Introduction

Capsule endoscopy (CE) has revolutionized many aspects of small bowel imaging and is an important diagnostic procedure in the investigation of obscure gastrointestinal bleeding (OGIB), suspected and known Crohn’s disease, small‐bowel tumors, polyposis syndromes, and celiac disease [1, 2]. Despite its widespread use and expanding indications, there remain no currently validated credentialing guidelines or accreditation process for CE. This discussion will focus upon training to read studies with the capsule endoscopes developed by Medtronic (Dublin, Ireland) and Olympus America Inc. (Center Valley, Pennsylvania, USA). Currently, other available small bowel capsules include MiroCam (Intromedic, Seoul, Korea) and CapsoCam (CapsoVision, California, USA). Available esophageal and colon capsules will be discussed in the following sections.

Description of the capsules

Different types of capsules have been developed to investigate the small bowel, esophagus, and colon. Each is made of biocompatible materials sealed with biocompatible adhesive. The small bowel capsule (Figure 9.1) (PillCam SB3, Medtronic) is cylindrical and measures 11 mm in diameter and 26 mm in length. It has one optical dome with a 156° field of view, and minimum size of detection of about 0.07 mm. White light‐emitting diodes (LEDs) illuminate the bowel wall through the optical dome. The acquired image is focused by a lens on a complementary metal oxide semiconductor (CMOS) camera. The capsule contains silver oxide batteries with a minimum of 8 hours operating time. It captures two images per second and transmits over 50,000 images during a typical exam. Specific to third‐generation PillCam SB capsule is the adaptive frame rate (AFR) feature where the frame rate increases to 6 images per second when the capsule is traveling at a higher rate. An application‐specific integrated circuit (ASIC) transmitter sends the radiofrequency signal to an external data recorder worn by the patient. The upper gastrointestinal capsule (UGI) (Figure 9.2) (PillCam UGI, Medtronic) allows visualization of esophagus and stomach and has replaced prior esophageal capsule. It is larger in size, measures 32 by 11 mm, and has two optical domes with a 172° field of view that capture 35 frames per second during the first 10 minutes and 18 frames per second for the last 80 minutes of the examination. The colon capsule (Figure 9.3) (PillCam Colon 2, Medtronic) is similar in size as the UGI capsule. It has two optical domes, each of which captures 4–35 frames per second with a 172° field of view. It also incorporates the AFR feature, similar to the third‐generation PillCam. In order to facilitate complete imaging of the colon, it shuts down 3 minutes after ingestion and “wakes up” 1 hour and 45 minutes later with at least 10 hours of battery life [3–5].

The capsule endoscopy unit

CE is typically performed in the outpatient setting but may be performed in an endoscopy unit or inpatient setting. There are minimal space requirements to house the equipment, which includes a desktop computer, printer, recording device, interface device between recorder and computer, and data recorder battery charger (Figure 9.4). Once downloaded from the recording device to the workstation, a capsule study may be transferred to a transportable device (DVD, memory key) and read at an off‐site location on a personal laptop on which the reader software has been installed. There is no consensus on whether CE studies must be stored, and each practice should develop its own policy and be consistent.

Once the patient demographic information is entered into the workstation, the data recorder can be initialized. The capsule ingestion may then be performed in any location that has a bed or examination table. The patient lies down to have the leads placed on the abdomen. A razor may be necessary to shave any hair that may impair good adhesion of the leads to the skin. It is most efficient to have a trained nurse or other assistant involved in preparation of the equipment and patient. They may enter the demographic information into the workstation, initialize the data recorder, apply the leads, educate the patient on their activities, and then, at the end of the day, collect the equipment and download the study.

Preparing the patient

Informed consent reviewing the risks, benefits, and alternatives of CE should be obtained in writing prior to administration of the capsule. The two most pertinent risks being the possibility of missed lesions and capsule retention, which may require surgery. As with all endoscopic procedures, it is imperative that a thorough history be obtained. There are few absolute contraindications to CE. Patients with known small bowel obstructions, strictures, or fistulas should be avoided. In patients with known or suspected strictures, patency capsule (PC) has been suggested prior to CE to minimize risk of retention.[1, 2] However, a history of previous bowel obstruction, abdominal surgery, or intestinal resection is not a contraindication to CE. Although the FDA packaging still restricts administration in patients with pacemakers, there are multiple studies proving safety in patients with nondependent cardiac pacemakers and is generally considered safe (See section “Administering the Capsule”). For standard ingestion, patients should be capable of swallowing a pill. In the pediatric population, an attempt at teaching how to swallow a pill should be entertained. A simple strategy has been devised to assess children’s ability to tolerate the swallow by having them practice swallowing with sequentially larger ingestible surrogates. All patients are screened with the “Jelly Bean Test” [6]. Patients start with a mini M&M^®, advance to a TicTac^®, followed by a regular‐sized M&M^®. If they are able to swallow all of these, the child is then asked to practice swallowing with a Brach’s^® jellybean. The 20 × 15 mm Brach’s^® jellybean is comparable to the PillcamSB^® capsule which is 26 × 11 mm (Figure 9.5). Practicing with candies helps alleviate the anxiety patients feel about swallowing the capsule, increasing the likelihood of a successful ingestion. Other specific issues that should be addressed prior to capsule ingestion include swallowing disorders (e.g., achalasia), known Zenker’s diverticulum, gastroparesis, and pregnancy.

Although there are few restrictions prior to the examination, several medications require specific instructions [7]. As this is a noninvasive technique, patients requiring anticoagulants and antiplatelet agents may continue on their standard medications. Many patients with iron‐deficiency anemia will be on iron supplementation. As iron may darken secretions within the small bowel, it may impair interpretation of images (especially within the distal small bowel); as such it should be stopped 3–5 days prior to the procedure. As with any procedure requiring fasting, dosage adjustments may be required with some medications (e.g., oral hypoglycemics, insulin). Patients are instructed to bring their standard medications with them on the morning of the procedure as they may be taken 2 hours after capsule ingestion. As sedatives are not administered, patients do not require an escort. They should wear comfortable clothing. Women are instructed to wear separates and avoid one‐piece dresses. Many patients prefer to have a loose shirt or jacket that can make the belt and data recorder inconspicuous. There are minimal restrictions on activities; however, they should avoid strenuous activities and not undergo an MRI until capsule passage is confirmed.

Unlike standard endoscopic procedures, there is no mechanism of clearing the visual field, which may be impaired by secretions, bubbles, and coating of the capsule by intestinal residue. As such, the efficacy of the examination is highly dependent upon the quality of the bowel preparation. There are variations across centers regarding recommendation on pretest fasting and consumption of clear liquids. While some centers recommend 12 hours of fasting or clear liquids, others recommend 24 hours of clear liquid diet (CLD) or bowel preparation the night prior to testing.

Many recent studies have supported the use of bowel preparation prior to CE. Polyethylene glycol (PEG) has been shown to improve visualization and diagnostic yield during a CE compared to CLD [8]. Several studies have compared volume of PEG (2L vs. 4L) prior to CE and did not find a significant difference in visualization nor diagnostic yield [7–9]. The timing of bowel preparation has been suggested to play a role in CE image quality as “the later the better.” The use of simethicone and other promotility agents has been debated with mixed results. In the most recent clinical practice guideline, consensus group recommended the use of a bowel preparation prior to CE but there was insufficient evidence to recommend a specific type of preparation [2].

The authors prefer a bowel preparation of a CLD the day prior to the procedure along with 2 L of PEG solution the evening prior to capsule ingestion. In addition to bowel preparation, another factor that may affect obtaining complete visualization of the entire small bowel mucosa is incomplete passage of the capsule to the cecum, which may happen in up to 20% of CE cases.

Interestingly, gum chewing may assist in the transit time of the capsule. In a pilot trial [10], patients were instructed to chew one piece of sugarless gum for approximately 30 minutes every 2 hours following capsule ingestion. The percentage of complete capsule passage into the cecum was higher in the chewing‐gum group compared with control (83.0% vs. 71.7%, respectively, p = 0.19). Both gastric transit time and small bowel transit time were significantly shorter in the chewing gum versus control group. Chewing gum may represent an inexpensive and convenient method to increase the likelihood of complete passage of the capsule to the cecum.

The rate of capsule retention appears to be dependent upon the indication for CE (Table 9.1) [11]. Obtaining a good medical history is essential to avoiding capsule retention. CE is contraindicated in patients with known or suspected intestinal obstructions, strictures, or fistulas. Patients with abdominal pain, distension, and nausea or those with known Crohn’s disease should be suspected of having potential for capsule retention. Only 0.75% of patients require intervention for retention of CE [12]. Ideally, however, one would know prior to capsule ingestion if there was a stenotic area that would impede safe capsule passage.

The PillCam Patency Capsule (Medtronic) has been developed to determine bowel patency in patients who have possible strictures (Figure 9.6). It consists of a dissolvable capsule similar size to the PillCam CE that contains a small radiofrequency ID (RFID) tag that can be detected by a handheld scanner and barium, which can be localized by fluoroscopy. There are two timer plugs at each end, which come out 30 hours post ingestion at which time the gastrointestinal secretions enter the capsule and degrade it. The patient is instructed to ingest the capsule (there is no need for any bowel preparation) and return close to but not after 30 hours to evaluate for the persistent presence of the capsule within the intestinal tract. If the scanner indicates that the capsule is still present, an abdominal plain X‐ray is obtained to attempt to isolate the location of the capsule retention (it may merely be still within the colon, indicating safe passage).

Although there is currently no widely accepted means of accurately predicting capsule retention, multiple studies have examined the value of noninvasive imaging studies and PC in predicting capsule retention. One retrospective cohort study included 42 patients undergoing a PC and imaging studies (i.e., MRE, CT) showed similar modest sensitivity and specificity in detecting significant small bowel strictures [13]. Another prospective cohort study included 57 patients undergoing both MRE and PC showed high NPV of MRE in predicting PC retention [14]. Lastly, a recent meta‐analysis showed that retention rates halved in studies that used PC or CT enterography prior to CE supporting the use of radiographic imaging and/or PC in selected populations. Due to previously reported false‐positive rates of PC, it has been suggested that patients with obstructive symptoms to first undergo noninvasive imaging prior to CE. Patients with negative imaging study can proceed to CE while patients with positive imaging study will likely benefit from PC [2].

Administering the capsule

The usual CE exam begins around 8–9 a.m. with capsule ingestion. During the procedure day, patients may return to home, work, or other activities. They should avoid activities such as strenuous exercise, which may cause lead dislodgement. A CLD is generally allowed after 2 hours from capsule ingestion and can be advanced to a light meal after 4 hours. The equipment is removed 8 hours later (correlating with battery length). Some centers allow patients to remove the equipment themselves and return it the following day. If the equipment is to be sent back in the mail, the patient should be instructed to take out insurance covering the full value of the equipment and capsule in case it were to be lost. The patient should be provided a letter, with an emergency contact number, that documents the patient is wearing specialized equipment for a medical examination.

Prior to the ingestion, the patient is outfitted with the procedure‐specific sensor equipment (esophageal or small bowel), which is attached to the abdomen. The data recorder is within a pocket attached to a waist belt or harness.

The small‐bowel capsule endoscope is ingested in the natural way with some water. Very rarely, a patient, despite reporting no previous problems with pill ingestion, may have some initial difficulty swallowing the capsule. It is important to recognize that capsule ingestion should be without coughing or pain. If a patient starts to choke after ingestion, the pill may be within the airway and necessary measures taken (Heimlich maneuver, bronchoscopy). There may be a sensation of pill retention associated with some mild discomfort within the neck or thorax after ingestion. This should be brief and may be mitigated by allowing for additional water ingestion to aid in movement of the pill out of the esophagus. If the symptoms persist, the real‐time viewer can be useful in assuring that the capsule has entered the stomach.

In patients with known anatomic or motility disorders, which may impair capsule ingestion, endoscopy‐guided capsule delivery may be necessary [12]. The mode of placement is based up on the reason for difficulty with capsule ingestion. For those patients with esophageal pathology such as a Zenker’s diverticulum or luminal narrowing, the capsule may be directly delivered with an accessory such as the US Endoscopy (Mentor, Ohio, USA) Roth net or AdvanCE^® device. When attempting placement with the Roth net, one must pay careful attention to avoid trauma during intubation of the esophagus and inadvertent release of the capsule from the net within the oropharynx. The AdvanCE^® device is a catheter‐based system that passes through the endoscope channel. The capsule is placed within a holder that allows for direct placement of the capsule within the small intestine. Releasing the capsule may be difficult if the scope is not in a straight position (Figure 9.7). An overtube may also be used to enable safe passage of the capsule within the esophagus. This approach is limited by the large size of overtube necessary to accommodate the capsule and accessory device (Roth net, snare). In patients with gastroduodenal pathology impeding capsule passage, patients may be allowed to swallow the capsule normally and then immediately undergo endoscopy, where the capsule is retrieved with an accessory device and then directly placed within the duodenum. Most importantly, if endoscopy is necessary to guide capsule placement, every attempt should be made to deliver the capsule to the duodenum and avoid possible gastric retention and subsequent incomplete small bowel evaluation.

Colon capsule endoscopy (CCE) (Figure 9.3) was initially approved by FDA in 2014 for patients receiving incomplete colonoscopy. Subsequently, FDA expanded the indication to include detection of colonic polyps in patients with evidence of lower GI bleeding and patients at high risk of peri‐procedural complications (PillCam COLON 2, Medtronic, CA, USA). PillCam Crohn’s (Medtronic, CA, USA) has been approved and is used in the evaluation of disease activity in both small bowel and colon in patients with Crohn’s disease.

Prior studies examined the efficacy of first‐generation colon capsules (PillCam Colon 1) (CCE‐1) with suboptimal diagnostic characteristics compared with standard colonoscopy. [15–17]. Newer second‐generation colon capsules (PillCam Colon 2) (CCE‐2) have been shown to have improved sensitivity compared to CCE‐1. One prospective, multicenter trial with 117 patients performed head‐to‐head comparison of CCE‐2 with standard colonoscopy showed improvement of sensitivity for polyps greater than 6 mm and 10 mm to be 84% and 88%, respectively [17]. Subsequently, a meta‐analysis assessing the accuracy of CCE in detection of colorectal polyps with studies stratified by CCE‐1 and CCE‐2 confirmed the above findings [15].

Colon capsule requires a more aggressive bowel cleanse to prepare the colon mucosa. In the colon capsule clinical trials, patients are kept on a CLD the day before the examination, administered 3 L of PEG in the evening, and another liter in the early morning of the examination. Additionally, later in the day, they receive two doses of sodium phosphate solution as a “booster” to help propel the capsule through the fluid‐filled colon [4]. Since then, various cleansing and post‐ingestion “boost” regimens have been evaluated in the setting of multiple contraindications to the use of sodium phosphate solution. Several studies have suggested that low‐volume cleansing regimen (2L PEG solution + ascorbic acid) are at least as effective in quality of bowel preparation as standard preparation (4L PEG) with better tolerability [18, 19]. One prospective, multicenter, randomized controlled study compared booster consisting of oral sulfate solution (OSS) and OSS plus diatrizoate solution. All patients received CLD and split dose sulfate‐free PEG‐ELS. Both arms achieved adequate cleansing in 75.9% (study) and 77.3% (control) of patients with higher completion rates in study arm (90.9%) compared with control arm (76.9%) [8]. Ongoing trials will further help establish the appropriate preparation requirements (in the face of most sodium phosphate products being taken off the market) and its utility in colon polyps and cancer detection.

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