An Asymmetric Chest X-ray

There is near complete right sided white out on this CXR. There is no evidence of surgical clips on the right to indicate that the cause of the white out is pneumonectomy, also there is some air noted in the mid lung and upper lung fields. This patient has a large pleural effusion. There are between 1 and 2 million pleural effusions diagnosed each year, with the majority being secondary to heart failure, pneumonia, and underlying malignancies. Pleural effusions and pneumothoraces are the most common of the pleural disorders.

As always a good history and physical examination is key. Typical symptoms include pleuritic chest pain, cough, shortness of breath, orthopnea, fever, arthralgia, and malaise. Patients should be asked about TB risk factors, occupational exposures, asbestos exposures, any risk factors and symptoms of underlying malignancy, etc. The exam should focus on the breathing mechanics of the patient. Listen for abnormal lung sounds such as diminished breath sounds, decreased tactile fremitus, and dullness to percussion. Look for evidence of underlying malignancy (you may be surprised by what patients are not willing to disclose); evaluate the digits for evidence of clubbing.

Imaging:

The PA/Lat CXR is usually the first go to modality with pleural fluid showing up on lateral view starting at approximately 50 mL of fluid and on PA view once at approximately 200 mL.

Lung Ultrasound is great because it is more sensitive than physical examination in determining the true extent of the effusion, and in determining if any loculations are present. Most importantly, if the fluid is going to be drained the use of US can make for a more accurate and safer procedure.

Thoracentesis:

Thoracentesis should be performed for new pleural effusions that are not explained by causes such as the edematous states e.g. heart failure, chronic renal failure/ESRD, chronic liver failure, or by small parapneumonic effusions. Below is a figure of how thoracentesis can be performed.

The two broad categories of pleural effusions are transudates or exudates, with an effusion being considered exudative as determined by Light’s Criteria if the following are present:

1. Pleural fluid total protein/serum total protein>0.5.
2. Pleural fluid LDH/serum LDH>0.6.
3. Pleural fluid LDH >2/3 upper limit of the normal serum value.

There is a common scenario where the LIght’s criteria will misclassify a transudative effusion as an exudative one: during ongoing diuresis of transudative effusions. In this setting calculate a pleural fluid to serum albumin gradient which if >1.2 g/dl will be considered a transudate.

Wilcox ME, Chong C, et al. Dow this patient have an exudative pleural effusion? The rational clinical examination systematic review. JAMA. 2014;311(23):2422-2431.