Does an asymptomatic patient with a small left pleural effusion require intervention?

From the Guidelines

No, an incidental tiny left pleural effusion in an asymptomatic patient typically does not require intervention. According to the British Thoracic Society guidelines for the management of pleural infection 1, pleural effusions with maximal thickness <10 mm on ultrasound scanning can be observed, with pleural fluid sampling if the effusion enlarges. This approach prioritizes minimizing unnecessary interventions and their associated risks, such as pneumothorax, bleeding, or infection, while still allowing for monitoring of the effusion's size and the patient's symptoms. Key points to consider in the management of such patients include:

• The use of ultrasound scanning to assess the size of the pleural effusion and guide any potential interventions 1
• The recommendation to observe small effusions rather than immediately proceeding with invasive sampling or drainage 1
• The importance of patient education regarding symptoms that would warrant earlier evaluation, such as new shortness of breath, chest pain, or fever
• The potential for tiny pleural effusions to represent normal physiologic fluid or minor inflammatory processes that can resolve without intervention. Given the low risk associated with small, asymptomatic pleural effusions and the potential complications of intervention, a conservative approach with observation and follow-up imaging is generally preferred, as supported by the guidelines 1.

From the Research

Incidental Tiny Left Pleural Effusion in Asymptomatic Patients

• The presence of a small pleural effusion in an asymptomatic patient may not necessarily require immediate intervention 2.
• According to a study published in 2007, small amounts of pleural fluid can be difficult to identify with imaging methods, but may still be an important finding in certain cases 2.
• The study suggests that the term "pleural fluid" should be used to describe a physiologic pleural space condition, while "pleural effusion" should only be used in cases of pleural involvement or illness 2.

Diagnostic Approach

• In patients with heart failure, pleural effusions can be either transudates or exudates, and the characteristics of the fluid can help determine the underlying cause 3.
• A study published in 2001 found that exudates with a specific cause were more likely to have at least two of Light's criteria, while exudates without a known cause were more likely to have been treated with intravenous diuretics 3.
• Lung ultrasound has become a leading real-time method for demonstrating small pleural effusions, and can help guide therapeutic thoracentesis 4.

Treatment Options

• Therapeutic thoracentesis can be an effective treatment for pleural effusions in patients with heart failure, and can provide immediate and long-lasting symptomatic relief 4.
• A study published in 2020 found that lung ultrasound-guided therapeutic thoracentesis was feasible, safe, and efficient in patients with heart failure and pleural effusion 4.
• The treatment of pleural effusion depends on the underlying cause, and can range from pleurodesis to thoracoscopy and video-assisted thoracoscopy, to the placement of a permanently indwelling pleural catheter 5.

Ongoing Research

• A randomized controlled trial is currently underway to investigate the effectiveness of thoracentesis in alleviating pleural effusion in patients with acute heart failure 6.
• The trial will compare the outcomes of patients who receive up-front thoracentesis in addition to pharmacological therapy with those who receive pharmacological therapy alone 6.