LOS ANGELES — Virtual colonoscopy missed adenomatous lesions in 12% of patients, including 5% who had advanced lesions detected only on a follow-up optical colonoscopy, researchers reported at the annual Digestive Disease Week.
Investigators at the University of Wisconsin, Madison, studied records of 160 patients who first had virtual colonoscopy performed by primary 3-D read with 2-D resolution and were then sent for optical colonoscopy.
Patients had both tests if a significant portion of the colon was not visualized on virtual colonoscopy, if they had findings of a polyp or mass greater than 10 mm, if virtual colonoscopy detected polyps between 6 mm and 9 mm, or at the patient's discretion. Lesions less than 6 mm that were seen on virtual colonoscopy were not reported, and patients with these lesions were not referred for optical colonoscopy.
Invasive colonoscopy detected adenomatous lesions not seen on virtual colonoscopy in 19 of 160 patients. Eight of these patients had previously undetected advanced lesions, defined as any adenoma greater than 9 mm or a lesion less than 9 mm with villous pathology.
The second test also detected a false-positive rate of 5% with virtual colonoscopy.
In all, conventional colonoscopy detected 138 lesions, in 54 patients, that had not been seen on virtual colonoscopy, including 99 less than 6 mm, 27 between 6 mm and 9mm, and 12 greater than 9 mm. Most of the lesions were hyperplastic.
“These findings suggest that virtual colonoscopy identifies the majority of colorectal polyps with advanced pathology during routine screening examinations,” said Dr. Daniel Cornett of the section of gastroenterology and hepatology at the University of Wisconsin, Madison.
But he added that virtual colonoscopy poses a “small risk” of missing polyps with advanced pathology, “especially smaller polyps less than 9 mm in size with villous pathology and larger adenomas that are flat in nature or resemble a mucosal fold.”
Both Dr. Cornett and coauthor Dr. Courtney Barancin, a gastroenterology fellow, expressed concern that some protocols for virtual colonoscopy do not refer for optical colonoscopy patients with lesions less than 6 mm.