757 The study group consisted of 50 consecutive patients with segmental or lobar atelectasis of the lung from various causes who had chest radiographs and CT scans performed within Determining the Cause of Pulmonary Atelectasis: A Comparison of Plain Radiography and CT John H. Woodring1 Received October 19, 1987: accepted after re- vision December 22, 1987. Department of Diagnostic Radiology, A. B. Chandler Medical Center, University of Kentucky, 800 Rose St., Lexington, KY 40536-0084. Address reprint requests to J. H. Woodnng. AJR 150:757-763, April 1988 0361 -803X/88/1 504-0757 © American Roentgen Ray Society In a retrospective analysis of 50 patients with segmental or lobar atelectasis of the lung, chest radiographs and CT studies were compared for their abilities to distinguish whether a centrally obstructing tumor was the cause. This was done to help define the role of CT in evaluating patients with atelectasis. Atelectasis was caused by an obstruct- ing tumor in 27 cases and a variety of other conditions in 23. The chest radiograph correctly identified an obstructing tumor as the cause of atelectasis in 24 of 27 patients on the basis of the presence of a central hilar mass or obvious bronchial abnormality; there was 89% sensitivity and 96% specIficity with a 12% false-negative rate and a 4% false-positive rate. CT correctly identified all 27 obstructing carcinomas on the basis of the presence of either a central bronchial abnormality or a central hilar mass; there was 100% sensitivity and 87% specificity with a 0% false-negative rate and a 10% false- positive rate. Absence of air bronchograms or the presence of mucus-filled bronchi within the atelectatic lung were secondary CT findings that also favored the presence of an obstructing tumor. Although the chest radiograph was more specific than CT for tumor as the cause of atelectasis (96% vs 87%, respectively), it was less sensitive than CT for tumor (89% vs 100%, respectively) resulting in missed tumor diagnoses. CT identified all cases caused by obstructing tumor and successfully excluded obstructing tumor in most of the remaining cases, with an acceptable number of false-positive tumor diagnoses (10%). CT should be performed when the cause of segmental or lobar atelectasis cannot be established with certainty on the basis of the chest radiograph. Patients with segmental or lobar atelectasis are frequently encountered in daily radiology practice. In most cases, the cause of atelectasis is apparent from the patient’s history, clinical examination, and chest radiographic findings. However, the accurate assessment of atelectasis caused by an obstructing tumor is still very important in initial radiographic evaluation. Although the plain radiographic and CT manifestations of pulmonary atelectasis are well known, it is unclear how much the radiologist can rely on the plain film to distinguish atelectasis due to obstruction by tumor from atelectasis due to other causes. CT has been reliable in showing endobronchial tumor as a cause of atelectasis [1 ]. However, the sensitivity, specificity, and false-positive and false-negative rates of plain film and CT diagnoses seldom have been addressed, and the role of CT in evaluating patients with atelectasis is uncertain. In this paper, we review the plain film and CT manifestations of segmental and lobar atelectasis in order to assess the accuracy of both techniques in distinguishing obstructing tumor from other causes of atelectasis and to give guidelines for the use of CT in evaluating atelectasis identified on the initial chest radiograph. Materials and Methods Downloaded from www.ajronline.org by 171.243.67.90 on 05/25/23 from IP address 171.243.67.90. Copyright ARRS. For personal use only; all rights reserved
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