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State of the Art

Wireless Capsule

EndoscopyDouglas G. Adler, MD

IChristopher 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 second

nalNaturedescribing a new form of

gastrointestinal

and transmit them to the belt- pack receiver. The

capsuleendoscopy that was performed with a

miniaturized,

continues to record images at this rate over the course

ofswallowable camera that was able to transmit

color,

the 7 to 8 hour image acquisition period, yielding a

totalhigh-fidelity images of the gastrointestinal tract to

a

of approximately 50,000 images per examination.

The portable recording device. The article highlighted

the

capsules lens is hemispheric and yields a 140 -degree1

ability of the device to image the entire small bowel,

a

field of view, similar to that of a standard endoscope. The

prospect that had been difficult with preexisting

endo-

capsule is disposable and does not need to be recovered

scopic technology. The device, known as the M2A

Imag-

by the patient or medical

personnel.ing System (Given Imaging, Atlanta, GA), quicklygen- Receiver/Recorder Uniterated widespread interest within the

gastrointestinalcommunity as a means of investigating small bowel

dis-

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 use

in

received and recorded for study. Patients

undergoinghumans, and it is now widely available in the

United

capsule endoscopy wear an antenna array consisting

ofStates. At present, the exact role of wireless endoscopy

is

8 leads that are connected by wires to the

recordingstill being defined. Few well-constructed clinical

studies

unit, worn in standard locations over the abdomen,

ashave been performed to date to formally assess the

indi-

dictated by a template for lead placement

(Figure

2

).

cations, sensitivity, specificity, and clinical utility of

the

The antenna array is very similar in concept and

prac-device, but some encouraging data from animal

studies

tice to the multiple leads that must be affixed to

thehave been published with regard to the ability of the

de-

chest of patients undergoing standard 12 -lead

electro-vice to successfully locate small bowelabnormalities. cardiography. The antenna ar ray and battery packcan

2

This article reviews the fundamentals of wireless

capsule

be worn under regular clothing. The recording

deviceendoscopy. Special attention is paid to theindications,

to which the leads are attached is capable of recording

benefits, and drawbacks of the technique, as well as

to

the thousands of images transmitted by the

capsulethe strengths and limitations of clinical data available

to

and received by the antenna array. Ambulatory (non

-date. vigorous) patient movement does not interfere

withimage acquisition and recording. A typical capsule en-THE CAPSULE ENDOSCOPY

SYSTEMdoscopy examination takes approximately 7

hours.The capsule endoscopy system is composed of severalComputer Workstationkey parts: the capsule itself, a portable image receiver/

recorder unit and batter y pack, and a specially modified Once the patient has completed the

endoscopycomputerworkstation.

examination, the antenna array and imagerecordingdevice are retur ned to the health care provider.

TheWireless 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 examination

isshaped, and contains these miniaturized elements: a

bat-

downloaded into the computer, where it becomes

avail-tery, a lens, 4 light-emitting diodes, and an

antenna/

able to the physician as a digital video. The

workstationtransmitter

(

Figure

1

). The capsule is sealed and resistant(continued on page 17)

to decay within the gut. The capsule comes from

themanufacturer ready to use and is activated on

removalDr. 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,

theenterology and Hepatology, Mayo Clinic, Rochester,

MN.

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Adler & Gostout : Wireless Capsule Endoscopy : pp. 14

22

(from page 14)

Figure

2.

The 8-lead antenna array, which receivesimages

Figure

1.

The imaging

capsule. transmitted from the capsule endoscope and transfersthemto the image recorder.

software allows the viewer to watch the video at

varyingrates of speed, to view it in both forward and

reversedirections, and to capture and label individual frames as

well as brief video clips. Images showing normal

anato-my or pathologic findings can be closely examined

infull color. A recent addition to the software package is

afeature that allows some degree of localization of

thecapsule within the abdomen and correlation to

thevideo images. Another new addition to the

software package automatically highlights capsule images

thatcorrelate with the existence of suspected blood or

redareas.

THE CAPSULE ENDOSCOPY

PROCEDUREA typical capsule endoscopic procedure begins with

the 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

bereceiver/recorder unit and battery

pack.administered prior to the examination to

enhanceviewing. After a careful medical examination, the

pa-tient is fitted with the antenna ar ray and image

re-

antenna array and recording device to the physician.

Itcorder. The recording device and its battery pack are should be noted that gastrointestinal motility is

variablewor n on a special belt that allows the patient to

move

among individuals, and hyper - and hypomotility

statesfreely ( Figure

3

). A fully charged capsule is

removed

affect the free-floating capsules transit rate through

thefrom its holder; once the indicator lights on the

cap-

gut. Download of the data in the recording device to

thesule and recorder show that data is beingtransmitted

workstation takes approximately 2.5 to 3hours.

In-3

and received, the capsule is swallowed with a small terpretation of the study takes approximately 1

hour.amount of water. At this point, the patient is freeto

Individual frames and video clips of normal or patholog-move about. Patients should avoid ingesting

anything

ic findings can be saved and exported as electronic files

other than clear liquids for approximately 2 hours

after

for incorporation into procedure reports or patient

capsule ingestion (although medications can be

taken

records. Figure

4

shows some examples of images col-

with water). Patients can eat food

approximately

lected during capsule endoscopy.

4 hours after they swallow the capsule without

interfer- PROS AND CONS OF CAPSULE

ENDOSCOPYing with the

examination.Seven to 8 hours after ingestion, the examinationcan

The idea of a capsule wireless endoscope generated

be considered complete, and the patient can return

the

a great deal of interest and enthusiasm within

the

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A C

Figure

4.

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 first

made

small bowel can be evaluated in this manner.

Sondeavailable. The capsule offered clinicians a way to visual- enteroscopy, a means to evaluate the entire smallbowelize the entire small bowel, a region that was

previously

endoscopically, is not performed currently for a variety

difficult to view at all, let alone completely.Standard

of technical and patient -related reasons.gastroscopes can pass no farther than the second

or

The need to image the entire small bowel is

chieflythird par t of the duodenum, and push

enteroscopy

important for patients who have ongoing

gastrointesti-(wherein the patient is intubated per os with a

colono-

nal bleeding from an obscure source and who have

hadscope or a specially designed enteroscope) often fails negative results on standard endoscopic

evaluations;to survey the small bowel beyond the

midjejunum.

this problem is encountered frequently in clinical

prac-Conversely, colonoscopy allows gastroenterologists to tice. Such patients often must proceed to a variety

ofview the terminal ileum when entered in aretrograde

increasingly invasive investigations, includingsmallfashion from the cecum, but usually less than 20 cm

of

bowel radiographs, angiography, tagged er ythrocyte

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Table

1.

Indications, Contraindications, andscans, and, occasionally, intraoperative endoscopy in anExperimental Roles for Capsule

Endoscopyeffort to identify the source of

bleeding.Capsule endoscopy, with its ability to visualize

the Indications

entire small bowel, seemed ideally suited for the search

for obscure or occult gastrointestinal bleeding

in

Occult or obscure gastrointestinal

bleeding patients who had undergone an inconclusivestandard

Chronic gastrointestinal blood lossevaluation. The capsule has the ability to obtain

high-Recurrent overt bleeding in patients with negative results

ofresolution images of the small bowel mucosa in a

rela-endoscopic

examinationstively noninvasive manner with minimal patient

prepa-Contraindication

sration and discomfort.Known or suspected obstruction orstricture

There are, however, several significant downsides toCardiac pacemakerscapsule endoscopy. First and foremost, the device

has Implanted defibrillatorsno therapeutic capabilities. Any lesion discovered

viacapsule endoscopy that merits treatment must be

fur-Implanted electromechanical

devicesther investigated (eg, biopsied) or intervened

uponPregnanc

ywith standard medical, endoscopic, radiologic, or surgi-Zenkersdiverticulumcal techniques. This is true whether the lesion is a

tu-Intestinal pseudo-

obstruction

mor, a vascular malformation, or a bleeding ulcer.

In Motility disordersaddition, whereas standard endoscopes have theability Experimental

indicationsto insufflate air to distend the bowel (greatly

enhanc-ing mucosal visualization), the wireless capsule

viewsInflammator y bowel disease

the bowel in a functioning, semicollapsed state;

thisSmall bowel

transplantationincreases the percentage of bowel that is not

imagedCeliac disease

even as the capsule passes through it. The

capsuleChronic diarrhea of unclear

causeimages are villus-based, which are magnified and sig-

nificantly different from the standard videoendoscopic

images to which most gastroenterologists are

accus-tomed. This presents some challenges in the

interpre- CLINICAL

APPLICATIONStation of findings, because practitioners must learn

to Gastrointestinal

Bleedingvisualize the bowel in a new way. In addition,

gastroin-testinal motility varies widely in the general

population.

Studies evaluating capsule endoscopy alone. Capsule

Although, in most patients, the capsule endoscope

suc-

endoscopy has been most widely used in patients

withcessfully passes through the entire small bowelbefore

chronic gastrointestinal blood loss of unclear origininits batter y is exhausted, some patients experience

cap-

whom standard investigations have not been

diagnostic.sule battery depletion while the device is still in

the

Over the past year, a large amount of data has

becomesmall bowel or, rarely, in the

stomach.

available with regard to the outcome of patients in

thisAnother drawback to capsule endoscopy is the risk

of

situation who under went capsule

endoscopy.the capsule becoming impacted in a region of

strictur-

Scapa and colleagues published an uncontrolled,

ret-

4

ing (eg, due to inflammatory bowel disease, surgical rospective series of 35 patients who underwent

capsuleadhesions, malignancy) and possibly causing a

bowel

endoscopy for unexplained gastrointestinal bleeding

inobstruction. Finally, it is often difficult to discern

the

whom 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 a

lesion

clusive results. Capsule endoscopy identified abnormal

is in the duodenum, jejunum, or ileum. Temporal

clues

findings in 29 of 35 patients (83%). The most

common(such as recent passage through the pylorus for

lesions

lesions seen were ulcers, with erosions and angiodysplasia

of the duodenum) are helpful but far from

specific.

also being very frequently discovered. Among

theseNewer software packages contain a localization feature 29 patients, a definitive source of bleeding was thought

toto assist in assessing the location of specific lesions

within

have been discovered in 22 of them

(79%).thebowel.

Table

1

lists indications andcontraindications

One of the largest studies presented so far described

to capsule endoscopy. the results of capsule endoscopy in 66 patients

with

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chronic gastrointestinal blood loss. A source of bleed- angiography, small bowel barium series, and/or scin-5

ing was identified in 39 patients (59%). These

lesions

tigraphy) had been undertaken. Conventional

studieswere predominately angiectasias, tumors, and ulcers. found a source of bleeding in 5 of 32 patients

(15%)Similar data were seen by Pennazio and

colleagues

in a Push enteroscopy found a definitive source of

bleeding

6

multicenter Italian trial of capsule endoscopy for

ob-

in 7 patients (21%) and questionable sites in an

addi-scure gastrointestinal bleeding. In this study, 60patients

tional 3 patients (9%). Capsule endoscopy found ade-in whom results of upper and lower endoscopy

were

finitive source of bleeding in 20 patients (62%)

andnegative under went capsule studies. Capsule

endoscopy

questionable sites in 7 patients (21%)

(

P< 0.05).

Therewas able to locate a source of bleeding in 29

patients

were no complications of push enteroscopy or wireless

(48%); angiectasias were the lesion mostcommonly

endoscopy in thisstudy.identified, followed by ulcers and tumors. A variety

of

Dalvaux and

colleagues

performed a prospective,1 5

similar studies have also been perfor med. In

these

blinded trial comparing capsule endoscopy to push7 12

studies, capsule endoscopy typically led to the discovery enteroscopy in 59 patients who had negative results

onof a suspected or presumed source of bleeding in 50% upper and lower gastrointestinal endoscopies.

Fifty-to 80% of patients, on average. It is unclear how

many

seven patients underwent both push enteroscopy

andof the lesions identified in these studies were the

defini-

capsule endoscopy, and 2 patients under went

pushtive lesions responsible for the bleeding experienced

by

enteroscopy but not capsule endoscopy. Some

patientsthese patients versus lesions that were suspected to

be

had occult blood loss (n = 31), whereas others had

morethe source of bleeding (ie, many patients haveasymp-

overt bleeding (n = 26). Lesions were seen in 43oftomatic angiectasias in the small

bowel).

57 patients undergoing capsule endoscopy and 32

ofAlthough these studies are certainly encouraging

and

57 patients undergoing push enteroscopy. In 27

pa-preliminarily support the use of the capsule endoscope tients, the results were identical; in 26 patients, the

cap-to identify the source of occult bleeding, it must

be

sule detected lesions not seen during push

enteroscopy,stressed that these were for the most part

retrospective,

and in 6 patients, push enteroscopy detected

lesionsuncontrolled trials that, with the exception of the

work

missed by capsule endoscopy. There were no complica-

of Scapa et al, were presented only in abstract form.

In

tions of either procedure. The improvement in

diagnos-

4

addition, data on long -ter m outcomes (eg, rebleeding tic yield with capsule endoscopy was statistically

signifi-rates, complications) are unavailable in most

instances.

cant ( P= 0.001). The authors of this study

concludedCapsule endoscopy versus push enteroscopy.Perhaps that capsule endoscopy found significantly more

lesionsof more clinical value, a smaller number of studies

have

than push enteroscopy, but they were uncertain of

theprospectively compared wireless endoscopy to push devices influence on the clinical outcome of these

pa-enteroscopy in patients with gastrointestinal bleeding.

In

tients

.a recently published pilot study, Lewis andSwain

com- Van Gossum and colleagues performed capsule1 3 16

pared the findings of capsule endoscopy to push

enter-

endoscopy followed by push enteroscopy in 21

patientsoscopy in 20 patients with obscure gastrointestinal

bleed-

who had previously undergone upper and lower

gas-ing, all of whom had negative results on at least 1

upper

trointestinal endoscopy with negative results. In

thisor lower endoscopy or small bowel radiograph (although study, push enteroscopy outperformed capsule endos-

many had undergone multiple procedures in search of

a

copy. A total of 19 lesions were found in 15

patients.cause). A positive finding (ie, angiectasia, fresh blood, (The other 6 patients presumably had negative

resultsulcer, or tumor) was identified during capsule endoscopy by both techniques.) Of the 19 lesions, 10 were seen

byin 11 patients (55%), but in 4 of these patients, only

fresh

both capsule endoscopy and push enteroscopy, 6

wereblood (and not a discrete lesion) was identified. Incon-

only seen during push enteroscopy, and 3 wereseentrast, push enteroscopy resulted in the discovery of

ang-

only via capsule endoscopy. All of the lesions seen

onlyiectasia in 6 patients (30%), and all of thesepatients

with the capsule were in the distal small bowel ortheunderwent successful endoscopic therapy of

these

cecum and beyond reach of the push

enteroscope.lesions. Although these results are encouraging, if

the

Finally, in the previously mentioned Italian

multicen-cases in which the capsule only visualized fresh blood

are

ter study by Pennazio et

al,

29 of the 60 patients

under-

6

discounted, capsule endoscopy had a similar rate for dis- went push enteroscopy in addition to capsule

endoscopy.covering lesions (35%) as did push enteroscopy

(30%).

Among the 29 patients who had both procedures

per-Remke and colleagues compared these 2 modali- formed, push enteroscopy detected a source of bleeding1 4

ties in 32 patients in whom a search for a sourceof

in 8 patients (28%), whereas capsule endoscopy detected

bleeding (consisting of upper and lower endoscopy, a source of bleeding in 17 patients (59%)

(

P

hp may03 capsule

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