Surgical teams accidentally leave clamps, sponges and other tools inside about 1,500 patients nationwide each year.

The mistakes largely result not from surgeon fatigue, but from the stress arising from emergencies or complications discovered on the operating table, the researchers reported.

The study found that emergency operations are nine times more likely to lead to such mistakes, and operating-room complications requiring a change in procedure are four times more likely.

It also happens more often to fat patients, simply because there is more room inside them to lose equipment, according to the study.

Two-thirds of the mistakes happened even though the equipment was counted before and after the procedure, in keeping with the standard practice.

Most lost objects were sponges, but also included were metal clamps and electrodes. In two cases, 11-inch retractors metal strips were forgotten inside patients. In another operation, four sponges were left inside someone.

The lost objects were usually lodged around the abdomen or hips but sometimes in the chest. They often caused tears, obstructions or infections. Most patients needed additional surgery to remove the object. In other cases, patients were not even aware of the object, and it turned up in later surgery for other problems.

(Agencies)