CHAPTER 5 Small bowel endoscopy
Indications and technique
5.1 Video capsule endoscopy
Key Points
1 Technical principles
Development of the first capsule (Fig. 1) was based on three scientific advances: a CMOS (complementary metal oxide silicone) microchip capable of producing an image comparable with that obtained with a CCD camera; an ASIC (application-specific integrated circuit) system, which allows integration of a small, low-energy video transmitter; and miniature high-power lighting such as an LED (light-emitting diode). These three components are placed in a capsule measuring 1.1 cm × 2.6 cm that can be swallowed. The field of vision obtained is 140°. It is weighted so that it retains its longitudinal orientation for approximately 80% of its intestinal journey, and it passes through the body naturally. The system also comprises a series of sensors which are placed on the surface of the patient’s abdomen and detect signals emitted by the capsule. These are transmitted to a high-frequency tape recorder, contained in a case and worn on a belt by the patient, before transfer to a workstation. The capsule is eliminated in the stools and is a single-use device. This description corresponds to the system developed by Given Imaging Ltd. Since then, the capsule has been improved and is available under the name ‘PillCam SB’, characterized by a wider angle of vision (156°), better resolution (65 536 pixels), and an increased depth of field. The ‘EndoCapsule’, ‘MiRoCam’ and ‘OMOM’ capsules differ in using a CCD rather than CMOS sensor (Fig. 2) to capture images. Studies comparing the ‘Pillcam’ and ‘Endoscapsule’ have not demonstrated any differences in diagnostic yield in patients with obscure gastrointestinal bleeding. The ‘MiroCam’ capsule (Fig. 3) has longer-life batteries (11 h), is smaller in size (11 × 24 mm), has a larger number of pixels (102,400), takes three images per second, and transmits data using conduction through body tissues. This requires constant contact with the mucosa, which may be a limiting factor. Comparative studies with the other two systems are currently underway. The ‘OMOM’ capsule (27.9 mm long, 13 mm diameter, and 6 g weight) is significantly bigger than the others (24–26 × 11 mm and 3.4–3.6 g weight).
3 Safety of VCE and contraindications
To solve the problem of retention, Given Imaging Ltd has developed a calibration capsule, called the ‘M2A Patency Capsule’. If it has not been expelled after 2–3 days, this breaks down spontaneously into small fragments, which easily pass through a narrowed segment. Latest modifications have incorporated two openings at each end of the capsule (the Agile Patency Capsule, Fig. 4), to enhance capsule breakdown. It is important to remember that neither small intestine barium studies nor CT or MR enteroclysis can detect all strictures. It is therefore essential to enquire about the patient’s medical history (complex surgery, use of NSAIDs, radiotherapy of the abdomen, and recent episodes of obstructive symptoms) before carrying out an examination by VCE. The risk of obstruction should be explained clearly before VCE, along with the possibility that a retained capsule may have to be removed endoscopically or surgically. CT or MR enteroclysis or the use of an Agile Patency Capsule is recommended before performing VCE in patients felt to be at risk of small bowel strictures.
4 Indications and results
VCE has already changed the management of patients in the following disorders:
4.1 Chronic obscure gastrointestinal bleeding
This is defined as isolated or recurrent melena, rectal bleeding or iron deficiency anemia with evidence of gastrointestinal bleeding. Patients should have undergone negative upper endoscopy and total colonoscopy before VCE is considered. A positive diagnosis may be found in 55–81% of patients, the yield being higher in those with overt as opposed to obscure bleeding. VCE is superior in detecting lesions responsible for bleeding compared with push enteroscopy (PE), particularly in patients with overt bleeding. Studies have also emphasized the need for examination by VCE as soon as possible after the bleeding episode, the diagnostic yield dropping as time elapses. Finally, the use of a repeat study in patients in whom VCE had initially been negative will yield a diagnosis in a significant number of patients. Two meta-analyses of 14 and 17 studies, respectively, demonstrate that VCE yields a positive diagnosis in 63% of patients compared with 28% for push-enteroscopy. The lesions detected are usually, in decreasing frequency, arteriovenous malformations (Fig. 5), ulceration secondary to NSAIDs, and tumors. When compared with double balloon enteroscopy (DBE), both methods have similar diagnostic yields in obscure gastrointestinal bleeding: 43–60% for DBE and 59–80% for VCE.
4.3 Crohn’s disease
VCE detects more intestinal lesions in patients with Crohn’s disease (Fig. 6) than conventional radiological imaging. The lesions usually detected are mucosal: erosions, purpuric lesions, ulceration, aphthoid lesions, and strictures. Some practical conclusions are shown in Box 1.
Box 1 The role of VCE in Crohn’s disease
4.4 Celiac disease
Some authors have suggested that VCE could be an alternative to endoscopic duodenal biopsies obtained at OGD, particularly in patients unwilling to undergo the procedure, and could be carried out for: chronic iron-deficiency anemia, children with clinical evidence and laboratory results suggesting celiac disease, patients with anti-transglutaminase antibodies, and atypical symptoms in elderly patients (Fig. 7A,B).
Figure 7 (A,B) Celiac disease. (C) Enteropathy associated T-cell lymphoma (EATL) complicating celiac disease.
VCE in combination with DBE is, moreover, the best way of examining patients with celiac disease who have warning symptoms (weight loss, anemia and abdominal pain), while adhering closely a gluten-free diet. VCE is a useful tool for monitoring patients with celiac disease to detect malignant lesions, i.e. adenocarcinoma or lymphoma (Fig. 7C), particularly if ulcerative jejunitis is present.
4.5 NSAID enteropathy
Ulcers, erosions and stenotic diaphragms or webs are usually found (Fig. 8). The clinical significance of minor lesions accompanying the use of NSAIDs is uncertain, as they are also detected in up to 22% of healthy volunteers participating in the control group in studies of NSAID toxicity.
4.6 Detection of intestinal tumors
The frequency of these tumors (Fig. 9) in patients examined by VCE for chronic obscure gastrointestinal bleeding is approximately 6–12%, and 60% of these are malignant. Since the introduction of VCE, it has been noted that the most frequent presentation of these intestinal tumors is chronic obscure bleeding rather than abdominal pain, weight loss or obstruction. This means that VCE has the potential to detect these tumors at an earlier stage.
4.7 Surveillance of familial polyposis
VCE is capable of demonstrating the existence of polyposis (Fig. 10) along the small intestine. Although it may miss duodenal lesions in comparison with PE and DBE, it performs better in the jejunum and ileum. Its use is even more impressive in Peutz–Jeghers syndrome in which it can detect lesions capable of causing intussusception, and demonstrate ulcerated polyps responsible for chronic anemia. Its use is now widely accepted in the surveillance of familial adenomatous polyposis (FAP) associated with duodenal polyps. The same applies in juvenile polyposis. If VCE is used to monitor patients with FAP, it should be kept in mind that it does not detect all lesions in the duodenum, particularly the periampullary region. The duodenum must be investigated by a side-viewing endoscope in these patients. Finally, VCE cannot accurately assess the size of tumors in patients with familial polyposis, and often overestimates this. MR-enteroclysis appears to be better for assessing the size of these lesions.
Box 2 summarizes the role of VCE in small intestinal disorders.