Abdominal Imaging
ª Springer Science+Business Media, LLC 2008 Published online: 30 April 2008
Abdom Imaging (2009) 34:149–155 DOI: 10.1007/s00261-008-9404-8
PICTORIAL ESSAY
CT enterography vs. capsule endoscopy Howard S. Boriskin,1 Bethany S. Devito,2 John J. Hines,1 Victor J. Scarmato,1 Barak Friedman1 1 2
Department of Radiology, North Shore University Hospital, 300 Community Drive, Manhasset, NY 11030, USA Department of Gastroenterology, North Shore University Hospital, 300 Community Drive, Manhasset, NY 11030, USA
Abstract Small bowel imaging has been revolutionized by CT enterography and capsule endoscopy. We present an overview of both imaging modalities, discuss advantages and disadvantages of each, and compare findings in Crohn’s disease, occult gastrointestinal bleeding, and small bowel tumors. Both methods complement each other often providing information that the other one cannot. Key words: Enterography—Capsule endoscopy—Small bowel—Crohn’s disease—Gastrointestinal bleeding—Tumor
CT enterography and capsule endoscopy are the two most promising modalities to image the small bowel because of ease of use and high diagnostic yield. We will provide an overview of CT enterography and capsule endoscopy, compare their respective advantages and disadvantages, as well as the imaging findings of both modalities in Crohn’s disease, occult gastrointestinal bleeding, and small bowel tumors. Traditional imaging of the small bowel includes endoscopy, small bowel follow through, enteroclysis, computed tomography (CT), and CT enteroclysis. Each of these traditional modalities has its limitations. There is a limit to how far enteroscopes can be advanced, although recent advances allow complete small bowel evaluation with double push enteroscopy. Double push enteroscopy requires expertise, is more invasive, and is time consuming [1]. Small bowel follow through has been the most commonly used small bowel evaluation in the past, but has a low diagnostic yield [2]. CT with positive oral contrast obscures the bowel wall. Enteroclysis requires expertise, is time consuming, and can be Correspondence to: Howard S. Boriskin; email:
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uncomfortable for the patient. CT enteroclysis, which provides similar information as CT enterography, is uncomfortable for the patient and may not have an advantage if the patient is able to ingest oral contrast in sufficient quantities [3]. Capsule endoscopy is a direct mucosal visualization of the entire small bowel. Therefore, capsule endoscopy is able to image more of the small bowel than traditional endoscopy and has a higher sensitivity for mucosal processes such as ulcers, polyps, and angiodysplasias than fluoroscopic or computer tomographic methods [4]. The capsule is 11 · 26 mm and the battery provides 7–8 h of imaging. The camera has a 140-degree field of view and two images are obtained per second with 1:8 magnification [5]. Images are transmitted via a sensor to a recorder worn on a belt and downloaded onto a computer where the images can be viewed as a continuous video film. The capsule should pass naturally after 48 h [6, 7]. CT enterography uses a neutral (low density) oral contrast agent (VoLumen, E-Z-EM, water, milk, or polyethylene glycol) to achieve small bowel distention followed by a rapid infusion of intravenous contrast to achieve a double contrast examination of the small bowel. Neutral oral contrast permits bowel wall visualization by increasing the contrast between the lumen and the enhanced bowel wall. CT enterography views the entire bowel wall, mesentery, and peri-enteric fat and gives a global overview of the entire abdomen and pelvis. We obtain images using a rapid infusion of nonionic intravenous contrast in both the enteric and portal venous phases or with a single enteric phase. The optimal enteric phase occurs 14 s past peak aortic enhancement [8]. Both modalities also have their disadvantages. Localization of small bowel pathology is limited with capsule endoscopy [9]. The entire small bowel may not be imaged because of rapid transit, failure to reach the cecum, or an increased amount of fluid in the small bowel.
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One of the risks of capsule endoscopy is capsule retention. Capsule retention occurs in 0.7–2% of patients for obscure gastrointestinal bleeding and suspected Crohn’s disease and in up to 8% in patients with established Crohn’s disease [10]. Figure 1A demonstrates a fat suppressed T1 weighted spoiled gradient echo MRI with severe magnetic susceptibility artifact for which the etiology is uncertain. The plain film (Fig. 1B) shows the etiology to be a retained capsule which the patient was unaware did not pass. The patency capsule has been developed as a safe method for determining risk of capsule retention. The patency capsule has the same dimensions as the endoscopy capsule but will disintegrate in 40 h. It has a lactose body with a barium coating and radiofrequency tag inside which can be identified with a scanner [11].
Another disadvantage of capsule endoscopy is the high rate of mucosal breaks or small bowel erosions in healthy people, providing a high false positive rate in diagnosing patients with early Crohn’s disease [12]. CT enterography provides a lower yield than capsule endoscopy in detecting small bowel mucosal lesions [13]. Radiation is a particular concern for Crohn’s patients who may be subjected to numerous CTs. Therefore, we perform CT enterography in Crohn’s patients with a single enteric phase. Another weakness is that CT enterography is limited without intravenous iodinated contrast administration. The sensitivity to detect abscesses, cystic peritoneal metastasis, and appendicitis may be lower than when using a traditional positive oral contrast agent, although this has not been established.
Crohn’s disease Crohn’s disease is an idiopathic, chronic, transmural inflammatory process which can affect any part of the GI tract. The ileocecal area is involved in approximately 50% of patients with only the small bowel affected in 30– 40% of patients [14]. Findings in capsule endoscopy include hyperemia and edema of the involved mucosa, ulcers, strictures, and skip lesions. Figure 2 demonstrates different stages of Crohn’s disease. The first signs of Crohn’s disease involve hyperemia and edema of small bowel mucosa. As the wall becomes more inflamed, it becomes friable and an ulcer forms. As the disease worsens, strictures may develop which can lead to obstructive symptoms. Strictures increase the risk of capsule retention.
Fig. 1. (A) Fat suppressed T1 weighted spoiled gradient echo MR image which demonstrates magnetic susceptibility artifact in the right upper quadrant. (B) The plain film shows the etiology to be a retained endoscopy capsule.
Fig. 2. Crohn’s Disease. (A) The arrows demonstrate hyperemia and edema of the small bowel mucosa which is seen in mild disease. (B) Ulcers form as the wall becomes more inflamed and enlarge as the disease progresses (C). (D) Strictures can develop which can lead to obstructive symptoms.
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Traditionally, CT had been used in the management of extra-enteric complications of Crohn’s diseases such as fistula formation and abscesses, and played a minimal role in identifying small bowel Crohn’s disease. Higher spatial resolution and the capacity to display the enhanced bowel wall with neutral oral contrast in the lumen have made it possible to demonstrate active Crohn’s disease. Findings of CT enterography in Crohn’s disease include segmental mural hyperenhancement, mural stratification, and bowel wall thickening. The degree of mucosal hyperenhancement correlates with the degree of inflammation [15]. CT enterography also demonstrates extra-enteric findings of Crohn’s including inflammation in the peri-enteric fat, engorged vasa recta (Comb sign),
Fig. 4. (A) Arrows demonstrate mural stratification, edema seen in the bowel wall, a sign of active disease. (B) Engorged vasa recta (comb sign). (C) Fibrofatty proliferation. (D) Mucosal hyperenhancement (yellow arrow) and comb sign (red arrow).
fibro fatty proliferation along the mesenteric border of small bowel wall, and fistulas [15]. Figure 3 demonstrates mild Crohn’s disease. Figure 4 demonstrates the different findings of Crohn’s disease on CT enterography. One of the advantages of CT enterography over capsule endoscopy is the identification of complications related to Crohn’s disease such as fistula formation and abscesses. Figures 5 and 6 demonstrate complications of Crohn’s disease. As a noninvasive modality, CT enterography avoids the complication of capsule retention and may also be a reliable radiologic examination in screening for most strictures in patients with suspected Crohn’s disease [16].
GI bleeding
Fig. 3. Axial and coronally reformatted images demonstrate mild hyperenhancement of the mucosa in the terminal ileum indicating a mild terminal ileitis.
Occult gastrointestinal (GI) bleeding is the most frequent indication for capsule endoscopy and is suggested as the next step following negative upper and lower endoscopies [17]. The most common lesions detected are angiodysplasia, inflammatory bowel disease (IBD), and non-IBD related ulcers [4, 18]. Finding the source of GI bleeding with capsule endoscopy can be difficult. Blood obscures visualization of the bowel wall and the camera may not image that small portion of the wall. Figure 7 demonstrates blood in the small bowel lumen. No source for the bleeding was identified in this study. Figure 8 demonstrates an AVM and Fig. 9 demonstrates an ulcer secondary to NSAID use. Differentiating NSAID ulcers from Crohn’s disease can be difficult. Figure 10 demonstrates a CT enterography performed for occult GI bleeding. A large exophytic mass was found off the jejunum which is a pathologically
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Fig. 6. Axial CT image demonstrates an abscess related to Crohn’s disease which appears like other fluid-filled loops of bowel.
Fig. 5. (A) Coronal average intensity projection showing a small bowel to small bowel fistula (red arrow). Numerous sinus tracts are also demonstrated (blue arrows. (B) Sigmoid (red arrow)–ileal (yellow arrow) fistula on a curved multiplanar reformat.
proven gastrointestinal stromal tumor (GIST) tumor. In the setting of acute lower GI bleed, it may be advisable to not wait for the administration of oral contrast. Given the intermittent nature of lower GI bleeding, waiting for the oral contrast may result in a cessation of bleeding. Figure 11 demonstrates a CT performed for GI bleeding without the administration of oral contrast which shows a bleeding Meckel’s diverticulum.
Small bowel tumors Small bowel tumors are rare and often have nonspecific symptoms such as pain, weight loss, and obstruction.
Fig. 7. Capsule endoscopy image which demonstrates blood in the small bowel lumen. In this area of the small bowel, there is too much blood to see the small bowel wall and identify the source of bleeding.
Therefore, the diagnosis is often delayed. The most common small bowel tumors are adenocarcinoma, carcinoid, lymphoma, and gastrointestinal stromal tumors (GIST). Certain appearances suggest different tumors. Adenocarcinoma is usually located in the duodenum. The typical finding is a focal area of small bowel wall thickening which encases the lumen and provides the ‘‘apple core appearance’’ on CT. Primary small bowel carcinoid lesions appear as small, lobulated soft tissue masses. Lymphoma can have many appearances including bowel
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Fig. 8. Circled is an arteriovenous malformation in the small bowel wall.
Fig. 10. Arterial (A) and portal venous phase (B) images from a CT enterography demonstrating a large bleeding exophytic mass off the jejunum which is a pathologically proven GIST tumor. Of incidental note is a left sided IVC.
Figure 12 demonstrates the different appearances of tumors on capsule endoscopy. Figure 12A and B demonstrates a polypoid lesion in the small bowel found to be a GIST tumor. Figure 12C demonstrates an erythematous and eroded small bowel wall proven to be lymphoma. Figure 13 demonstrates a solitary mass at the ligament of Treitz with luminal narrowing characteristic of small bowel adenocarcinoma which is pathologically proven. Figure 14 demonstrates a soft tissue mass in the jejunum which is pathologically proven to be lymphoma. Figure 15 demonstrates an exophytic hyperenhancing mass in the duodenum found to be a GIST tumor. Fig. 9. NSAID ulcer. The small bowel wall has become friable (yellow arrow) with an ulcer beneath (red arrow).
wall thickening or an exophytic mass. Ulceration of the bowel wall can also be seen. Small bowel lymphomas are most commonly found in the ileum. Gastrointestinal stromal tumors can also present as an exophytic mass. GI stromal tumors can be submucosal, subserosal, or intraluminal [19].
Conclusion Capsule endoscopy and CT enterography are revolutionizing evaluation of the small bowel. Capsule endoscopy allows direct visualization of the small bowel mucosa and has a higher sensitivity for mucosal processes. CT enterography provides better visualization of the entire small bowel wall and shows extra-enteric complications of small bowel disease. Disadvantages of
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Fig. 12. Small bowel tumors on capsule endoscopy.( A) and (B) Polypoid lesion in the small bowel seen from different angles. This lesion is a pathologically proven GIST tumor. (C) Erythematous and eroded bowel wall found to be lymphoma.
Fig. 11. Coronal (A) and sagittal (B) CT image reconstruction demonstrating a bleeding Meckel’s diverticulum.
capsule endoscopy include false positives, capsule retention, difficulty in lesion localization, and rapid transit or failure to reach the cecum. Disadvantages of CT enterography include radiation exposure and the need for IV contrast. Capsule endoscopy and CT enterography complement each other often providing information that the other one cannot [20]. References 1. Saurin JC, Delvaux M, Gaudin JL, et al. (2003) Diagnostic value of endoscopic capsule in patients with obscure digestive bleeding: blinded comparison with video push enteroscopy. Endoscopy 35:576–584 2. Hara AK, Leighton JA, Sharma VK, et al. (2004) Small bowel: preliminary comparison of capsule endoscopy with barium study and CT in patients without evidence of small-bowel stricture at barium studies, capsule endoscopy helped to find more small-bowel disease compared with barium examinations and CT. Radiology 230:260–265 3. Wold PB, Fletcher JG, Johnson CD, et al. (2003) Assessment of small bowel Crohn disease: noninvasive peroral CT enterography
Fig. 13. Axial CT image demonstrating an ‘‘apple core’’ lesion at the ligament of Treitz, pathologically proven to be adenocarcinoma.
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Fig. 14. Two coronal CT images demonstrating a soft tissue mass in the jejunum pathologically proven to be lymphoma. Courtesy of Alec Megibow, MD.
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