Ultrasonography is inexpensive, safe, and widely available. Diagnostic accuracy, reported to range from 71 to 97 percent67, 68. It is highly dependent on operator skill. Ultrasonography is especially useful in women who are pregnant or of childbearing age, and in children. Major advantages to ultrasonography include noninvasiveness, short acquisition time, lack of radiation exposure, and potential for discovering other causes of abdominal pain (e.g., ovarian cysts, ectopic pregnancy, and tubo-ovarian abscess)69. The most useful finding on ultrasonography that is suggestive of appendicitis is an outer appendicular diameter of 6 mm or greater on cross section70. Difficulties with ultrasonography include the fact that a normal appendix must be
