PLEURAL EFFUSIONS
Anatomy and Dynamics of pleural Fluid
Pleura:
A thin membrane consisting of a single layer of mesothelial cells supported by a
network of connective and fibroelastic tissue, lymphatics, vessel and investing the lungs and
lining the cavities of the hemithoraces.The mesothelial cells are rich in microvilli, and their
most important function is to deliver glycoproteins rich in hyaluronic acid with decrease
friction between lung and chest wall.
Parietal pleura: Receiving its blood supply from the systemic circulation and
containing sensory nerve ending.
Visceral pleura: Receiving its blood supply from the low pressure pulmonary
circulation and containing no sensory nerve fibers.
Pleural space: A potential space that is situated between parietal and visceral pleura
and normally filled with 5-l0ml of serous fluid.
Pleural fluid is formed primarily from the parietal pleura, and part of its turnover
depends on the same starling forces that govern vascular and interstitial fluid exchange.
The parietal pleura has a hydrostatic pressure similar to that of the systemic circulation
(30 cm H2O) whereas that of the visceral pleura depends on the pulmonary circulation
(10 cm H2O).0ncotic pleasure is similar in both(25 cm H2O),but the preassure within
the pleural cavity is affected by the gravity gradient Thus the pleural space is
heterogeneous with a nondependent portion where starling forces favor outpouring of
fluid to the cavity and into parenchymal capillaries. The stomas or "lacuna," present
over the parietal surface of the low mediastinum, low chest wall, and diaphragm, seem
to empty into lymphatics. These subpleural lymphatics represent the major pathway for
liquid and solute drainage. Alterations of this formation-resorption mechanism
frequently result in the accumulation of pleural fluid. Increases in hydrostatic forces or
decreases in oncotic pressures result in low protein "transudates". Increased
outpouring by "capillaries or cells and/or blocking of lymphatics results in high protein
"exudates".
Parietal Pleural
Hydrostatic
pressure(30)
Pleural Space
Visceral Pleural
11
Pressureof pleural
space
8 (5)
34
Permeability of
systemic
circulation(34)
Permeabilityof pleural
fluid (8)
5+8+30-34=9
34-(5+8+11)=10
The mechanisms that lead to accumulation of pleural fluid
l.Increased hydrostatic pressure in microvascular circulation.(congestive heart failure)
2.Decreased oncotic pressure in microvascular circulation.(severe hypoalbuminemia)
3 .Decreased pressure in the pleural space.(complete lung collapse)
4.Increased permeability of the microvascular circulation.(pneumonia)
5.Impaired lymphatic drainage from the pleural space, (malignant effusion)
6.Movement of fluid from peritoneal space.(ascites)
Common causes of pleural effusions
Transudates
1.Generalized salt and water retention, e.g. congestive heart failure, nephrotic
syndrome, hypoalbuminemia.
2.Ascites, e.g., cirrhosis, meigs' syndrome, peritoneal dialysis.
3.Vascular obstruction, e.g., superior vena cava obstruction.
4.Tumor
Exudates
1.Infectious diseases, e.g., TB, bacterial pneumonias, and other infectious
diseeses.
2.Tumor
3.Pulmonary infarction
4.Rheumatic diseases
Hemorrhagic effusion
1.Trauma
2.Tumor
3.Pulmonary infarction
4.TB
5. Spontaneous pneumothorax
Chylous effusion
1.Trauma
2.Tumor
3.TB
4.Thrombosis of the left subclavian vein
Empyema
;
1.TB
2.Pulmonary infection
3.Trauma
4.Esophageal rupture
Bilateral effusion
1 .Generalized salt and water retention e.g., congestive heart failure,
nephritic syndrome.
2.Ascites.
.
•
3.Pulmonaiy infarction
4.Lupus erythematosus: rheumatoid arthritis
5.Tumor
6.TB
TB is the most common cause of pleural effusion , especially in young
people. Malignant pleural effusion is frequently met in aged people today.
p1eura1 transudation is most commonly caused by congestive heart
failure.
Pleurisy
Pleurisy is inflammation of the pleura due to either an infectious or
noninfectious cause and it may occur with or with or without p1eura1
effusion.
Dry or fibrinous pleurisy: without pleural effusion
Humid or exudative pleurisy: with pleural effusion. Dry pleurisy is often
followed by humid pleurisy.
Diagnostic procedures
(1) History and physical examination
Pleural pain, dyspnea, tachypnea, mild outward bulging of the
intercostal spaces, decreased tactile fremitus, dullness or flatness,
decreased transmission of breath and vocal sounds in the area of the
effusion, and occasionally pleural friction sound in its early stage (dry
pleurisy).
(2)Roentgenographic examination
Blunting of the normally sharp costophyrenic angle, a concave shadow
with its highest margin along the pleural surface, shift of the mediastinum
and the trachus toward the normal side.
(3) Ultrasonic examination
To localize a small pleural effusion and determine the correct site for
performance of a thoracentesis.
(4)Thoracentesis
To aspirate the effusion for laboratory examination:
Appearance, specific gravity, protein content, cell counts, glucose,
LDH lipid content. Rheumatoid factor (RF), Adenisine deaminase (ADA),
Lupus pleuritis (LE) cells. Gram stain and culture, and cytologic
examination, etc.
(5) Pleural biopsy
To obtain a specimen for histologic examination and culture.
Differentiation of specific types of pleural effusion
1. Transudate and exudate
Tab. 1. Differentiation of transudate and exudate
Transudate
Cause
non-inflammatory
Appearance
light yellow, serous
Transparency
clear or slightly cloudy
Specific Gravity
<1.018
Coagulability
unable
Revalta test
negative
Protein content
<25g/L
Pleural P./Serum P.
<0.5
LDH
<200IU/L
Pleural L./SerumL.
<0.6
Exudate
inflammatory, tumor,physical or
chemical irritation
yellow, purulent
turdid often
>1.018
able
positive
>25g/L
>0.5
>200IU/L
>0.6
2. Bloody Effusion
Bloody effusion is exudative and blood-tinted (Serosanguineous) fluid
may be produced by as few as 5000 red blood cells/ mm3. Malignancy,
trauma, and pulmonary infarction are the most frequent caused of bloody
plural effusion, although congestive heart .failure and infection can
produce serosanguinenous effusions
3. Chylous Effusion
Often caused by trauma granulomatous disease or tumor and with the fluid
having a characteristic milky white .appearance and high fat content.
Treatment
Treatment for many pleural effusions, whether transudates or exudates
is primarily for the underlying pulmonary or systemic disease: aspiration
of fluid is usually indicated only to establish the diagnosis and is
therapeutically unnecessary except to relieve dyspnea from a large
effusion.
Tuberculous pleural Effusion
TB remains the most common cause of pleural effusion in young
people.
Etiology: Tubercle bacillus
Pathogenesis: Host hypersensitivity to tubercular protein in pleural
tubercles (delayed hypersensitivity)
Pathology: congestiopn and edema of the pleura:
Cellular infiltration and an increase in vascular permeability: a fibrinous,
cellular exudate in pleural surfaces (dry pleurisy); and finally a significant
accumulation of fluid which is rich in plasma protein and contains cell
with predominance of lymphocyte.
Clinical Manifestations
Generalized symptoms of toxicity of TB: Fever, high sweat, fatigue
and weight loss, etc.
„
Those of pleural effusion: pleuritic pain, short breath and dyspnea, etc.
Pleural fluid is exudative and usually reveals lymphocytosis. Rarely
pleural fluid is blood stained
The PPD or OT test usually positive.
Diagnosis:
Based on aforementioned findings and histologic examination for
granulomas and culture of material obtained at biopsy of the pleura,
together with Culture of pleural fluid.
Treatment
(1).Standard antituberculous regimens (long course of antituberculous
chemotherapy or short course therapy)
(2).Administration of corticosteroid during the first several weeks of
treatment.
(3). Thoracentesis
Empyema
Thick purulent fluid with more than 100,000 cells per cubic millimeter
or fluid wlth pH values less than or equal to 7.20 should be treated as a
presumptive empyema.
The general objectives of therapy of empyema are the elimination of both
the systemic and local infection-the evacuation of pus, the obliteration of
the pleural space and reexpansion of the lung, and the restoration of
normal pulmonary function.
Treatment of acute empyema
1 Control of infection( systemic and local)
2.Repeated thoracentesis or drainage of the empyema.
Chronic empyema is primarily treated operatively, i.e. decortication.
Operative therapy is also indicated in empyema with associated
bronchopleural fistula or with the ipsilateral ruined lung.