Study objectives: To determine whether, in patients with bilateral pleural effusions, the main cellular and biochemical features of the pleural fluid on the right side differ from or correlate with those on the left side. We examined lactate dehydrogenase (LDH), glucose, and total protein (TP) levels, RBC count, nucleated cell count (NCC), and differential cell count.
Patients and methods: Twenty-seven patients with bilateral pleural effusions, including 13 patients with effusions after coronary artery bypass graft surgery, 12 patients with congestive heart failure, 1 patient with malignant pericarditis, and 1 patient with renal failure, were studied retrospectively.
Results: The right-sided and the left-sided pleural effusions did not differ in the mean TP (p = 0.38), glucose (p = 0.31), and LDH (p = 0.39) levels, RBC count (p = 0.31), NCC (p = 0.96), and the percentage of neutrophils (p = 0.22), lymphocytes (p = 0.73), mononuclear cells (MNCs) [p = 0.49], and eosinophils (p = 0.65). The bias ± precision was 0.1 ± 0.64 g/dL for TP, − 2.7 ± 23 mg/dL for glucose, 41 ± 362 IU/L for LDH, 6,100 ± 62,900 cells/μL for RBC count, − 36 ± 1,043 cells/μL for NCC, − 2.9 ± 11.6% for the percentage of neutrophils, 1.15 ± 17% for the percentage of lymphocytes, 2.3 ± 17% for the percentage of the MNCs, and − 0.15 ± 5.4% for the percentage of eosinophils. Moreover, there was a close correlation between the right-sided and the left-sided pleural effusions concerning TP level (r = 0.85, p < 0.001), glucose level (r = 0.78, p < 0.001), LDH level (r = 0.71, p < 0.001), RBC count (r = 0.66, p < 0.001), NCC (r = 0.60, p = 0.001), and the percentage of neutrophils (r = 0.77, p < 0.001), lymphocytes (r = 0.77, p < 0.001), MNCs (r = 0.74, p < 0.001), and eosinophils (r = 0.84, p < 0.001).
Conclusion: Since the pleural fluid findings tend to be similar in both sides of patients with bilateral pleural effusion, we suggest that diagnostic thoracentesis may not need to be performed on both sides, unless there is a specific clinical indication.