Early pulmonary involvement in ankylosing spondylitis: Assessment with thin-section CT

AIM: To determine the frequency and the distribution of early pulmonary les ions in patients with ankylosing spondylitis (AS) and a normal chest X-ray on thin-section CT and to correlate the CT findings with the results of pul monary function tests and clinical data. MATERIALS AND METHODS: Twenty-five patients with clinically proven AS and n o history of smoking underwent clinical examinations, pulmonary function te sts (PFT), chest radiography, and thin-section CT. Four of 25 patients (16% ), who had obvious signs on plain films suggestive of pre-existing disorder s unrelated to AS were excluded, RESULTS: Fifteen of 21 patients (71%) had abnormalities on thin-section CT. The most frequent abnormalities were thickening of the interlobular septa in seven of 21 patients (33%), mild bronchial wall thickening in (6/21, 29% ), pleural thickening and pleuropulmonary irregularities (both 29%) and lin ear septal thickening (6/21, 29%). In sis patients there were no signs of p leuropulmonary involvement. Eight of 15 patients (53%) with abnormal and fo ur of six patients (67%) with normal CT findings revealed mild restrictive lung function impairment. CONCLUSION: Patients with AS but a normal chest radiograph frequently have abnormalities on thin-section CT, As these abnormalities are usually subtle and their extent does not correlate with functional and clinical data, the overall routine impact of thin-section CT in the diagnosis of AS is limite d. (C) 2000 The Royal College of Radiologists.