DDx: Pleural Effusion Flashcards Preview

10 PULMONARY AND CRITICAL CARE MEDICINE > DDx: Pleural Effusion > Flashcards

Flashcards in DDx: Pleural Effusion Deck (35):
1

Dx: Pleural Effusion

DDx: Transudative or exudative

Dx:

Lateral Decubitus CRX - Horizontal meniscus 

Unexplained effusions larger than 1 cm should be aspirated. 

Thoracentesis is not necessary in patients who have small pleural effusions (<1 cm between the lung and chest wall on lateral chest radiograph) associated with heart failure, pneumonia, or heart surgery. 

Septations = loculated -> thoracostomy (+/- tPa) -> thoracotomy may be necessary

CHF - Diuresis -> thoracentesis if fails

Caution is advised when considering performing a thoracentesis in patients with severe coagulopathy, thrombocytopenia, hemodynamic compromise, or on mechanical ventilation. Pneumothorax is the major complication of thoracentesis.

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Parapneumonic Effusion

Occur in up to 50% of patients who are admitted to the hospital with bacterial pneumonia.

Tend to be small, free-flowing, sterile, and resolve with antibiotics (uncomplicated).  The presence of loculated (non-free-flowing) fluid predicts a poor response to treatment with antibiotics alone.

If bacteria persistently cross into the pleural space, patients can develop complicated parapneumonic effusions or empyemas.  Approximately 10% become complicated or progress to empyema.

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Empyema

An empyema, or infection in the pleural space, is suggested by the presence of a loculated effusion on upright and decubitus chest radiography or by obvious loculation on chest CT.

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Ddx: Transudative Effusions:

Transudative pleural effusions are caused by unbalanced hydrostatic forces and are associated more commonly with heart failure and cirrhosis and less commonly with nephrotic syndrome and constrictive pericarditis.

Atelectasis

Constrictive pericarditis

Duropleural fistula

Extravascular migration of central venous catheter

Heart failure

Hepatic hydrothorax

Hypoalbuminemia

Nephrotic syndrome

Peritoneal dialysis

Superior vena cava obstruction

Trapped lung

Urinothorax

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Atelectasis

Small effusion caused by increased negative intrapleural pressure; common in patients in the intensive care unit

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Constrictive pericarditis

Bilateral effusions with normal heart size; jugular venous distention present in 95% of cases

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Duropleural fistula

Cerebrospinal fluid in the pleural space; caused by trauma and surgery

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Extravascular migration of central venous catheter

With saline or dextrose infusion

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Heart failure

Most common cause of transudates; diuresis can increase pleural fluid protein and lactate dehydrogenase, resulting in discordant exudate; loss of hydrostatic pressure

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Hepatic hydrothorax

Occurs in 6% of patients with cirrhosis and clinical ascites; up to 20% do not have clinical ascites

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Hypoalbuminemia

Small bilateral effusions; edema fluid rarely isolated to pleural space; gastrosis nephrosis, cirrhosis

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Nephrotic syndrome

Typically small and bilateral effusions; unilateral effusion with chest pain suggests pulmonary embolism; loss of oncotic pressure

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Peritoneal dialysis

Small bilateral effusions common; rarely, large right effusion develops within 72 h of initiating dialysis

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Superior vena cava obstruction

Acute systemic venous hypertension

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Trapped lung

Unexpandable lung; unilateral effusion as a result of imbalance in hydrostatic pressures from remote inflammation

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Urinothorax

Unilateral effusion caused by ipsilateral obstructive uropathy

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Ddx: Exudative Pleural Effusions:

Light's criteria met

Inflammatory

Infectious - Pneumonia; (TB) - worldwide

Malignancy

Collagen vascular disease

Intra-abdominal processes

Hypothyroidism

Venous thromboembolic disease may cause either an exudative (particularly in the case of pulmonary infarction) or, less commonly, a transudative effusion. 

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Malignancy

A massive effusion, occupying the entire hemithorax, increases the likelihood of an underlying lung cancer or cancer involving the pleura (metastatic, mesothelioma).

Bilateral exudative effusions suggest malignancy but also occur in patients with pleuritis due to systemic lupus erythematosus and other collagen vascular diseases. 

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Collagen Vascular Disease

Bilateral exudative effusions suggest malignancy but also occur in patients with pleuritis due to systemic lupus erythematosus and other collagen vascular diseases. 

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Pleural Fluid Laboratory Studies:

Erythrocyte count

Leukocyte count

Neutrophils

Lymphocytes

pH

Glucose

Adenosine deaminase

Cytology

Culture

Useful in certain circumstances:

Hematocrit fluid to blood ratio

Amylase

Triglycerides

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Lights Criteria: Ratio of pleural fluid protein/LDH to serum protein/LDH:

"fluid comes first"

TpF/TPS  >0.5

Exudate   

LDHF/LDHS  >0.6

Exudate 

LDHF > 2/3 ULN

Transudate if all negative

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Ratio of pleural fluid lactate dehydrogenase (LDH) to serum LDH

≤0.6    Transudate

>0.6    Exudate

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Pleural fluid LDH

≤2/3 upper limit of normal for serum    Transudate

>2/3 upper limit of normal for serum    Exudate

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Erythrocyte count

>100,000/µL (100 x 109/L): malignancy, trauma (hemothroax), parapneumonic effusion, pulmonary embolism

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Leukocyte count

<1000/µL    Transudative

>10,000/µL (10 x 109/L): parapneumonic effusion (a noninfected effusion occurring in the pleural space adjacent to a bacterial pneumonia); acute pancreatitis; splenic infarction; and subphrenic, hepatic, and splenic abscesses.

>50,000/µL (50 x 109/L): complicated parapneumonic effusion or empyema (a parapneumonic effusion with persistent bacterial invasion) and empyema (established infection with pus in the pleural space) but occasionally occurs with acute pancreatitis and pulmonary infarction.

Malignant disease and tuberculosis typically present as a lymphocyte-predominant exudate. Additionally, although transudates may be blood-tinged, a grossly bloody effusion may be associated with cancer, tuberculosis, or trauma.

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Neutrophils

>50%: parapneumonic effusion, pulmonary embolism, abdominal disease

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Lymphocytes

>80%: tuberculosis (most common), malignancy (lymphoma), coronary artery bypass surgery, rheumatoid pleuritis, sarcoidosis

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pH

Normal pleural fluid pH is 7.60 to 7.66.

Exudates range from 7.30 to 7.45. 

Transudates are associated with a pleural fluid pH of 7.45 to 7.55.

A limited number of diagnoses are associated with a pleural fluid pH <7.20; the most common causes are complicated parapneumonic effusion or empyema, tuberculous pleurisy, esophageal rupture, rheumatoid pleuritis, and malignancy.

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Glucose

Glucose concentration in empyema is decreased due to the high metabolic activity of leukocytes (and/or bacteria) in the fluid.

Pleural fluid glucose <60 mg/dL is usually due to rheumatoid pleurisy, complicated parapneumonic effusion or empyema, malignant effusion, tuberculous pleurisy, lupus pleuritis, or esophageal rupture.  (Pleural glucose <30 mg/dL in particular suggests an empyema or rheumatic effusion.) 

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Adenosine deaminase

>40 U/L: tuberculosis (>90%), complicated parapneumonic effusion (30%) or empyema (60%), malignancy (5%)

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Cytology

Positive: malignancy (metastatic)

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Culture

Positive: infection

 

Gram stain + culture

- Fungi

- Bacteria

-TB

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Hematocrit fluid to blood ratio

≥0.5: hemothorax

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Amylase

Pleural fluid amylase should be measured only when pancreatic disease, esophageal rupture, or malignancy is considered.

 

35

Triglycerides

A chylous effusion (milky white fluid) is highly likely if the serum triglyceride level is >110 mg/dL (1.2 mmol/L). A chylous effusion (chylothorax) is commonly caused by leakage of lymph, rich in triglycerides, from the thoracic duct due to trauma or obstruction (eg, lymphoma).