Pleural Pustule-a Novel Thoracoscopic Appearance of Pleural Tuberculosis

Background: Thoracoscopic pleural biopsy is the gold standard for diagnosing tubercular pleural effusion (TPE). Various thoracoscopic appearances like sago grain nodules, caseous necrosis, and adhesions have been described in TPE. However, none of these have high specificity for diagnosing TPE. In this study we evaluate a novel finding on thoracoscopy, the " Pleural Pustule."

Methods: This is a retrospective analysis of patients who underwent thoracoscopy for undiagnosed pleural effusion. Visual inspection of the pleura was performed to identify abnormalities. Biopsies were obtained from those areas and sent for histopathology, acid fast bacillus (AFB) smear, culture, and Xpert MTB/Rif assay. Pleural pustule was defined as a pus filled nodule on the pleural surface.

Results: Of the 259 patients included, 92 were diagnosed with TPE. Pleural pustule(s) were identified in 16 patients with TPE. Presence of pleural pustule had a sensitivity, specificity, positive predictive value, and negative predictive value of 17.4%, 100%, 100% and 68.7%, respectively, for diagnosing TPE. Histopathology of pleural pustule demonstrated necrotizing granulomas in all. In patients with pleural pustule, a microbiological diagnosis of tuberculosis was achieved in 93.7% patients (AFB smear, Xpert MTB/Rif assay, and MTB culture positive in 31.3%, 93.7%, and 43.7% cases, respectively). There is a strong association between pleural pustule and positive Xpert MTB/Rif assay ( P =0.002) and microbiologic confirmation of diagnosis ( P =0.017).

Conclusion: The presence of pleural pustule on thoracoscopy has a high positive predictive value for TPE. In tuberculosis-endemic countries, this can be considered suggestive for TPE. When identified, a biopsy from the pleural pustule should be performed as it will likely yield a positive microbiologic diagnosis.