Tuberculous Pleuritis: Key CT Imaging Features and Diagnostic Insights

Tuberculous pleuritis, a distinct form of extrapulmonary tuberculosis, arises as a complication of pulmonary TB infection and is characterized by inflammation of the pleural membranes. It remains one of the leading causes of pleural effusion in regions where tuberculosis is endemic. Computed tomography (CT) plays a crucial role in diagnosing and assessing the extent of this condition, offering detailed visualization of pleural and parenchymal changes that may not be evident on conventional chest X-rays.

Understanding CT Findings in Tuberculous Pleuritis

The radiological appearance of tuberculous pleuritis on CT scans varies significantly depending on the volume of pleural fluid present. In the early stages, when fluid accumulation is minimal—typically less than 300 mL—the CT scan may appear nearly normal or show only subtle findings. At this stage, definitive signs of effusion might be absent, making diagnosis challenging without clinical correlation.

Small-Volume Pleural Effusions

When fluid levels are low, the most notable observation is often a blunted costophrenic angle, although this becomes more apparent as the volume increases beyond 500 mL. Interestingly, patient positioning during imaging can influence findings: in supine CT scans, fluid tends to layer along the posterior and lateral chest walls, spreading out rather than pooling sharply in the costophrenic recesses. This redistribution can create the illusion of a preserved, sharp costophrenic angle, potentially leading to underestimation of effusion volume if not interpreted carefully.

Moderate to Large Pleural Effusions

As fluid accumulates to moderate levels, CT imaging typically reveals a homogeneous increase in density within the lower thorax. The classic crescent-shaped or meniscus-like opacity is commonly observed, with the fluid layering along the lateral chest wall and rising higher peripherally than medially—a hallmark sign of free-flowing pleural effusion.

In cases of massive effusion, the affected hemithorax appears largely opacified due to widespread, uniform high-density shadows displacing lung tissue. This extensive consolidation often pushes the mediastinum toward the contralateral (unaffected) side—a phenomenon known as mediastinal shift. Such displacement serves as an important clue in differentiating large effusions from other conditions like atelectasis, where the mediastinum would shift toward the collapsed lung.

Additional Imaging Clues Suggestive of Tuberculosis

Beyond fluid volume assessment, CT scans may reveal ancillary features highly suggestive of a tuberculous etiology. These include thickened pleural membranes, loculated effusions (where fluid is compartmentalized due to adhesions), and associated parenchymal abnormalities such as subpleural nodules, tree-in-bud opacities, or evidence of prior granulomatous disease. Pleural enhancement after contrast administration further supports active inflammation, commonly seen in infectious processes like TB.

Importantly, while CT cannot definitively confirm tuberculosis on its own, it provides critical context for guiding further diagnostic steps—such as thoracentesis, pleural biopsy, or molecular testing (e.g., GeneXpert MTB/RIF)—which are essential for microbiological confirmation.

Clinical Implications and Role in Patient Management

Accurate interpretation of CT findings enables clinicians to assess disease severity, monitor response to anti-tuberculosis therapy, and detect complications such as empyema or fibrothorax. Early detection through imaging, combined with clinical evaluation and laboratory testing, improves patient outcomes by facilitating timely intervention.

In summary, CT imaging is an indispensable tool in the evaluation of suspected tuberculous pleuritis. Recognizing the spectrum of imaging patterns—from minimal effusions to massive opacification with mediastinal deviation—empowers healthcare providers to make informed decisions and deliver effective, targeted care.