Acute Abdominal Pain: Diagnostic Impact of Immediate CT Scanning

Abstract

Computed tomography (CT) has revolutionized the management of patients with acute abdominal pain, but its role in the diagnostic process is still not defined. In this issue Dr. Cecilia Stromberg et al. present the results of immediate and indiscriminate CT scanning in all patients with acute abdominal pain at their hospital. The diagnosis on 2222 CT scans was correct in an impressive 96.8% of the cases. Does this support the idea that early CT should be a part of the routine diagnostic workup in all patients with acute abdominal pain? My main objection is that this is a retrospective study, and we do not know how often the CT scan resulted in a change in management. It is therefore not possible to estimate the effects of this policy in terms of an improved outcome for the patients and its cost efficiency compared to ‘‘conventional’’ management. Early CT scanning was compared with ‘‘conventional’’ management in one randomized trial that included 118 patients with acute abdominal pain [1]. At 24 hours the diagnostic accuracy was the same in both groups. The CT scan sped up detection of the more serious diagnoses but also overstated the seriousness of disease more often than conventional management. It is not clear if the more rapid diagnosis had an impact on the final outcome for the patients. Another randomized study included 182 patients with suspicion of appendicitis [2]. There was no difference in the outcome between the groups, but the operation was significantly delayed in the CT group. In addition to these randomized trials, there are a large number of nonrandomized studies with contradictory results. A less known property of diagnostic tests is that the predictive values are dependent on the prevalence of disease. A CT scan for appendicitis, the most common differential diagnosis for acute abdominal pain, can attain sensitivity and specificity of about 95% in the hands of an experienced radiologist. Even with this accuracy, however, a CT scan is falsely positive or falsely negative in 32% when the prevalence of disease is 10% or 90%, respectively. Appendiceal CT scanning is therefore not recommended as a ‘‘screening’’ instrument in unselected patients with a low probability of appendicitis or for confirming the diagnosis of appendicitis in patients with a high probability of appendicitis [3]. This caution should be applied for other diagnoses as well. Clinical assessment, supported by laboratory examinations and eventual reassessment after a short period of inhospital observation, is often sufficient to make the diagnosis in patients with typical symptoms and signs and to rule out a serious disease in the large group of patients with spontaneously resolving nonspecific abdominal pain. In these situations, a CT scan without a specific question seldom contributes any useful information. It does, however, increase the cost and add exposure to ionizing radiation; and it may lead to incidental findings that eventually turn out to be of no clinical significance—socalled VOMIT (victims of modern imaging techniques) [4]. It causes unnecessary worry and demands new examinations that increase the costs even further. The indiscriminate use of CT scans may also be the cause of an increasing incidence of appendicitis in the United States; that is, this policy may lead to unnecessary operations for diseases that would otherwise resolve undetected [5]. There is a risk that indiscriminate use of CT will lead to impaired diagnostic skills and that diagnostic techniques will be increasingly prescribed by surgeons to cover up this R. E. Andersson (&) Department of Surgery, County Hospital Ryhov, Jonkoping, Sweden e-mail: rollanders@yahoo.com