Pleural Thickening and Pleural Calcification

Organizing Effusion

Organization of an infected pleural effusion (empyema) is one of the most common causes of pleural thickening. The detection of a small amount of associated pleural fluid may seem unimportant but is vital for diagnostic thoracentesis. ⁴⁷⁸ The fluid may appear to be nondiagnostic, but it provides material for culture and cytologic studies. An organizing fibrothorax is definitely less diagnostic because it usually consists of chronic inflammatory cells and fibrosis. It may be the end result of a variety of bacterial, fungal, and tuberculous pulmonary infections. In such cases, the radiologic finding of pleural thickening is nonspecific, and the radiologic diagnosis usually depends on associated pulmonary findings. Apical pulmonary cavities with associated pleural thickening are characteristic of prior granulomatous infection, such as tuberculosis or histoplasmosis. ³⁸⁸ A strongly reactive skin test may confirm the diagnosis. Additional complications should be suspected in patients with old cystic lesions or cavities who develop a new pleural opacity in the area of the old abnormalities. A new area of pleural thickening in the same vicinity is suggestive of new complications, which include reactivation of tuberculosis, scar cancer, or a new infection, such as aspergilloma, which develops in old cavities and may cause pleural thickening. ³⁴⁰ As with other causes of inflammatory pleural thickening, the histologic appearance of the pleural disease secondary to aspergilloma is nonspecific. The fungus is not usually identifiable in the pleural reaction.

The less specific appearance of extensive pleural thickening over the bases, with associated parenchymal scars, can best be diagnosed as chronic empyema when a definite history of previous pneumonia is obtained. Some noninfectious causes of pleural effusion, such as rheumatoid disease, occasionally fail to resolve, with the final result of a thick pleural reaction ( Fig 5.3 ). ³⁶⁹ A history of known rheumatoid arthritis may suggest this diagnosis. In addition, positive results of serologic studies for rheumatoid factor may also suggest the diagnosis, particularly if there is a history of thoracic disease prior to the onset of joint disease.