Pleural Effusions

I. Problem/Condition.

A pleural effusion is an abnormal accumulation of pleural fluid within the pleural space. The most common cause of pleural effusion is congestive heart failure, which tends to have a better prognosis, compared to less common causes of pleural effusions associated with cirrhosis or malignancy.

The pleural space lies between the chest wall and lung, and usually contains a small amount of fluid, which helps the two spaces be connected to each other. A pleural effusion forms when there is an imbalance between the production and absorption of the fluid in the pleural space. Fluid gets into the pleural space either by osmosis from normal venous and pulmonary circulation, or by direct leakage from damaged vessels in the venous and pulmonary circulation system. While the lung lymphatic system is responsible for absorbing this fluid, it can only absorb a small volume of fluid. Fluid tends to accumulate first in the interstitium and then in the pleural space.

II. Diagnostic Approach.

A. What is the differential diagnosis for this problem?

Differential Diagnosis for Transudative Effusion includes:

CHF (90%)

Cirrhosis (hepatic hydrothorax)

Pulmonary embolism

Nephrotic syndrome

Peritoneal dialysis


Constrictive pericarditis

SVC syndrome

Differential diagnosis for Exudative Effusion includes (the list is extensive and only a few are listed here):



Connective tissue disease




Drug reaction


Esophageal rupture


1. Historical information important in the diagnosis of this problem.


As with other diseases, after stabilizing the patient, the next most important step is taking a detailed clinical history. The period of time over which the pleural fluid has accumulated is particularly important, e.g., the presence of marked dyspnea should alert the provider that either the effusion is quite large, or there was a rapid accumulation. Rarely, pleural effusions may also cause cardiac tamponade even in the absence of a pericardial effusion, which could lead to significant hemodynamic consequences.


Physical exam:

The four major components of the lung exam are inspection, palpation, percussionand auscultation. Observation of the patient’s breathing pattern, in particular, can provide valuable information.


General appearance, breathing pattern: labored breathing, accessory muscle use, diaphoresis, gasping for air, inability to speak in full sentences, etc.

Presence or absence of cyanosis, particularly perioral, enlarged jugular veins.

Any audible sounds associated with breathing, wheezes, stridor, that one can hear without the stethoscope.

Paradoxical abdominal wall movement. Normally, during inspiration, because of the diaphragm descent, the intra-abdominal content is pushed down and the wall outward. When there is severe diaphragmatic flattening the abdominal wall moves inward during respiration.

Check for any chest wall or spine deformities.


Accentuating normal chest excursion: processes that lead to abnormal chest excursions, such as pleural effusion, or pneumothorax (fluid or air) can lead to an abnormal movement of the thumb of the hand placed on the patient chest wall posteriorly. It is important to note excursion may only be seen in the presence of a large effusion.

Tactile fremitus: normal lung transmits palpable vibration through the chest wall. In pleural effusion, the lung is compressed and thus, fremitus is decreased.


This exam maneuver can particularly help with the diagnosis of pleural effusion.

The technique involves striking over the chest wall surface; the result is a resonant sound when the stricken surface covers an air-filled structure, such as the normal lung, as opposed to fluid which leads to a dull sound.


In pleural effusion, breath sounds are reduced or inaudible.

Presence of egophony changes at the top of the pleural effusion.

Rarely, one can identify pleural friction rub.


Imaging studies

The next step in the process of identifying a pleural effusion is an imaging study, such as an ultrasound, chest X-ray, or computed tomography (CT). These studies, also help with the size, symmetry of the effusion, as well as the surrounding lung anatomy. A simple upright AP or PA chest X-ray will detect the presence of volumes of fluid larger than 300 cc. When a pleural effusion is suspected but not seen on the upright imaging studies, a decubitus film should be obtained.

When a patient is diagnosed with pleural effusion, every effort should be made to identify the cause. Pleural effusions may accompany many other diseases, such as cirrhosis, heart failure, venous thromboembolism/ pulmonary embolism, or complicated pneumonia.

For example, if a patient has bilateral and symmetrical pleural effusions, the most common cause is CHF, assuming that other clinical signs suggestive of CHF are present and there is absence of fever. Eighty percent of patients with CHF-related pleural effusions have bilateral effusions, and 75% of these effusions resolve after diuresis. In the case of presumed CHF, it is appropriate to empirically diurese and assess the effusion response. Note that renal failure and cirrhosis (i.e., volume overload) can also lead to bilateral and symmetric pleural effusions. After several days of appropriate diuresis or if new symptoms develop, a thoracentesis is warranted to identify the cause of the effusion.

In summary, any pleural effusion should be tapped, unless:

There is not enough fluid to tap.

The patient has clinical signs of CHF, does not have a fever, and has bilateral pleural effusions that resolve within 3 days.


A diagnostic thoracentesis is the procedure by which the fluid in the pleural space is removed to aid in diagnosis.

Light’s criteria helps with the analysis of pleural effusions and can suggest an exudate or transudate.

Checking serum and fluid LDH and total protein by using Light’s criteria (satisfying any ONE criteria means it is exudate) helps identify the exudative effusion:

  • Pleural Total Protein/ Serum Total Protein > 0.5

  • Pleural LDH/ Serum LDH > 0.6

  • Pleural LDH > 2/3s of the upper limit of normal for serum LDH

Diagnostic recommendations for exudative effusions

The following diagnostic recommendations pertain to exudative effusions:

If the fluid is exudative, further pleural diagnostic tests should be considered, such as white blood count (WBC) with differential, glucose level, amylase, cytology, gram stain, and cultures, pleural fluid pH.

Pleural fluid pH is useful in the assessment of parapneumonic effusions (exudative effusion that can complicate pneumonia). A pH below 7.20 (measured with a blood-gas machine) suggests the need for drainage of the pleural space. Other causes of a low pH include lupus (<20%), tuberculosis (<20%), malignancy, and esophageal rupture.

If the work up is consistent with a parapneumonic effusion, then both a diagnostic and therapeutic thoracentesis are indicated. Consider a therapeutic tap, see criteria below.

If these methods do not yield a diagnosis, and if the differential is predominantly lymphocytic, consider sending markers for tuberculosis, such as adenosine deaminase or DNA PCR for tuberculosis.

If none of the above yield a diagnosis, then rule out a pulmonary embolus (PE) by CT chest with contrast. Pleural effusions may occur in 10% of PEs. Of such effusions, 25% are transudative, and 75% are exudative.

If the etiology of the exudate is still unknown after the above workup, then a pleural biopsy is generally indicated. This procedure can be done through various methods, such as image-guided needle biopsy or thoracoscopic biopsy. Biopsy can particularly help in diagnosing tuberculosis or a malignancy.

C. Criteria for Diagnosing Each Diagnosis in the Method Above.

The appearance of the pleural fluid may guide management while other tests are pending. Alarming signs include pus as a sign of an empyema, fluid that is the same color as a feed going in through a tube, or milky fluid as in a chylothorax. Pale yellow fluid may be associated with exudates; bloody fluid with malignancy, trauma, and pulmonary infarction; black with an Aspergillus infection; and dark green with bilothorax.

The WBC and differential are also used to help determine the cause of a pleural effusion. In pleural fluid that is neutrophil predominant (greater than 50%), 81% of these effusions are parapneumonic, with PE and pancreatitis as less common causes. In pleural effusions that are lymphocyte-predominant, 96% of these are cancer or tuberculosis. If the WBC in the pleural fluid is greater than 10% eosinophils, then 2/3 of the time this indicates blood or air in the pleural space. If the fluid is monocyte-predominant, this indicates a chronic non-specific process.

A positive gram stain and culture can aid antibiotic selection and need for therapeutic tap.

Pleural fluid pH can be important in determining prognosis, acuity, and the need for therapeutic tap. ANY patient with a pleural fluid pH of less than 7.2 should have a therapeutic tap. A pleural fluid pH of <7.2 is associated with a life expectancy of less than 30 days.

A patient with a pleural fluid pH of less than or equal to 7.3 and any of the following:

Effusion taking up greater than 40% hemithorax on imaging

Positive pleural fluid Gram stain or culture

Multiple loculations

Toxic/unstable Patient

Staph aureus, Klebsiella or Pseudomonas aeruginosa pneumonia

A glucose of <60 is associated with a parapneumonic or malignant effusion.

An N-terminal BNP of greater than 1500 pg/mL has a 91% sensitivity and 93% specificity for a CHF associated effusion.

An adenosine deaminase level may be sent on the pleural fluid in patients with lymphocyte predominant pleural effusions, who don’t have a diagnosis of malignancy. If the level is above 50 U per liter, it is considered a positive exam. PCR may be sent in the same clinical scenario, and if Mycobacterium tuberculosis DNA is found, it is considered diagnostic.

If a patient has a metastatic adenocarcinoma, cytology will establish the diagnosis in >70% of cases. Yield is improved with sending both cell blocks and smears.


Choosing wisely: Over-utilized diagnostic tests

When diagnosing tuberculous pleural effusion, the yield of an AFB is 0-10%. It is 11-50% with culture, and 70% with pleural biopsy; other diagnostic tests are less invasive with higher yield; see above.

III. Management while the Diagnostic Process is Proceeding.

A. Management of Clinical Problem Pleural Effusions.

Early management should focus on:

Hemodynamic stabilization, including supportive care with supplemental O2.

Taking a good clinical history in order to manage the underlying cause while testing is obtained.

In a patient with pleuritic chest pain, hemoptysis, and shortness of breath out of proportion for the size of the pleural effusion, the diagnosis of PE should be suspected. Further diagnostic testing (i.e., D-dimer, CTA) should be considered, although the optimal approach to diagnose PE in the presence of pleural effusions is still not clear.

For suspected pneumonia or empyema, survival is increased with decreased time to antibiotics.


Management points not to be missed are:

Pneumothorax is the most common adverse event associated with thoracentesis. Some studies showed that the use of ultrasound guided thoracenthesis may decrease the risk for pneumothorax.

Removal of greater than 500 cc of pleural fluid may be associated with re-expansion pulmonary edema, and is more likely in patients with ipsilateral mediastinal shift seen on imaging.

If a patient has already been treated with diuretics, a pleural fluid sample may appear falsely exudative by Light’s criteria.

An empyema that is not treated with a therapeutic tap can form into a rind that can only be removed by thoracotomy. Please see criteria above for performing a therapeutic thoracentesis in a patient with empyema.

Malignant pleural effusions may also be treated with therapeutic taps and pigtail placement while chemotherapy or other treatments are initiated. Recurrent malignant effusions that require repeated thoracentesis may be treated with pleurodesis. Talc slurry, bleomycin and doxycycline may be used.

Talc is by far the least expensive method of achieving pleurodesis, but is associated with life-threatening respiratory failure in less than 1% of patients.

Avoid using tube thoracostomy with talk pleurodesis in patients with pleural effusions related to a hepatic hydrothorax given the high recurrence rate, as well as high morbidity and mortality.

IV. What's the evidence?

Light, Richard. “Pleural Effusion”. NEJM. vol. 346. June 20, 2002.

Mahajan, K. BMJ Case Report Feb 3 2016- Massive right pleural effusion leading to cardiac tamponade in absence of pericardial effusion: a rare presentation.

Saguil, A, Wyrick, A, Hallgren, J. “Diagnostic approach to pleural effusion”. Am Fam Physician.. vol. 90. 2014. pp. 99-104.

Fortin, M, Tremblay, A. “Pleural controversies: indwelling pleural catheter vs. pleurodesis for malignant pleural effusions”. J Thorac Dis. vol. 7. 2015 Jun. pp. 1052-7.

Akulian, J, Feller-Kopman, D. “The past, current and future of diagnosis and management of pleural disease”. J Thorac Dis. vol. 7. 2015 Dec. pp. S329-38.

Shojaee, S, Lee, HJ. “Thoracoscopy: medical versus surgical-in the management of pleural diseases”. J Thorac Dis. vol. 7. 2015 Dec. pp. S339-51.