BOSTON (Reuters) - The chance of having an appendix removed unnecessarily has plummeted since 1996 in the United States, possibly because more doctors are using CT scans to confirm appendicitis diagnoses, researchers said on Wednesday. The likelihood of an unnecessary appendectomy went from 24 percent in 1996 down to 3 percent in 2006, according to a team led by Dr. Steven Raman at the University of California, Los Angeles.