Some Causes of Pleural Effusion* 

Transudate

Heart failure

Bilateral effusions in 81%; right-sided in 12%; left-sided in 7% †

With left ventricular failure, there is increased interstitial fluid, which crosses the visceral pleura and enters the pleural space

Cirrhosis with ascites (hepatic hydrothorax)

Right-sided effusions in 70%; left-sided in 15%; bilateral in 15% ‡

Ascitic fluid migration to the pleural space through diaphragmatic defects

Effusion present in about 5% of patients with clinically apparent ascites

Hypoalbuminemia

Uncommon

Bilateral effusions in > 90%

Intravascular oncotic pressure decreases, which leads to the pleural effusions

Associated with edema or anasarca elsewhere

Nephrotic syndrome

Usually bilateral effusions; commonly subpulmonic

Decreased intravascular oncotic pressure plus hypervolemia causing transudation into the pleural space

Hydronephrosis

Retroperitoneal urine dissection into the pleural space, causing urinothorax

Constrictive pericarditis

Increases in right- and left-sided IV hydrostatic pressure

In some patients, accompanied by massive anasarca and ascites due to a mechanism similar to that for hepatic hydrothorax

Atelectasis

Increases negative intrapleural pressure

Peritoneal dialysis

Mechanism similar to that for hepatic hydrothorax

Pleural fluid with characteristics similar to dialysate

Trapped lung

Encasement with fibrous peel increasing negative intrapleural pressure

May be exudative or borderline exudate

Systemic capillary leak syndrome

Rare

Accompanied by anasarca and pericardial effusion

Myxedema (hypothyroidism)

Effusion present in about 5%

Usually transudate if pericardial effusion is also present, due to elevated hydrostatic pressures; either transudate or exudate if pleural effusion is isolated

Exudate

Pneumonia (parapneumonic effusion)

May be uncomplicated (not frankly infected), or complicated with loculations or septations, or purulent (empyema)

Thoracentesis necessary to differentiate

Pleural fluid chemistry typically shows very high LDH (eg, > 900 U/L [15 microkat/L]) and low glucose

Cancer

Most commonly lung cancer, breast cancer, or lymphoma but possible with any tumor metastatic to pleurae

Typically causing dull, aching chest pain

Pulmonary embolism

Effusion present in about 30%:

Almost always exudative; bloody in < 50%

Pulmonary embolism suspected when dyspnea is disproportionate to size of effusion

Viral infection

Effusion usually small with or without parenchymal infiltrate

Predominantly systemic symptoms rather than pulmonary symptoms

Coronary artery bypass surgery

Effusions left-sided or larger on the left in 73%; bilateral and equal in 20%; right-sided or larger on the right in 7%

> 25% of the hemithorax filled with fluid 30 days postoperatively in 10% of patients

Bloody effusions related to postoperative bleeding likely to resolve

Nonbloody effusions likely to recur; etiology unknown but probably with an immunologic basis

Tuberculosis (TB)

Effusion usually unilateral and ipsilateral to parenchymal infiltrates if present

Effusion due to hypersensitivity reaction to TB protein

Pleural fluid TB cultures positive in < 20%

Typically, pleural fluid glucose level low (in the low nearly normal range) compared with serum glucose

Sarcoidosis

Effusion in 1–2%

Extensive parenchymal sarcoid and often extrathoracic sarcoid

Pleural granulomas in many patients without effusion

Pleural fluid predominantly lymphocytic

Uremia

Effusion in about 3%

In > 50%, symptoms secondary to effusion: Most commonly fever (50%), chest pain (30%), cough (35%), and dyspnea (20%)

Diagnosis of exclusion

Infradiaphragmatic abscess

Causes sympathetic subpulmonic effusion

Neutrophils predominant in pleural fluid

pH and glucose normal

HIV infection

Many possible etiologic factors: Pneumonias (parapneumonic), including Pneumocystis jirovecii pneumonia, other opportunistic infections, TB, and pulmonary Kaposi sarcoma

Rheumatoid arthritis

Effusion typically in older men with rheumatoid nodules and deforming arthritis

Must differentiate from parapneumonic effusion (both characterized by low glucose, low pH, and high LDH)

Systemic lupus erythematosus (SLE)

Effusion possibly first manifestation of SLE

Common with drug-induced SLE

Diagnosis established by serologic tests of blood, not of pleural fluid

Medications

Ovarian hyperstimulation syndrome

Effusion developing 7–14 days after hCG injection

Effusion right-sided in 52%; bilateral in 27%

Pancreatitis

Acute: Effusion present in about 50%: Bilateral in 77%; left-sided in 16%; right-sided in 8%

Effusion due to transdiaphragmatic transfer of the exudative inflammatory fluid and diaphragmatic inflammation

Chronic: Effusion due to sinus tract from pancreatic pseudocyst through diaphragm into pleural space

Predominantly chest symptoms rather than abdominal symptoms

Patients presenting with cachexia that resembles cancer

Superior vena cava syndrome

Effusion usually caused by blockage of intrathoracic venous and lymphatic flow by cancer or thrombosis in a central catheter

May be an exudate or a chylothorax

Esophageal rupture

Patients extremely sick

Medical emergency

Morbidity and mortality due to infection of the mediastinum and pleural space

Benign asbestos pleural effusion

Effusion occurring > 30 years after initial exposure

Frequently asymptomatic

Tends to come and go

Diagnosis of exclusion; must rule out mesothelioma

Benign ovarian tumor (Meigs syndrome)

Mechanism similar to that for hepatic hydrothorax

Surgery sometimes indicated for patients with ovarian mass, ascites, and pleural effusion

For diagnosis, disappearance of ascites and effusion postoperatively required

Yellow nail syndrome

Triad of pleural effusion, lymphedema, and yellow nails, sometimes appearing decades apart

Pleural fluid with relatively high protein but low lactate dehydrogenase

Tendency for effusion to recur

No pleuritic chest pain