Diagnostic Imaging
March 2004

OVERREAD

CT localizes lesions found with capsule endoscopy

Combining technologies facilitates diagnoses that conventional imaging struggles to accomplish

By: H.A. Abella

Capsule endoscopy, the camera pill approved by the FDA in 2001, is hampered by its inability to show precisely where the lesions it finds are located. Adding CT scanning to the pill-based imaging strategy may overcome that limitation.

Physicians cannot control the pill once it is ingested, which limits its ability to localize a finding or determine its clinical importance. Combining CE with CT may unleash its full potential, according to researchers at the Mayo Clinic in Scottsdale, AZ.

"If a tumor or mass is detected at capsule endoscopy, CT could be done to localize the mass and evaluate for metastases," said principal investigator Dr. Amy K. Hara, an assistant professor of radiology at the Mayo Clinic.

CT can also be used to evaluate small-bowel obstruction or disease outside the GI tract prior to administering the capsule. Depending on the clinical situation, CT could be performed either before or after capsule endoscopy to provide additional information, Hara said.

"The information we are gaining from CE will allow us to improve our use of CT for better diagnoses and determine when to pair the two technologies," she said.

Hara and colleagues retrospectively compared capsule endoscopy, barium, and CT findings from 52 patients who underwent examination between September 2001 and April 2002. Their study, which confirmed that CE detected more bowel disease than barium or CT, was published in the January issue of Radiology.

CE showed 55% of positive findings, compared with 3% for barium, and 63% of small-bowel findings, compared with 21% for CT. Neither barium nor CT detected angioectasia, the most common CE finding.

CE could have a significant impact on patients with Crohn's disease, tumors, ulcers, vascular malformations, and other small-bowel abnormalities, Hara said. It offers a more comfortable alternative to barium in the evaluation of obscure GI bleeds, and it provides more coverage than standard endoscopy, which reaches only the upper and lowest portion of the small intestine.

CE is less expensive than CT but is still pricey compared with barium studies. It also takes considerably longer to perform than either barium or CT. With CE, however, patients can leave the hospital and go about their business during the exam.

Although the procedure is in the hands of gastroenterologists, closer collaboration with radiologists is expected. The technique will allow physicians to more closely investigate areas that are harder to reach with conventional endoscopy or harder to interpret with CT, said Dr. Mukesh G. Harisinghani, an assistant professor of abdominal imaging and intervention at Massachusetts General Hospital.

CT excels in observation of the bowel's external wall, while capsule endoscopy is extremely effective on the internal wall. This makes them good complementary techniques, Harisinghani said.