Going into surgery to have the left leg amputated and coming out minus the right is usually thought of as the stuff of comic fiction. But it has become common enough in real life for a doctor to recommend printing warning signs on surgical patients before they are wheeled into the operating room. Dr. Harvey D. Cain, an occupational medicine specialist at the Kaiser-Permanente Medical Center in Sacramento, said in a recent letter to the Journal of the American Medical Association that such labeling could help avoid an infrequent but tragic problem -- accidental surgery on wrong body parts. He suggests something like, "Wrong arm. Do not operate." "It's kind of analogous to the signs you see on the freeway: 'Wrong way, do not lenter,'" Cain said. "The principal idea is not to get the wrong side operated on," he said."It's quite practical and I certainly intend to do it on myself if I ever have surgery." The idea is the brainchild of Janet Peyton, a surgical and recovery room assistant at the Kaiser-Permanente facility. Peyton said she thought up the technique last fall after reading a news story of a surgeon who removed the wrong eye from a boy. She and Cain said they have received numerous inquiries about the idea from around the country since the letter was published. Dr. Albert Kahane, head of the surgical committee at Kaiser, says that the idea has been proposed to the committee and is being considered. Peyton says body marking could easily be done as part of the standard pre-surgery procedure. Patients normally are showered before surgery, shaved if necessary, given a shot to make them drowsy, then wheeled to surgery. The surgical sign-painting could be accomplished with an indelible marker after the shower but before the shot, Peyton said. "The patient could help. They kind of like to participate."