Pleural effusion

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• Pleural effusion

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• Definition
• A pleural effusion is an excessive accumulation
  of fluid in the pleural space. It can be detected
  on X-ray when 300 mL or more of fluid is present
  and clinically when 500 mL or more is present.
• The chest X-ray appearances range from the
  obliteration of the costophrenic angle to dense
  homogeneous shadows occupying part or all of the
  hemithorax. Fluid in the fissures may resemble an
  intrapulmonary mass.

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Pleural Effusion on CXR
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Etiology

• Pleural fluid accumulates when pleural fluid
  formation exceeds pleural fluid absorption.
  Normally, fluid enters the pleural space from the
  capillaries in the parietal pleura and is removed
  via the lymphatics situated in the parietal
  pleura.
• Fluid can also enter the pleural space from the
  interstitial spaces of the lung via the visceral
  pleura or from the peritoneal cavity via small
  holes in the diaphragm.
• The lymphatics have the capacity to absorb 20
  times more fluid than is normally formed.
• 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 when there
  is decreased fluid removal by the lymphatics.

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Diagnostic Approach

• When a patient is found to have a pleural
  effusion, an effort should be made to determine
  the cause. The first step is to determine whether
  the effusion is a transudate or an exudate.
• 1-A transudative pleural effusion occurs when
  systemic factors that influence the formation and
  absorption of pleural fluid are altered.
• The leading causes of transudative pleural
  effusions are lt. ventricular failure
  cirrhosis.

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• 2-An exudative pleural effusion occurs when local
  factors that influence the formation absorption
  of pleural fluid are altered.
• The leading causes of exudative pleural effusions
  are bacterial pneumonia, malignancy, viral
  infection, pulmonary embolism.
• The primary reason to make this differentiation
  is that additional diagnostic procedures are
  indicated with exudative effusions to define the
  cause of the local disease.

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• Transudative exudative pleural effusions are
  distinguished by measuring the lactate
  dehydrogenase (LDH) protein levels in the
  pleural fluid. Exudative pleural effusions meet
  at least one of the following criteria, whereas
  transudative pleural effusions meet none
• pleural fluid LDH/serum LDH gt0.6
• pleural fluid protein/serum protein gt0.5
• pleural fluid LDH more than two-thirds normal
  upper limit for serum

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• The above criteria misidentify 25 of
  transudates as exudates. If one or more of the
  exudative criteria are met and the patient is
  clinically thought to have a condition producing
  a transudative effusion, the difference between
  the protein levels in the serum the pleural
  fluid should be measured.
• If this gradient is greater than 3.1 g/dL. the
  exudative categorization by the above criteria
  can be ignored because almost all such patients
  have a transudative pleural effusion.

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• If a patient has an exudative pleural effusion,
  the following tests on the pleural fluid should
  be obtained description of the fluid, glucose
  level, differential cell count, microbiologic
  studies cytology.

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Effusion Due to Heart Failure

• The most common cause of pleural effusion is lt.
  ventricular failure. The effusion occurs because
  the increased amounts of fluid in the lung
  interstitial spaces exit in part across the
  visceral pleura. This overcomes the capacity of
  the lymphatics in the parietal pleura to remove
  fluid.
• Isolated right-sided pleural effusions are more
  common than left-sided effusions in heart
  failure.

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• A diagnostic thoracentesis should be performed if
  the effusions are not bilateral comparable in
  size, if the patient is febrile, or if the
  patient has pleuritic chest pain, to verify that
  the patient has a transudative effusion.
• The patient is best treated with diuretics. If
  the effusion persists despite diuretic therapy, a
  diagnostic thoracentesis should be performed.

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Hepatic Hydrothorax

• Pleural effusions occur in 5 of patients with
  cirrhosis 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 frequently
  is large enough to produce severe dyspnea.

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Parapneumonic Effusion

• Parapneumonic effusions are associated with
  bacterial pneumonia, lung abscess, or
  bronchiectasis. Empyema refers to a grossly
  purulent effusion.
• Patients with aerobic bacterial pneumonia
  pleural effusion present with an acute febrile
  illness consisting of chest pain, sputum
  production, leukocytosis.
• Patients with anaerobic infections present with a
  subacute illness with weight loss, a brisk
  leukocytosis, mild anemia, a history of some
  factor that predisposes them to aspiration.

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• The possibility of a parapneumonic effusion
  should be considered whenever a patient with a
  bacterial pneumonia is initially evaluated.
• If the free fluid separates the lung from the
  chest wall by gt10 mm, a therapeutic thoracentesis
  should be performed. Factors indicating the
  likely need for a procedure more invasive than a
  thoracentesis include loculated pleural fluid,
  positive Gram stain or culture of the pleural
  fluid, or the presence of gross pus in the
  pleural space.

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• If the fluid recurs after the initial therapeutic
  thoracentesis, if any of the above
  characteristics are present, a repeat
  thoracentesis should be performed.
• If the fluid cannot be completely removed with
  the therapeutic thoracentesis, consideration
  should be given to inserting a chest tube
  instilling a fibrinolytic (e.g., streptokinase,
  250,000 units) or performing thoracoscopy with
  the breakdown of adhesions.
• Decortication should be considered when the above
  are ineffective.

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Effusion Secondary to Malignancy

• Malignant pleural effusions secondary to
  metastatic disease are the second most common
  type of exudative pleural effusion.
• The three tumors that cause 75 of all
  malignant pleural effusions are lung carcinoma,
  breast carcinoma lymphoma.
• Patients complain of dyspnea, which is
  frequently out of proportion to the size of the
  effusion.
• The pleural fluid is an exudate, its glucose
  level may be reduced if the tumor burden in the
  pleural space is high.
• The diagnosis is usually made via cytology of the
  pleural fluid needle biopsy of the pleura .

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Treatment

• The only symptom that can be attributed to the
  effusion itself is dyspnea.
• If the patient's lifestyle is compromised by
  dyspnea if the dyspnea is relieved with a
  therapeutic thoracentesis, then one of the
  following procedures should be considered
• Insertion of a small indwelling catheter.
• Tube thoracostomy with the instillation of a
  sclerosing agent such as doxycycline, 500 mg.

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Mesothelioma

• Malignant mesotheliomas are primary tumors that
  arise from the mesothelial cells that line the
  pleural cavities most are related to asbestos
  exposure.
• Patients with mesothelioma present with chest
  pain shortness of breath.
• The chest radiograph reveals a pleural effusion,
  generalized pleural thickening, a shrunken
  hemithorax.
• Thoracoscopy or open pleural biopsy is usually
  necessary to establish the diagnosis.
• Chest pain should be treated with opiates
  shortness of breath with oxygen and/or opiates.

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Tuberculous Pleuritis

• In many parts of the world, the most common cause
  of an exudative pleural effusion is tuberculosis
  (TB).
• Tuberculous pleural effusions are usually
  associated with primary TB are thought to be
  due primarily to a hypersensitivity reaction to
  tuberculous protein in the pleural space.
• Patients with tuberculous pleuritis present with
  fever, weight loss, dyspnea /or pleuritic chest
  pain.
• The pleural fluid is an exudate with
  predominantly small lymphocytes.

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• The diagnosis is established by demonstrating
  high levels of TB markers in the pleural fluid
  (adenosine deaminase gt 40 IU/L, interferon gt
  140 pg/mL, or positive polymerase chain reaction
  (PCR) for tuberculous DNA).
• Alternatively, the diagnosis can be established
  by culture of the pleural fluid, needle biopsy of
  the pleura, or thoracoscopy.
• The recommended treatment of pleural pulmonary
  TB is identical .

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Chylothorax

• A chylothorax occurs when the thoracic duct is
  disrupted chyle accumulates in the pleural
  space.
• The most common cause of chylothorax is trauma,
  but it also may result from tumors in the
  mediastinum.
• Patients with chylothorax present with dyspnea,
  a large pleural effusion is present on the
  chest radiograph.
• Thoracentesis reveals milky fluid biochemical
  analysis reveals a triglyceride level that
  exceeds 110mg/dL.

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• Patients with chylothorax no obvious trauma
  should have a lymphangiogram a mediastinal CT
  scan to assess the mediastinum for lymph nodes.
• The treatment of choice for most chylothoraces is
  insertion of a chest tube.
• If these modalities fail, a pleuroperitoneal
  shunt should be placed unless the patient has
  chylous ascites.
• Patients with chylothoraces should not undergo
  prolonged tube thoracostomy with chest tube
  drainage because this will lead to malnutrition
  and immunologic incompetence.

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Hemothorax

• When a diagnostic thoracentesis reveals bloody
  pleural fluid, a hematocrit should be obtained on
  the pleural fluid. If the hematocrit is more than
  half of that in the peripheral blood, the patient
  is considered to have a hemothorax.
• Most hemothoraces 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, which allows continuous
  quantification of bleeding. If the pleural
  hemorrhage exceeds 200 mL/h, consideration should
  be given to thoracoscopy or thoracotomy.

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Miscellaneous Causes of Pleural Effusion

• 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,
  the diagnosis of 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.
• Benign ovarian tumors can produce ascites a
  pleural effusion (Meigs' syndrome).

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• Several drugs can cause pleural effusion the
  associated fluid is usually eosinophilic
  eg,(Nitrofurantoin, Bromocriptine Amiodarone).
• Pleural effusions commonly occur following
  coronary artery bypass surgery.
• Other medical manipulations that induce pleural
  effusions include abdominal surgery radiation
  therapy liver, lung, or heart transplantation
  or the intravascular insertion of central lines.