People with gallstones appear to be at increased risk for colon tumors called adenomas, which frequently develop into cancer over time if they are not removed, findings published in the American Journal of Gastroenterology indicate.

Many studies “have reported a moderately increased risk of colorectal cancer in patients” who’ve undergone gallbladder removal, note Dr. Yutaka Yamaji, of the University of Tokyo, Japan, and colleagues write. “In contrast, few reports have been published regarding colorectal adenoma.”

Moreover, they note, “very few studies have investigated the association between (gallstones that have not been removed) and colorectal adenoma, but data indicate that the two are not related.”

The researchers therefore examined the association between gallstones and colorectal adenoma in 44,58 subjects who underwent ultrasound, to look for gallstones, and colonoscopy, to look for colorectal adenomas. The subjects also completed a questionnaire on lifestyle habits.

Overall, 4189 subjects had normal gallbladders while gallstones were detected in 206 subjects and 63 underwent gallbladder removal.

The rate of colorectal adenoma was 29.6 percent in gallstone patients, significantly higher than the 17.7 percent rate in subjects with normal gallbladders. Only 15.9 percent of patients who had their gallbladders removed developed colorectal adenomas, which was not significantly different from patients without gallstones.

On final analysis, gallstones increased the risk of colorectal adenomas by 57 percent.

“We did not detect an association between (gallbladder removal) and colorectal adenoma, but (gallstones with no symptoms) and colorectal adenoma were related,” Yamaji and colleagues note. “Although the mechanism of this association is unclear, it is possible” that the cancer-promoting properties of bile, which gallstones are made of, may play a role.

SOURCE: American Journal of Gastroenterology, November 2008.