Disorders of the Pleura
By: Anteneh A.[R1]
Pleural Effusion
The pleural space lies between the lung and the
chest wall.
Normally contains a very thin layer of fluid, which
serves as a coupling system.
A pleural effusion is present when there is an
excess quantity of fluid in the pleural space.
Pleural fluid accumulates when pleural fluid
formation exceeds pleural fluid absorption.
Con…
Normally, fluid enters the pleural space from the
capillaries in the parietal pleura and is removed via
the lymphatics in the parietal pleura.
Fluid can enter the pleural space from interstitial
spaces of the lung via the visceral pleura.
From the peritoneal cavity via small holes in the
diaphragm.
The lymphatics have the capacity to absorb 20
times more fluid than is formed normally.
Con…
Accordingly, a pleural effusion may develop
when there is:
Excess pleural fluid formation (from the
interstitial spaces of the lung, the parietal
pleura, or the peritoneal cavity). or
Decreased fluid removal by the lymphatics.
Diagnostic Approach
Patients suspected of having PE should undergo
chest imaging to diagnose its extent.
An effort should be made to determine the cause.
The first step is to determine whether the effusion is
a transudate or an exudate.
A transudative PE occurs when systemic factors that
influence the formation and absorption are altered.
The leading causes of transudative PE in the US are
left ventricular failure and cirrhosis.
Con…
An exudative PE occurs when local factors that
influence the formation and absorption are altered.
The leading causes of exudative PE are bacterial
pneumonia, malignancy, viral infection, and PTE.
The primary reason for making this differentiation
is that additional diagnostic Ixs are indicated for
exudative effusions to define the local cause.
Con….
Transudative and exudative PEs are distinguished
by measuring pleural fluid LDH and protein.
Exudative PEs meet at least one of the following
criteria, whereas transudative PEs meet none:
1. Pleural fluid protein/serum protein >0.5
2. Pleural fluid LDH/serum LDH >0.6
3. Pleural fluid LDH more than two-thirds the
normal upper limit for serum.
These criteria misidentify ~25% of transudates as
exudates.
Con…
Ifone or more of the exudative criteria are meet and
the patient is clinically thought to have a condition
producing a transudative effusion:
The difference between the protein levels in the
serum and the pleural fluid should be measured.
If this gradient is >31 g/L (3.1 g/dL), the exudative
categorization by these criteria can be ignored b/c
almost all such patients have a transudative PE.
One criterion to be met to define an exudate:
Two-test rule
Pleural fluid cholesterol greater than 45 mg/dL
Pleural fluid LDH > 0.45 times the ULN serum
LDH
Three-test rule
Pleural fluid protein >2.9 g/dL (29 g/L)
Pleural fluid cholesterol > 45 mg/dL
Pleural fluid LDH > 0.45 times the ULN serum
LDH
Con…
Ifa patient has an exudative pleural effusion, the
following tests should be obtained:
Description of the appearance of the fluid
Glucose level
Cell count with differential
Microbiologic studies
Cytology
Causes of pleural effusions
Transudative Pleural Effusions
1. Congestive heart failure
2. Cirrhosis
3. Nephrotic syndrome
4. Peritoneal dialysis
5. Superior vena cava obstruction
6. Myxedema
7. Urinothorax
Con…
Exudative Pleural Effusions
1. Neoplastic diseases
A. Metastatic disease
B. Mesothelioma
2. Infectious diseases
C. Bacterial infections
D. Tuberculosis
E. Fungal infections
F. Viral infections
G. Parasitic infections
Con…
3. Pulmonary embolization
4. Gastrointestinal disease
A. Esophageal perforation
B. Pancreatic disease
C. Intraabdominal abscesses
D. Diaphragmatic hernia
E. After abdominal surgery
F. Endoscopic variceal sclerotherapy
G. After liver transplant
Con…
5. Collagen vascular diseases
A. Rheumatoid pleuritis
B. Systemic lupus erythematosus
C. Drug-induced lupus
D. Sjögren syndrome
E. Granulomatosis with polyangiitis (Wegener)
F. Churg-Strauss syndrome
Con…
6. Post-coronary artery bypass surgery
7. Asbestos exposure
8. Sarcoidosis
9. Uremia
10. Meigs’ syndrome
11. Yellow nail syndrome
Con…
12. Drug-induced pleural disease
A. Nitrofurantoin
B. Dantrolene
C. Methysergide
D. Bromocriptine
E. Procarbazine
F. Amiodarone
G. Dasatinib
Con…
13. Trapped lung
14. Radiation therapy
15. Post-cardiac injury syndrome
16. Hemothorax
17. Iatrogenic injury
18. Ovarian hyperstimulation syndrome
19. Pericardial disease
20. Chylothorax
Effusion Due to Heart Failure
The most common cause of pleural effusion is left
ventricular failure.
The effusion occurs because the increased
amounts of fluid in the lung interstitial spaces exit
in part across the visceral pleura.
This overwhelms the capacity of the lymphatics in
the parietal pleura to remove fluid.
Con…
Indications of diagnostic thoracentesis in
effusions of HF :
1. If the effusions are not bilateral
2. If the effusions are not comparable in size.
3. If the patient is febrile.
4. If the patient has pleuritic chest pain.
5. If the effusion persists despite therapy.
Con…
Otherwise the patient’s heart failure is treated.
If the effusion persists despite therapy, a diagnostic
thoracentesis should be performed.
A pleural fluid N-terminal pro-brain natriuretic
peptide (NT-proBNP) >1500 pg/mL is virtually
diagnostic that the effusion is secondary to CHF.
Hepatic Hydrothorax
Pleural effusions occur in ~5% of patients with
cirrhosis and ascites.
The predominant mechanism is the direct
movement of peritoneal fluid through small
openings in the diaphragm into the pleural
space.
The effusion is usually right-sided and
frequently is large enough to produce severe
dyspnea.
Parapneumonic Effusion
Are effusions associated with bacterial
pneumonia, lung abscess, or bronchiectasis.
Are probably the most common cause of
exudative pleural effusion in the US.
Empyema refers to a grossly purulent effusion.
If the free fluid separates the lung from the chest
wall by >10 mm, a therapeutic thoracentesis
should be performed.
Con…
Indications of chest tube in increasing
order of importance include:
1. Loculated pleural fluid
2. Pleural fluid pH <7.20
3. Pleural fluid glucose <3.3 mmol/L (<60
mg/dL)
4. Positive Gram stain or culture of the
pleural fluid
5. Presence of gross pus in the pleural
space
Steps
Firstdo therapeutic paracentesis.
Then, chest tube with fibrinolytic agent (e.g.,
TPA, 10 mg) and deoxyribonuclease (5 mg)
is next step.
Then, performing a thoracoscopy with the
breakdown of adhesions.
Decortication should be considered when
these measures are ineffective.
Effusion Secondary to Malignancy
Malignant PE 20 to metastatic disease are the second
most common type of exudative PE.
The three tumors that cause ~75% of all malignant
PEs are lung carcinoma, breast carcinoma, and
lymphoma.
Most patients complain dyspnea, which is frequently
out of proportion to the size of the effusion.
The pleural fluid is an exudate, and its glucose level
may be reduced if the tumor burden in the pleural
space is high.
Con…
The diagnosis usually is made via cytology of the
pleural fluid.
If the initial cytologic examination is negative,
thoracoscopy is the best next procedure if
malignancy is strongly suspected.
At the time of thoracoscopy, pleural abrasion should
be performed to effect a pleurodesis.
Patients with a malignant pleural effusion are treated
symptomatically for the most part.
Con…
To relive the dyspnea with therapeutic
thoracentesis do:
(1) Insertion of a small indwelling catheter or
(2) Tube thoracostomy with the instillation of
a sclerosing agent (doxycycline 500 mg).
Effusion Secondary to Pulmonary Embolization
The diagnosis most commonly overlooked in the
differential diagnosis of a patient with an
undiagnosed pleural effusion is pulmonary embolism.
Dyspnea is the most common symptom.
The pleural fluid is almost always an exudate.
The diagnosis is established by spiral CT scan or
pulmonary arteriography.
If the PE increases in size after anticoagulation, the
patient probably has recurrent emboli or another
complication, such as a hemothorax or a pleural
infection.
Tuberculous Pleuritis
In many parts of the world, it is the most common
cause of an exudative PE.
Tuberculous PEs usually are associated with
primary TB.
Thought to be due primarily to a hypersensitivity
reaction to tuberculous protein in the pleural space.
Patients with TB pleuritis present with fever, weight
loss, dyspnea, and/or pleuritic chest pain.
The pleural fluid is an exudate with predominantly
small lymphocytes.
Con…
The diagnosis is established by demonstrating
high levels of TB markers in the pleural fluid.
Adenosine deaminase >40 IU/L or interferon
γ>140 pg/mL.
Alternatively, the diagnosis can be established by
culture of the pleural fluid, needle biopsy of the
pleura, or thoracoscopy.
The recommended treatments of pleural and
pulmonary TB are identical.
Effusion Secondary to Viral Infection
Are responsible for a sizable percentage of
undiagnosed exudative pleural effusions.
In many series, no diagnosis is established for
~20% of exudative effusions.
These effusions resolve spontaneously with no
long term residua.
If the patient is improving clinically with out
treatment, consider it.
Chylothorax
A chylothorax occurs when the thoracic duct is
disrupted and chyle accumulates in the pleural
space.
The most common cause of chylothorax is trauma
(most frequently thoracic surgery).
It also may result from tumors in the mediastinum.
Patients with chylothorax present with dyspnea, and
a large pleural effusion on CXR.
Thoracentesis reveals milky fluid, and biochemical
analysis reveals a TG level that exceeds 1.2 mmol/L
(110 mg/dL).
Con…
The treatment of choice for most chylothorax is
insertion of a chest tube plus the administration of
octreotide.
If these modalities fail, percutaneous
transabdominal thoracic duct blockage effectively
controls most chylothoraces.
An alternative treatment is ligation of the thoracic
duct.
Patients with chylothoraxes should not undergo
prolonged tube thoracostomy with chest tube
drainage because this will lead to malnutrition and
immunologic incompetence.
Hemothorax
When a diagnostic thoracentesis reveals bloody pleural
fluid, a hematocrit should be obtained on the pleural
fluid.
If the hematocrit is more than one half of that in the
peripheral blood, considered to have a hemothorax.
Most hemothoraxes are the result of trauma.
Other causes include rupture of a blood vessel or tumor.
Most patients with hemothorax should be treated with
tube thoracostomy.
If hemorrhage exceeds 200 mL/h, consider angiographic
coil embolization, thoracoscopy or thoracotomy.
Miscellaneous Causes of PE
There are many other causes of pleural effusion.
Key features of some of these conditions are as follows:
If the pleural fluid amylase level is elevated, consider
esophageal rupture or pancreatic disease is likely.
If the patient is febrile, has predominantly
polymorphonuclear cells in the pleural fluid, and has no
pulmonary parenchymal abnormalities, an
intraabdominal abscess should be considered.
The diagnosis of an asbestos pleural effusion is one of
exclusions.
Benign ovarian tumors can produce ascites and a
pleural effusion (Meigs’ syndrome)
References
Harrison’s principle of internal medicine
20th ed.
