Bilateral Pleural Effusions: Do Both Sides Need to be Tapped?

Abstract & Commentary

Synopsis: In this retrospective review of 33 patients with bilateral pleural effusions who had the fluid on both sides tapped, the cause of the effusions was most often cardiac disease and seemed to be the same on both sides in every case.

Source: Kalomenidis I, et al. Chest. 2003;124:167-176.

Kalomenidis and colleagues at st. thomas Hospital in Nashville reviewed their prospectively accumulated database of all pleural fluid specimens obtained from both inpatients and outpatients under ultrasound guidance since 1997 in their institution. There were 33 patients (2.5%) who had bilateral effusions and had both sides tapped on the same day. After incomplete data and inconclusive clinical diagnoses, were excluded, 27 patients comprised the study population. There was no significant difference in the mean values of any pleural fluid characteristic between right and left sides, and no case in which one side was an exudate and the other side a transudate. In their primarily cardiac hospital, the most common etiologies were post-coronary artery bypass grafting (CABG; 13 patients; 48%) and congestive heart failure (12 patients; 44%). The only other diagnoses were renal failure and malignant pericardial effusion-associated pleural effusions in a patient with lung cancer. Kalomenidis et al concluded that, in patients with bilateral pleural effusions, diagnostic thoracentesis need not be performed on both sides unless there is a specific indication.

Comment by David J. Pierson, MD

Can we take the results of this study to mean that ICU patients with bilateral effusions only need to have one side tapped? I don’t think so, for several reasons. Although this is the only study published so far to focus specifically on bilateral pleural effusions, it dealt with both outpatients and inpatients in an institution that sees mainly patients with cardiac disease. The situation may be different in the general medical-surgical ICU population.

Pleural effusions in ICU patients have been the subject of previous study. Mattison and associates studied 100 consecutive medical ICU patients using both chest x-rays and ultrasound and found pleural fluid in 62 of them.1 The fluid was bilateral in 34 (55%). Congestive heart failure was the most common etiology. This study was done by a group with a special issue in pleural disease, and special efforts were made to detect effusions, many of which were small.

The differential diagnosis of bilateral pleural effusions is somewhat different from that for fluid collections in only 1 hemithorax. Bilateral effusions are most likely to be due to congestive heart failure, post-CABG (the mechanism for which is unknown), or metastatic malignancy. Less commonly, they can occur in drug-induced pleuritis, rheumatoid disease, systemic lupus erythematosus, and benign asbestos-related pleural inflammation. They can also be seen in pulmonary embolism, pericardial disease, and renal failure. However, the most worrisome possible etiology in a critically ill patient is infection. Although bilateral pleural effusion can occur in tuberculous pleuritis, this is unusual. Parapneumonic effusions are common, however, and of greatest concern is the possibility of bilateral parapneumonic effusions, one of them an empyema. In such an occurrence, if only the noninfected side was sampled by thoracentesis, substantial morbidity or even mortality could result from not initially tapping the other side. This is because a number of outcome measures in patients with parapneumonic pleural empyema are strongly correlated with rapidity with which complete pleural drainage or other definitive surgical procedure is carried out.

Kalomenidis et al recommend bilateral thoracentesis under the following circumstances: coexisting unilateral parenchymal abnormality; pleural effusions of markedly different sizes; parapneumonic effusions; metastatic malignant effusions; or if fluid on non-tapped side persists after successful therapy for the side that was tapped. I concur with these recommendations, and would add 2 more for patients in the ICU:

  • When one pleural space has recently been invaded, or might have been invaded, as with penetrating trauma, surgery, attempted line placement, or endoscopy, and the effusion appears or increases within a day or two of that event; and
  • When a patient with bilateral effusions from heart failure or other benign condition develops a new episode of clinical sepsis.


1. Mattison LE, et al. Chest. 1997;111:1018-1023.