Miliary Tuberculosis of the Lung : Thin-section CT findings and Clinical correlation

Abstract

Abstract Purpose To analyze high resolution CT (HRCT) findings of miliary tuberculosis and to identify CT features predictive of poor prognosis.

Materials and Methods We retrospectively reviewed chest HRCT scans of 41 patients (12 men, 29 women; mean age 52.8 years) with microbiologically (n=30) or clinically (n=11) proven miliary tuberculosis. The size and profusion of upper lung nodules were compared with those of lower lung ones by independent t-test, and the relationship between individual HRCT features and the time required for miliary nodules to radiographically disappear with anti-tuberculous medication were analyzed using Pearson’s correlation. CT features were compared between four expired and 25 improved patients.

Results HRCT scans showed miliary nodules in 39 patients (95%), which varied in size from 0.7 to 5 mm, with either sharply (n=32, 82%) or poorly (n=7, 18%) defined margins. The nodules were mostly uniform (n=33, 85%), but sometimes upper- (n=2, 5%), middle- (n=2, 5%), or lower-lung (n=2, 5%) predominant in cephalocaudal distribution and random (n=34, 87%) in intralobular distribution. In 25 patients (61%), areas of ground glass opacities (GGOs) were observed with variable extent and distribution. HRCT also revealed interlobular septal thickening (n=22, 54%), localized preexisting tuberculous lesions (n=16, 39%), pleural effusion (n=16, 39%), lymphadenopathy (n=14, 34%), and findings of bronchogenic spread (n=6, 15%). Upper lung nodules (1.37 ± 0.62 mm) were significantly larger in size than lower-lung ones (1.10 ± 0.25 mm) (p=0.0147) on HRCT. But lower lung zone (19.1 ± 8.1 N/cm2) had more profusion than the upper lung zone (17.3 ± 8.4 N/cm2). In 24 patients who were followed up until or beyond radiographical clearing of miliary nodules, the size and profusion of nodules on HRCT were not significantly correlated with the time to the radiographical clearing. When thin-section CT features were compared between 25 survived and four expired patients, only the extent of GGOs (p=0.046) and pleural effusion (p=0.009) showed significant correlation.

Conclusion Miliary nodules and GGOs are the main HRCT findings of miliary tuberculosis. Contrary to popular belief, in patients with miliary tuberculosis, upper-lung nodules are significantly larger than lower-lung ones. But the size and number of nodules did not correlate with the time required for miliary nodules to disappear. Higher extent of GGOs and pleural effusion may be poor prognostic indicators of miliary tuberculosis.