Dr. Ana Echarri Piudo
Complejo Hospitalario Universitario de Ferrol
Dr. Vicente Lorenzo-Zúñiga García
Hospital Universitari Germans Trias i Pujol. Badalona
CAPSULE ENDOSCOPY SYSTEM
Capsule endoscopy for the analysis of the small intestine consists of a small device barely 26 mm in length and weighing 3.7 g, which can be ingested easily and that comfortably and painlessly enables the analysis of the small intestine1.
The first capsule endoscopy system developed for the analysis of the small bowel, and the one with the most widespread use, was marketed in the year 2000 by Given Imaging (Yokne’am, Israel), and is known as PillCam SB® capsule endoscopy. In 2007, the Food and Drug Administration (FDA) approved EndoCapsule® (Olympus) for use, and there are other models in China (OMOM®) and in Korea (MiroCam®) (not marketed in Europe) (Table I).
The PillCam is a device the size of a large vitamin pill (26 mm long, 11 mm wide and weighing 3.7 g) that incorporates a small complete video camera with a light source formed by light-emitting diodes (LED), an optic system, an imaging sensor (complementary metal oxide semiconductor [CMOS]), a wireless radiofrequency imaging transmission system (ASIC transmitter) two small batteries located in the body of the capsule that last 8 hours and an antenna; all of which are included inside a plastic biocompatible and unmovable casing. The view angle is 140º, the magnification is 1:8 and the minimum detected size is 0.1 mm3,4.
The LED light flashes several times per second and illuminates the interior intestinal wall through the transparent optical dome. The lighted image passes through the lens, is captured by the sensor that translates it into electrical signals and transfers these signals to the transmitter. The image transmitter transmits two images per second (currently the new PillCam SB obtains 4 images per second), which the CMOS sensor captures, to a series of antennas (so far up to 8) that are placed above the patient’s abdomen that send said images along with the proper control signals to the DataRecorder4,5.
The DataRecorder is an external portable unit that the patient wears around the waist to capture and store images received by the capsule. These images are later downloaded into the RAPID workstation that processes and analyses the images. The portable unit consists of an energy source containing 5 1.2-volt batteries and a 305-gigabyte hard drive to store the images.
The capsule will remain turned off, thanks to a magnetic switch, while it remains in its medium and within close proximity to a magnet situated in the blister pack. As soon as the capsule moves further away from the vicinity of the magnet in the blister, the magnetic switch in the capsule closes and begins to blink, and it begins to take and transmit images. Transmission continues until the battery is used up4-6.
PillCam SB CAPSULE ENDOSCOPY
PillCam SB capsule endoscopy is designed for outpatient examination of the entire length of the small intestine and views the small intestine up to the ileocaecal valve in most patients. The number of images obtained during an 8-hr small intestine capsule endoscopic procedure and stored in the DataRecorder is 56,700. The capsule advances through the digestive tract, propelled by natural peristalsis, until it is naturally expelled by the colon. The actual duration of transit varies
from patient to patient, based on the patient’s
factors, underlying diseases or the presence of motility disorders with an average gastric transit time of 70 minutes and a duodenocaecal transit time that ranges between 90 and 194 minutes7,8.
The images transmitted by the capsule are arranged and labelled in chronological order beginning from the time of activation, which enables the calculation and analysis of the transit times.
The RAPID workstation and its application are used for the processing, storage, interpretation and offline analysis of video data acquired by the capsule endoscopy. The RAPID workstation downloads images captured by the DataRecorder or recorder that are transferred to a standard video format, permitting the processing of images and the extraction of clinically relevant data from the captured images via analytical algorithms. It also permits the viewing, storing and processing of videos and the preparation a PillCam endoscopy report.
The workstation incorporates a series of functions that contribute to reading the examination: automatic brightness control, transit time control, zoom that enables frames to be analysed in detail, position locator, blood indicator, multiview option and a speed bar that allows one to adjust the rate at which frames are of shown.
CAPSULE ENDOSCOPY PROCEDURE
Hospitalization is not needed to perform this technique, and it can be done on an outpatient basis, after 6-8 hours of fasting. Some studies suggest that preparing the small intestine the night before the procedure improves visualisation of the intestinal mucosa and the percentage of capsules that reach the colon before the recording period runs out. Most of these studies use an electrolyte solution based on 2-4 litres of polyethylene glycol, although preparation with sodium phosphate has also been evaluated. The administration of 80 mg of simethicone 20 minutes before the capsule endoscopy is recommended7-9.
Ingesting the capsule
After adjusting the SensorArray® or antennas (8 localization sensors in the anterior abdominal wall) and the DataRecorder (on the waist) to the patient, and after checking the DataRecorder via the RAPID workstation, the patient ingests the capsule, usually standing. The objective is for the capsule to leave the stomach as soon as possible to travel the entire length of the small bowel and thus arrive at the caecum quickly. Some doctors recommend positioning the patient in right lateral decubitus position to facilitate evacuation of the capsule from the stomach. Other professionals use prokinetics to accelerate the travel of the capsule and ensure its arrival at the caecum before PillCam SB’s 8-hour operation time expires.
After this time, when the capsule stops transmitting (and the DataRecorder flashing), the patient returns the system in order for the RAPID video to be downloaded and prepared for review and analysis.
Since our next publication is geared towards the study of inflammatory bowel disease, one must note that, if using the capsule in a patient with known Crohn’s Disease, it is important to rule out the presence of stenosis that could cause retention of the capsule in the small intestine and intestinal obstruction symptoms8-10.
Therefore, it is necessary to perform a proper radiologic test or capsule permeability test that will ensure the conventional use of the capsule.
The resorbable capsule (PATENCY Given Imaging) has been developed to assess the luminal permeability of the gastrointestinal tract before a conventional capsule endoscopy is performed. It has dimensions similar to the regular PillCam, is radiopaque, and has a radiofrequency plate (microchip) in a lactose composition that dissolves in approximately 30 hours if it is kept in the digestive tract, thus allowing it to pass through probable intestinal stenosis. The persistence of the resorbable capsule and the radiofrequency metal are detected by performing an abdominal x-ray or with a manual scanner in the medical office or endoscopy department. With dissolution, the resorbable capsule becomes malleable and is eliminated through the anus.
• The basic and unquestionable indication for capsule endoscopy is the analysis of a digestive haemorrhage that is acute obscure, visible, or chronic occult in origin, when a diagnosis is not achieved after conventional examinations.
• Suspicion of Crohn’s disease with no evidence of lesions in conventional endoscopic and radiologic examinations.
• Suspicion of tumours of the small intestine and the follow-up of patients with polyposis syndromes.
• Suspicion of refractory, malabsorption syndromes (coeliac disease) to rule out intestinal lymphoma.
• Intestinal obstruction or pseudo-obstruction.
• Suspected stenosis in the small intestine. In patients with Crohn’s disease, it is important to rule out the presence of intestinal stenosis by radiologic test or the use of a Patency degradable capsule.
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7. Ladas SD, Triantafyllou K, Spada C, Riccioni ME, Rey JF, Niv Y, et al. European Society of Gastrointestinal Endoscopy (ESGE): Recommendations (2009) on clinical use of video capsule endoscopy to investigate small-bowel, esophageal and colonic diseases. Endoscopy. 2012; 42: 220-7.
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10. Postgate AJ, Burling D, Gupta A, Fitzpatrick A, Fraser C. Safety, reliability and limitations of the given patency capsule in patients at risk of capsule retention: a 3- year technical review. Dig Dis Sci. 2008; 53: 2732-8.