Prognostic features of residual pleural thickening in parapneumonic pleural effusions.

The objective of the study was the identification of predictive factors for the development of residual pleural thickening (RPT) in patients with parapneumonic effusion. The design of the prospective study involved investigating patients with parapneumonic pleural effusions diagnosed between March 1991 and December 2000 in the respiratory department of Hospital Ramón y Cajal (Madrid, Spain) which is a 1,500 tertiary-care hospital. The clinical and radiological characteristics and measurements of microbiological and biochemical variables in the pleural fluid taken from the patients were studied. RPT was defined in a posteroanterior chest radiograph as pleural thickening of > or = 10 mm measured at the lateral chest wall at the level of an imaginary line, tangent to the diaphragmatic dome. A total of 48 of the 348 patients studied (13.79%) were found to have RPT. Among the factors studied, only presence of pus in the pleural space, Fine classes IV and V, temperature > or = 38 degrees C and delayed resolution of pleural effusions after diagnosis (> 15 days) were independently associated with the risk of RPT. This study showed that significant residual pleural thickening was not a common complication of parapneumonic pleural effusions. There are certain risk factors for the development of residual pleural thickening. However, this complication was not associated with long-term functional repercussions in the series of patients involved in this study.