Retained surgical bodies (RSB) are any foreign tools left in the patient after the operation. Generally, for this reason, a further procedure is necessary. The presence of RSB may manifest immediately after the operation or after weeks, months or even years. Reinterventions reach 35% mortality, in addition to significant medical and legal costs. Nowadays, the equipment is arranged in such a way so as to recreate a safe environment for both the patient and the physicians, even if this can not prevent human errors. . This device is a new low-cost system able to detect the presence of any surgical sponge to prevent all the consequences of the presence of a foreign body inside the patient. The system is able to work only if the sponge is ad hoc equipped with radio frequency system.