Investigation

Investigation

The diagnosis of acute appendicitis is essentially clinical; however, a decision to operate based on clinical suspicion alone can lead to the removal of a normal appendix in 15–30% of cases. The premise that it is better to remove a normal appen dix than to delay diagnosis does not stand up to close scrutiny , particularly in the elderly . A number of clinical and laboratory- based scoring systems have been devised to assist diagnosis. The most widely used is the Alvarado score ( Table 76.2 scor e of 7 or more is strongly predictive of acute appendicitis. In patients with an equivocal score (5 or 6), abdominal ultrasonography or contrast-enhanced CT examination fur ther reduces the rate of negative appendicectomy . Abdominal ultrasonography is more useful in children and thin adults ticularly if gynaecological pathology is suspected, with a nostic accuracy in excess of 90% ( Figure 76.8 ). Modern CT is both sensitive and specific (approximately 95%) in the diagno sis of acute appendicitis ( Figure 76.9 ) and worldwide there has been a steady increase in its use for this purpose . CT has been shown to reduce the rate of negative appendicectomy without an associated increased perforation ra te (due to delay in diag nosis) and may be cost-e ff ective as a result of shorter hospital stay . While the diagnostic accuracy of modern CT scanning for appendicitis is well established, radiation exposure and the theoretical carcinogenic e ff ect ar e a concern. Low-dose proto cols, which reduce the radiation dose to the patient by up to 80%, can be as reliable as standard dose scanning and may be more appropriately applied when considering a diagnosis of acute appendicitis, particularly in the younger adult. Contrast-enhanced standar d dose CT is especially useful in patients in whom there is diagnostic uncertainty , particularly older patients, where acute diverticulitis, intestinal obstruction and neoplasm are likely di ff erential diagnoses.