 leads that are connected by wires to therecordingstill being defined. Few well-constructed clinicalstudiesunit, worn in standard locations over the abdomen,ashave been performed to date to formally assess theindi-dictated by a template for lead placement( Figure2 ).cations, sensitivity, specificity, and clinical utility of theThe antenna array is very similar in concept and prac-device, but some encouraging data from animalstudiestice to the multiple leads that must be affixed tothehave been published with regard to the ability of thede-chest of patients undergoing standard 12 -leadelectro-vice to successfully locate small bowelabnormalities.cardiography. The antenna ar ray and battery pack can 2 This article reviews the fundamentals of wirelesscapsule be worn under regular clothing. The recordingdeviceendoscopy. Special attention is paid to theindications,to which the leads are attached is capable of recording benefits, and drawbacks of the technique, as well astothe thousands of images transmitted by thecapsulethe strengths and limitations of clinical data availabletoand received by the antenna array. Ambulatory (non-date.vigorous) patient movement does not interferewithimage acquisition and recording. A typical capsule en- THE CAPSULE ENDOSCOPYSYSTEM doscopy examination takes approximately 7hours.The capsule endoscopy system is composed of several Computer Workstation key parts: the capsule itself, a portable image receiver/recorder unit and batter y pack, and a specially modifiedOnce the patient has completed theendoscopycomputer workstation.examination, the antenna array and imagerecordingdevice are retur ned to the health care provider.The Wireless Endoscopy Capsule recording device is then attached to a specially modifiedThe imaging capsule is 11 mm by 26 mm, is pill-computer workstation, and the entire examinationisshaped, and contains these miniaturized elements: a bat-downloaded into the computer, where it becomesavail-tery, a lens, 4 light-emitting diodes, and anantenna/able to the physician as a digital video. Theworkstationtransmitter ( Figure1 ). The capsule is sealed and resistant (continued on page 17) to decay within the gut. The capsule comes fromthemanufacturer ready to use and is activated onremoval  Dr. Adler is an Advanced Endoscopy Fellow and Dr. Gostout is a Pro- from a holding assembly, which contains a magnetthat  fessor of Medicine, Department of Internal Medicine, Division of Gastro- keeps the capsule inactive until use. Once activated,the enterology and Hepatology, Mayo Clinic, Rochester, MN. 14 HospitalPhysician  May 2003 www.turner-white.com     Adler & Gostout : Wireless Capsule Endoscopy : pp. 14 – 22 (from page 14) Figure2. The 8-lead antenna array, which receivesimages Figure1. The imagingcapsule.transmitted from the capsule endoscope and transfersthemto the image recorder. software allows the viewer to watch the video atvaryingrates of speed, to view it in both forward andreversedirections, and to capture and label individual frames aswell as brief video clips. Images showing normalanato-my or pathologic findings can be closely examinedinfull color. A recent addition to the software package isafeature that allows some degree of localization of thecapsule within the abdomen and correlation tothevideo images. Another new addition to thesoftware package automatically highlights capsule imagesthatcorrelate with the existence of suspected blood or redareas. THE CAPSULE ENDOSCOPYPROCEDURE A typical capsule endoscopic procedure begins withthe patient fasting after midnight on the day beforethe examination. No formal bowel preparation isre- Figure 3. The belt and shoulder strap assembly for the image quired; however, a surfactant (eg, simethicone) may be receiver/recorder unit and battery pack. administered prior to the examination toenhanceviewing. After a careful medical examination, the pa-tient is fitted with the antenna ar ray and imagere-antenna array and recording device to the physician.Itcorder. The recording device and its battery pack areshould be noted that gastrointestinal motility isvariablewor n on a special belt that allows the patient tomoveamong individuals, and hyper - and hypomotilitystatesfreely ( Figure3 ). A fully charged capsule isremovedaffect the free-floating capsule’s transit rate throughthefrom its holder; once the indicator lights on thecap-gut. Download of the data in the recording device tothesule and recorder show that data is beingtransmittedworkstation takes approximately 2.5 to 3hours.In- 3 and received, the capsule is swallowed with a smallterpretation of the study takes approximately 1hour.amount of water. At this point, the patient is freetoIndividual frames and video clips of normal or patholog-move about. Patients should avoid ingestinganythingic findings can be saved and exported as electronic filesother than clear liquids for approximately 2 hoursafter for incorporation into procedure reports or patientcapsule ingestion (although medications can betakenrecords. Figure4 shows some examples of images col-with water). Patients can eat foodapproximatelylected during capsule endoscopy.4 hours after they swallow the capsule withoutinterfer- PROS AND CONS OF CAPSULEENDOSCOPY ing with theexamination.Seven to 8 hours after ingestion, the examinationcanThe idea of a capsule wireless endoscope generated be considered complete, and the patient can returnthea great deal of interest and enthusiasm withinthe 17 www.turner-white.comHospitalPhysician  May 2003     Adler & Gostout : Wireless Capsule Endoscopy : pp. 14 – 22 AC Figure4. Images obtained by wireless capsuleendoscopy.( A ) Normal small bowel mucosa. Note resolution of individ-ual villi.( B ) Small bowel angiectasia. ( C ) Edematous small bowel with a large ulcer visible. B gastroenterology community when it was firstmadesmall bowel can be evaluated in this manner.Sondeavailable. The capsule offered clinicians a way to visual-enteroscopy, a means to evaluate the entire small bowelize the entire small bowel, a region that was previouslyendoscopically, is not performed currently for a varietydifficult to view at all, let alone completely.Standardof technical and patient -related reasons.gastroscopes can pass no farther than the secondor The need to image the entire small bowel ischieflythird par t of the duodenum, and pushenteroscopyimportant for patients who have ongoinggastrointesti-(wherein the patient is intubated per os with acolono-nal bleeding from an obscure source and who havehadscope or a specially designed enteroscope) often failsnegative results on standard endoscopicevaluations;to survey the small bowel beyond themidjejunum.this problem is encountered frequently in clinical prac-Conversely, colonoscopy allows gastroenterologists totice. Such patients often must proceed to a varietyof view the terminal ileum when entered in aretrogradeincreasingly invasive investigations, includingsmallfashion from the cecum, but usually less than 20 cmof  bowel radiographs, angiography, tagged er ythrocyte 18 HospitalPhysician  May 2003 www.turner -white.com     Adler & Gostout : Wireless Capsule Endoscopy : pp. 14 – 22 Table1. Indications, Contraindications, andscans, and, occasionally, intraoperative endoscopy in anExperimental Roles for CapsuleEndoscopyeffort to identify the source of  bleeding.Capsule endoscopy, with its ability to visualizethe Indications entire small bowel, seemed ideally suited for the searchfor obscure or occult gastrointestinal bleedingin Occult or obscure gastrointestinal bleeding  patients who had undergone an inconclusivestandard Chronic gastrointestinal blood loss evaluation. The capsule has the ability to obtainhigh- Recurrent overt bleeding in patients with negative resultsof  resolution images of the small bowel mucosa in arela- endoscopicexaminations tively noninvasive manner with minimal patient prepa- Contraindications ration and discomfort. Known or suspected obstruction or stricture There are, however, several significant downsides to Cardiac pacemakers capsule endoscopy. First and foremost, the devicehas Implanted defibrillators no therapeutic capabilities. Any lesion discoveredviacapsule endoscopy that merits treatment must befur- Implanted electromechanicaldevices ther investigated (eg, biopsied) or intervenedupon Pregnancy with standard medical, endoscopic, radiologic, or surgi- Zenker’sdiverticulum cal techniques. This is true whether the lesion is atu- Intestinal pseudo-obstruction mor, a vascular malformation, or a bleeding ulcer.In Motility disorders addition, whereas standard endoscopes have theability Experimentalindications to insufflate air to distend the bowel (greatlyenhanc-ing mucosal visualization), the wireless capsuleviews Inflammator y bowel disease the bowel in a functioning, semicollapsed state;this Small boweltransplantation increases the percentage of bowel that is notimaged Celiac disease even as the capsule passes through it. Thecapsule Chronic diarrhea of unclear cause images are villus-based, which are magnified and sig-nificantly different from the standard videoendoscopicimages to which most gastroenterologists areaccus-tomed. This presents some challenges in theinterpre- CLINICALAPPLICATIONS tation of findings, because practitioners must learnto GastrointestinalBleeding visualize the bowel in a new way. In addition,gastroin-testinal motility varies widely in the general population. Studies evaluating capsule endoscopy alone. CapsuleAlthough, in most patients, the capsule endoscopesuc-endoscopy has been most widely used in patientswithcessfully passes through the entire small bowel beforechronic gastrointestinal blood loss of unclear srcininits batter y is exhausted, some patients experiencecap-whom standard investigations have not beendiagnostic.sule battery depletion while the device is still intheOver the past year, a large amount of data has becomesmall bowel or, rarely, in thestomach.available with regard to the outcome of patients inthisAnother drawback to capsule endoscopy is the risk of situation who under went capsuleendoscopy.the capsule becoming impacted in a region of strictur-Scapa and colleaguespublished an uncontrolled,ret- 4 ing (eg, due to inflammatory bowel disease, surgicalrospective series of 35 patients who underwentcapsuleadhesions, malignancy) and possibly causing a bowelendoscopy for unexplained gastrointestinal bleedinginobstruction. Finally, it is often difficult to discernthewhom there was a suspicion of small bowel disease.Allexact anatomic location of visualized lesions owingto patients had undergone small bowel radiographyandthe fact that the small bowel looks fairly similar through-some patients had undergone a variety of upper andout its considerable length. A physician reviewing acap-lower endoscopic procedures, all with negative or incon-sule endoscopy study often must guess whether alesionclusive results. Capsule endoscopy identified abnormalis in the duodenum, jejunum, or ileum. Temporalcluesfindings in 29 of 35 patients (83%). The mostcommon(such as recent passage through the pylorus for lesionslesions seen were ulcers, with erosions and angiodysplasiaof the duodenum) are helpful but far fromspecific.also being very frequently discovered. Amongthese Newer software packages contain a localization feature29 patients, a definitive source of bleeding was thoughttoto assist in assessing the location of specific lesionswithinhave been discovered in 22 of them(79%).the bowel. Table1 lists indications andcontraindicationsOne of the largest studies presented so far describedto capsule endoscopy.the results of capsule endoscopy in 66 patientswith 19 www.turner-white.comHospitalPhysician  May 2003
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