Abdominal abscess. II. Diagnostic efficacy of computed tomography and comparison with ultrasonography

In our experience, a combination of Ultrasonographic and computed tomographic examinations is attended by a probability of less than 10% in failing to detect an intraabdominal abscess. Viewed as individual procedures, CT had an overall diagnostic accuracy between 80% and 85%, whereas the accuracy of US was 61%. A positive CT diagnosis denotes a 94% probability that a mass lesion is pressnt in the abdomen while a positive US diagnosis denotes a probability between 81% and 84%. The present patient sample suggests that between 62% and 72% of patients with negative CT diagnoses do not have an abscess, with a corresponding level of confidence of negative US diagnoses being restricted to 46 to 53%. It is to be emphasized that the cata was derived from a rather high risk patient population in which about two-thirds of the cases were found to be localized abscesses or other mass lesions. Patient-related factors are much more likely to render an ultrasonographic examination totally useless than is the case with CT.