Diagnosis: Reactivation of pulmonary TB

Formation of single or multiple, thin- or thickwalled cavities on either side of the lung fields, especially in the apical or posterior segment and superior segment of the lower lobe, is considered an important hallmark of reactivation pulmonary tuberculosis. 1 Differential diagnosis of a cavitory lesion on chest x-ray includes infectious diseases like common bacterial infections (Staphylococcus, Klebsiella, anaerobes), necrotizing pneumonias and lung abscesses, septic pulmonary emboli, fungal infections, parasitic infections, and, most importantly, mycobacterial infections in a country like India where tuberculosis is rampant. However, noninfectious causes include malignancies (squamous cell carcinoma of the lung), rheumatologic diseases, pulmonary infarcts, and Wegener granulomatosis. 2 How does “tennis racket” form? Involvement of bronchus in the tuberculous process, causing its narrowing or occlusion with the dilatation of its distal part beyond this narrowing, due to the local wall destruction with weakening, appears as a ring shadow (tuberculous cavity) while the proximal part of the draining bronchus (toward hilum) is also either nar rowed, thickened, or dilated by the tuberculous process, giving it the appearance of a “tennis racket” shadow. 3 Histological features of the wall of such a “cavity” are similar to those of the bronchial wall with or without tuberculosis foci in it. 4