The prognostic value of loculations in parapneumonic pleural effusions.

Forty-eight patients with pleural effusions who had sonographically directed thoracocentesis were evaluated retrospectively for radiologic findings, pleural fluid chemistries, and outcome. Loculation was found to be a radiologic marker of diagnostic and prognostic significance. The presence of loculations correlated with exudative pleural fluid chemistries, but no radiologic finding was specific for empyema. "Extreme" pleural fluid chemistries were associated with loculation, but not with empyema. Patients with loculated effusions had larger effusions, longer hospitalizations, and more frequent tube thoracostomy procedures than patients with nonloculated effusions. Light's criteria for tube thoracostomy were found to be unreliable in patients with loculated parapneumonic effusions or in patients treated with prolonged antibiotic therapy prior to thoracocentesis.