New York, Dec 24 (IANS): A combination of factors besides severity of gallbladder symptoms puts a patient at risk of acute gallbladder attacks, thereby necessitating a removal surgery, but researchers found that patients in the highest risk category do not undergo the procedure.

The other significant factors were age, sex, race and associated illnesses.

The new study looked at 11 years of billing records of more than 160,000 patients (66 years and older) who had an initial episode of gallstone trouble.

"Less than a quarter of patients in this study had their gallbladders removed. We sought to determine whether the decision to have the gallbladder removed was actually based on their risk of having gallstone related complications in the next two years," said lead author of the study Taylor Riall, professor of surgery at the University of Texas, Galveston in the US.

The researchers wanted to determine which of these patients were most likely headed for a dangerous gallbladder attack over the course of the next two years.

The patients in the highest risk category should have undergone gallbladder removal surgery.

But the study showed the reverse to be true. Removal of the gallbladder did not seem to depend on risk and those in the most danger had their gallbladders removed least often.

In looking at patients who had the surgery, the study showed risk was not related to removal of the gallbladder.

The risk of developing gallstones increases with age. While a person under 40 has about an eight percent chance of developing gallstones, the risk jumps to more than 50 percent in people 70 years and older.

The study appeared in the Journal of the American College of Surgeons.