CT colonography offers number one choice after failed colonoscopy

An Italian investigation suggests virtual colonography is a better follow-up test for failed colonoscopy than a double-contrast barium enema.

Dr. Lapo Sali of the radiodiagnostic section within the department of clinical physiopathology at the University of Florence and colleagues conducted a population-based screening program for colorectal cancer in Tuscany (World J Gastroenterol 2008;14[28]:4499-4504).
 
During the one-year screening process, 43,290 individuals underwent a fecal occult blood test. About 4.3%, or 1882 subjects, were positive. Of those patients, 77.7%, or 1463 patients, underwent colonoscopy. The rest refused.
 
Sali and colleagues found 7.2%, or 65, of the colonoscopies were incomplete, and 42 of these subjects then underwent CTC, which correctly identified two colonic masses and 20 polyps.
 
The data suggest CTC should be the “go to” method after a colonoscopy fails, especially since the process is easier than a double-contrast barium enema.
 
Other researchers have conducted studies on CTC after incomplete colonoscopy, but the studies included asymptomatic as well as symptomatic subjects, according to Sali and colleagues.
 
The results for medium-sized polyps (6 to 9 mm), with a per-lesion positive predictive value of 77.8%, might be due to thinner collimation for CT scanning and double reading of the examinations, the researchers said.
 
In addition to failed colonoscopies, the researchers noticed a high number of false-positive results, which led to unnecessary repeat colonoscopy. They suggest fecal tagging to reduce the number of false positives.
 
Sali’s study is nothing earth-shattering, according to Dr. Judy Yee, vice chair of radiology and biomedical imaging at the University of California, San Francisco, but it confirms the American Cancer Society’s and American College of Radiology’s recommendations from May that CTC is useful for colon cancer screening.
 
“CTC has a couple of advantages over a barium enema,” Yee said. “It’s easier on the patient, and you can view a portion of the colon not seen on barium enema.”
 
Barium is a thick liquid, difficult to administer, and it often won’t coat the colon adequately, Yee said.
 
“Additionally, CTC is shown to be more accurate for identifying polyps,” she said.
 
For more information from the Diagnostic Imaging archives:
 
CT colonography’s proven clinical worth now invites reimbursement
 
Available scanners tackle future CTC screening demand
 
Radiology societies seek Medicare coverage for CT colonography