Patients hospitalized with gallstones are at higher risk of developing lethal bile-duct tumors than the general population, but that risk gradually returns to normal levels after gallbladder-removal surgery, researchers report in the British Journal of Cancer. Cholangiocarcinomas are malignancies of the bile duct, the tube that connects the liver and gallbladder to the small intestine. Tumors originating inside the liver have nearly tripled during the past decade.

National registries in Sweden were used to track 192,960 patients hospitalized for gallstones and 345,251 who underwent cholecystectomy, or gallbladder removal, between 1965 and 2008. Approximately two-thirds were women.

Gallstone patients developed 241 cholangiocarcinoma tumors during 6.4 years of follow-up, while cholecystectomy patients developed 325 cholangiocarcinomas over 12 years. Of the tumors in both groups, 30% were located inside the liver; 70% outside the liver.

Compared with the general population, risk of both tumor types in gallstone patients was three times as high in men and 2.5 times as high in women, and remained high after 10 years, the study found.

In patients who underwent cholecystectomy, tumor risk was about 38% higher than the general population but slowly declined over 10 years. Researchers suggested that gallstones might triggerchronic inflammation, a mechanismunderlying several cancers.

Caveat: As many gallstone patients have no symptoms, it is possible study patients had more severe gallstone disease, making it difficult to generalize the results to the average individual with gallstones, researchers said.