Computed Tomography Enterography (CTE) Versus Capsule Endoscopy for Overt, Obscure Gastrointestinal (GI) Bleeding

Up to 5% of patients with recurrent gastrointestinal (GI) bleeding remain undiagnosed by
upper endoscopy and colonoscopy, the presumed source of bleeding in these patients being the
small intestine. These patients fall under the category of "obscure gastrointestinal
bleeding," and frequently require an extensive diagnostic work-up.

Although capsule endoscopy (CE) has a high yield for findings, there are several limitations
to its utility in the care of patients with obscure GI bleeding. For these reasons, most
patients who present with obscure or occult gastrointestinal bleeding typically undergo
various radiologic imaging studies, including enteroclysis, small bowel series, CT scan,
angiography, and radionuclide scan. Recently, many centers (including the Brigham and
Women's Hospital) have begun using CT enterography (CTE) for evaluation of suspected small
bowel pathology. CT enterography combines the improved spatial and temporal resolution of
multidetector row CT with large volumes of an orally administered neutral enteric contrast
material to permit visualization of the small bowel wall and lumen. This modality has been
shown to have considerable advantages over barium small bowel studies by allowing detection
of subtle findings such as mucosal hyper-enhancement or mild wall thickening, and is better
tolerated by patients than CT enteroclysis.

At the Brigham and Women's Hospital, CTE has recently replaced standard abdominal CT when
small bowel pathology is suspected. While CT enterography and capsule endoscopy have been
directly compared in the evaluation of non-stricturing Crohn's Disease, they had not been
directly compared in the evaluation of obscure GI bleeding until recently (see "Pilot Data"
below). The current diagnostic algorithm for obscure gastrointestinal bleeding based on the
American Gastroenterology Association technical review was published in 2007 and does not
include either capsule endoscopy or CT enterography. The videocapsule was approved by the
FDA in 2001 and CT enterography technique has been developed over the last 5 years. Both of
these tests are currently being used as part of standard of care to evaluate obscure
gastrointestinal bleeding in centers where either or both technologies are available,
including the Brigham and Women's Hospital. In addition, patients are also currently being
referred from area hospitals without the capacity for this type of testing to the Brigham
and Women's Hospital for either or both tests for the evaluation of obscure GI bleeding.

Obscure gastrointestinal bleeding (OGIB) refers to bleeding undiagnosed by upper endoscopy
and colonoscopy. In 40-70% of cases of OGIB, a bleeding lesion is localizable to the small
bowel. In OGIB, capsule endoscopy (CE) has a diagnostic yield of 40-80%, and has
demonstrated diagnostic superiority to push enteroscopy, barium studies, angiography, CT
angiography, and routine abdominal CT scan. When CE is non-diagnostic, however, the
subsequent diagnostic algorithm is not well-defined. There is currently no established role
for cross-sectional imaging for this indication. CT enterography (CTE) combines the spatial
and temporal resolution of CT with an orally administered neutral enteric contrast material
that permits detailed visualization of the small bowel. Unlike other imaging modalities such
as nuclear medicine techniques and catheter angiography, CT is less labor-intensive, more
readily available, and provides precise anatomic localization. A novel OGIB-protocol
available at Brigham and Women's Hospital for CTE utilizes a dual-phase, dual energy
technique that obtains images at two time points to better identify active bleeding in the
mesentery. We, the investigators, plan to prospectively study an algorithm that employs CTE
and compare to capsule endoscopy to investigate the effectiveness of both modalities and to
evaluate the potential role of CTE in OGIB.

The goal of our study is to determine observationally the contribution of both CE and the
new protocol for CTE to the evaluation and management of overt obscure GI bleeding and
accordingly revise the clinical algorithm.

We hypothesize that CTE will be as or more effective than CE at identifying culprit lesions
in overt, obscure gastrointestinal bleeding.