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Patients with pleural effusions frequently present a diagnostic and therapeutic challenge. The diagnosis is based on the interpretation of the results of thoracentesis or pleural biopsy. When a malignant tumor metastasizes to the pleura, tumor cells can be seeded over the mesothelial surface or in the subserous layer. In the former situation, tumor cells are abundant in pleural fluid, but in the latter, few malignant cells are exfoliated into the pleural cavity, and microscopic deposits may not be visualized at thoracoscopy. Pleural lavage cytologic study at the time of thoracoscopy has not been studied. The purpose of this study was to assess the value of thoracoscopic pleural lavage as an adjuvant in the diagnostic workup of patients with exudative pleural effusions. Fifty patients with exudative pleural effusions were investigated by pleural fluid cytologic findings, Abram's pleural biopsy, thoracoscopy, and pleural lavage cytologic findings. After aspiration of all pleural fluid, 300 mL saline was instilled into the pleural cavity and then recovered for cytologic analysis. The final diagnoses were 32 malignant (64%), 15 tuberculous (30%), and 3 idiopathic (6%) effusions. In the malignant group, thoracoscopic biopsy had the highest yield (94%) followed by lavage cytologic analysis (84%), fluid cytologic analysis (62%), and biopsy with Abram's needle (50%). The sensitivity of combined thoracoscopy and lavage cytologic analysis was 96%. In the patients with tuberculous pleuritis, the yield from the pathologic examination of the biopsy specimen was 93% with thoracoscopy and 60% with the Abrams needle. The diagnostic yield with cytologic analysis on pleural lavage fluid is significantly higher than that on pleural fluid. This is probably because the cells in the lavage fluid are fresher and better preserved than those in the regular pleural fluid, which may have undergone degenerative changes, yielding false-negative results. Pleural lavage cytologic analysis should be performed in patients with suspected malignant pleural effusion who are subjected to diagnostic thoracoscopy, because it may provide additional information to thoracoscopic biopsy.

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