Pleural effusion: Clinical sciences

Pleural effusion refers to a fluid that accumulates between the parietal pleura and visceral pleura, known as the pleural space, and can be caused by conditions such as congestive heart failure, pneumonia, cancer, cirrhosis, and kidney disease, to name a few.

Depending on the fluid characteristics and how it accumulates, pleural effusions are broadly classified as either transudates or exudates. Transudate occurs when too much fluid starts to leave the capillaries, either because of increased hydrostatic pressure or decreased oncotic pressure. On the other hand, exudate is typically associated with inflammation, which allows immune cells and large proteins to leak out of the capillaries.

Based on the type of fluid and etiology, exudates can be further subdivided into parapneumonic effusions, malignant effusions, inflammatory effusions, and chylous effusions.

Now, if you suspect a pleural effusion, first perform an ABCDE assessment to determine if your patient is unstable or stable. If unstable, stabilize their airway, breathing, and circulation. Next, obtain IV access and provide supplemental oxygen, if needed. Finally, put your patient on continuous vital sign monitoring, including heart rate, blood pressure, and pulse oximetry.

Alright, now let’s go back to the ABCDE assessment and take a look at stable individuals. If the patient is stable, you should start with acute management, like obtaining IV access, providing supplemental oxygen, and initiating continuous vital sign monitoring. Next, you should perform a focused history and physical, and order labs, including a CBC.

Individuals with pleural effusion typically report cough, shortness of breath, and pleuritic chest pain, which is typically described as a severe, sharp pain that worsens with breathing. Some patients may also report a fever.

On the flip side, physical exam findings usually include dullness to chest percussion, as well as decreased tactile fremitus and absent basilar breath sounds on the affected side.

On labs, CBC might show leukocytosis. At this point, you should suspect pleural effusion, so order an imaging study.

Including a chest X-ray, point of care ultrasound or POCUS, or a CT to confirm the diagnosis.

If the chest X-ray reveals blunting of the cardiophrenic and costophrenic angles, it indicates a pleural effusion. You may also see a meniscus sign, which is when accumulated fluid completely surrounds the base of the lung. A chest X-ray might not show a pleural effusion until at least 250 ml of fluid has accumulated.

Often, a lateral decubitus X-ray can more accurately demonstrate a smaller effusion, and might also help you determine if the fluid is loculated.

Alternatively, you can use POCUS, which can detect as little as 5 mL of fluid! POCUS will typically reveal a fluid-filled, or anechoic, collection just above the diaphragm. You may also see a spine sign, which refers to the visualization of the part of the thoracic spine due to the presence of fluid that is typically obscured by air in the lungs.

Lastly, you can order a CT to further characterize the effusion, help find the underlying cause, and aid in potential treatment such as thoracentesis or chest drains. Your imaging studies should confirm the presence of pleural effusion. If the imaging findings are inconsistent with pleural effusion, you should consider an alternative diagnosis.

Now, once you confirm the presence of a pleural effusion, your next step is to determine the cause. First, assess whether or not your patient has congestive heart failure, or CHF for short. Physical exam findings, such as tachypnea, jugular venous distension, peripheral edema, rales, or an S3 heart sound are highly suggestive of CHF. In this case, start CHF management, typically with diuretics.

Next, assess the patient’s response to treatment. If there’s an adequate response to the diuretics, meaning the amount of pleural fluid is reduced, continue current management! However, if your patient has an inadequate response, with no reduction of pleural fluid, proceed with a therapeutic thoracentesis.

Here’s a clinical pearl! Large effusions may reaccumulate despite therapeutic thoracentesis. If this is the case, your patient may need to be evaluated by the surgery team for a chest tube or video-assisted thoracoscopic surgery, or VATs for short.

Ok, now let’s take a look at individuals that present with findings inconsistent with congestive heart failure! In this case, proceed with diagnostic and therapeutic thoracentesis! This includes removing accumulated fluid from the pleural cavity, and sending it for lab analysis.

Be sure to order a cell count with differential, total protein, LDH, glucose, and cholesterol and triglycerides. At the same time, order serum total protein and LDH.

Okay, so once the lab results are back, analyze the pleural fluid by using the “Light’s Criteria fluid analysis”. This will determine whether the pleural fluid is a transudate or an exudate.

There are three criteria, which are the ratio of pleural protein, or “pProtein” to serum protein or “sProtein”, the ratio of pleural LDH or “pLDH” to serum LDH or “sLDH”, and pleural fluid LDH levels.

So, in transudates, the ratio of pleural protein to serum protein is less than 0.5; pleural LDH to serum LDH is less than 0.6; or pleural fluid LDH is less than 2/3 of the high-normal level for serum LDH. If any of these conditions are present you can diagnose disease specific effusion. Transudative fluid is often a result of conditions that can lower oncotic pressure, and increase hydrostatic pressure in the pleural space, such as CHF, cirrhosis, or nephrotic syndrome. If the patient has a transudate, it’s important to treat the underlying cause.