NATIONAL HARBOR, MD. – Endoscopists using the water-infusion method of screening colonoscopy found significantly more adenomas if they added indigo dye, compared with the water method alone, a new study has shown.
"Indigo carmine enhances any surface irregularities" when used as part of screening colonoscopies, Dr. Joseph W. Leung said in a late-breaking abstract session at the annual meeting of the American College of Gastroenterology.
Indigo carmine is used to enhance adenoma detection in chromoendoscopy, which is a more cumbersome process than the water method, Dr. Leung said. He and his colleagues conducted a randomized, controlled trial to assess the value of adding indigo carmine to the water method. The protocol was to add 10 mL 0.8% indigo carmine per 1 liter of water (0.008% indigo carmine).
A total of 84 patients were randomized to screening colonoscopies via the water method alone, and another 84 were randomized to the water method with indigo carmine. The mean age of the patients was 58 years, and more than 75% of patients in each group were men. Body mass index and family history of colon cancer were similar in the two groups, but the indigo carmine group included significantly more smokers than the water-method-only group.
Overall, the adenoma detection rate was 62% in the water-plus-indigo carmine group, compared with 44% in the water-only group, and this difference was statistically significant (P = .03). One cancer was detected in each group.
The colonoscopies were performed by two endoscopists who had experience with both methods, noted Dr. Leung of the Sacramento VA Medical Center in Mather, Calif. Patients were blinded as to which procedure they had, and all patients underwent intravenous conscious sedation.
In both groups, air was suctioned out of the rectum when a high-resolution colonoscope was inserted. Water was infused, and any residual stool or cloudiness was suctioned out, followed by another infusion of clear water. "Water infusion and suction was done in rapid sequence," Dr. Leung said.
"Upon seeing the appendix opening under water, water was suctioned and air was insufflated to facilitate inspection on scope withdrawal," he added.
Dr. Leung offered several possible explanations for the increased adenoma detection rate when indigo carmine was added to the water method.
"The water exchange minimizes residual water and allows undistracted examination during withdrawal," he said. The addition of indigo carmine dye enhances the contrast between a lesion and the surrounding mucosa, which improves polyp detection, he noted. Also, the water method offers improved visualization, and the warm water may reduce spasm in the colon, he added.
The study was supported in part by clinical research grants from the American Society for Gastrointestinal Endoscopy and the American College of Gastroenterology. Dr. Leung had no personal financial disclosures.