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PostPosted: 14 Jun 2019 15:11 
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OVERVIEW
• The lungs are covered by two layers of serous membrane, the visceral pleural layer investing the lungs and the parietal pleura lining the walls of the thoracic cavity.
• The two layers enclose between them a potential space referred to as the pleural cavity or space.
• Normally the pleural space is small and contains a small amount of fluid (approximately 0.1 ml/kg).
• There are two pleural cavities, namely the right and left, one for each lung
• When there is excess fluid accumulation within the pleural space, it is referred to as pleural effusion
• Collection of pleural fluid is not a disease per se, but rather a feature of other underlying pathology including various disorders of the lung, pleura, and systemic conditions.

TYPES OF PLEURAL EFFUSION
Pleural effusions are classified into transudates and exudates.
• Transudative pleural effusion occurs due to alteration in hydrostatic forces to favour pleural fluid accumulation. Capillary permeability to proteins is normal. (Common causes - left ventricular failure (LVF), liver cirrhosis, hypoalbuminemia (nephrotic syndrome) and peritoneal dialysis).
• An exudative pleural effusion occurs when the pleural surface and/or the local capillary permeability are altered. (Common causes - cancer and parapneumonic effusions).
• Exudative effusions can also contain the following such as
Pus or turbid fluid – Empyema, infections
Blood – trauma, malignancy
Cholesterol – rheumatoid arthritis
Chyle – due to ruptured thoracic duct
Urine - hydronephrosis

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LIGHTS CRITERIA OF EXUDATIVE EFFUSION
• Pleural fluid protein concentration divided by serum protein level is greater than 0.5.
• Pleural fluid LDH level divided by level in serum more than 0.6.
• Pleural fluid LDH is more than two-thirds the upper limit of normal value in serum

COMMON CAUSES OF UNILATERAL EFFUSION
When a pleural effusion is large and unilateral, the following causes must be borne in mind
Simple exudate
o Infections – Tuberculosis, other bacterial infections, fungal, viral and parasitic (amebic)
o Malignancy – Lung cancer, mesothelioma, secondary deposits, lymphoma
o Connective tissue disorders – Rheumatoid arthritis, SLE
o Immunological – Sarcoidosis, Wegener’s granulomatosis
o Miscellaneous – Pulmonary embolism, uremia, post-bowel surgery, Meig’s syndrome, pancreatitis
o Iatrogenic – Radiation, Drugs (nitrofurantoin, amiodarone, phenytoin, methotrexate), esophageal sclerotherapy, misplacement of enteral feeding tube

Bloody effusion
o External trauma
o Surgical trauma
o Bleeding disorders
o Malignancy

Chylothorax
o Ruptured / injured thoracic duct
o Infiltration by tumor e.g. lymphoma
o Filariasis

APPROACH TO UNILATERAL PLEURAL EFFUSION
• An accurate drug history should be obtained during history taking. Although not common, several medications (see above) have been implicated in exudative pleural effusions. Discuss with a chest physician or your clinical pharmacist if necessary.
Aspiration should not be performed for bilateral effusions when the clinical picture is strongly suggestive of a transudate (see causes above) and should aim to treat the cause, unless there are atypical features and there is no response to therapy
• Fever suggests an infective etiology . History of pneumonia (cough fever) suggests parapneumonic effusion, either complicated (empyema or empyema-like) or uncomplicated.
• Older age, weight loss, and a smoking history are suggestive of malignant pleural effusion
• Obtain history of trauma or esophageal interventional procedures
Occupational history of asbestos exposure
Unilateral leg swelling and pain may indicate pulmonary embolism
• Physical findings include reduced tactile vocal fremitus, dullness on percussion, shifting dullness, and diminished or absent breath sounds. Large pleural effusions cause moderate to severe breathlessness and signs of mediastinal shift. Other findings may be related to the underlying cause
• Examination for lymphadenopathy, organomegaly and abdominal masses

INVESTIGATIONS
Posteroanterior (PA) and lateral chest x-rays should be requested to assess suspected pleural effusion. The posteroanterior (PA) chest x-ray detects presence of about 200 ml of pleural fluid. However, even 50 ml of pleural fluid can produce visible blunting of posterior costophrenic angle on a lateral chest x-ray.
• If chest radiography is inconclusive, CT scan and ultrasonography may be useful. CT scan can pick up effusions not apparent on plain radiography, as well as distinguish between pleural fluid and pleural thickening, and offer other clues to the possible cause. Ultrasound is more sensitive to detect pleural fluid septations than CT and can differentiate between benign and malignant effusions.
• In suspected exudate, a diagnostic pleural fluid sample should be obtained with a 50 ml syringe fine-bore (21G) needle
• Bedside ultrasound guidance improves the success rate of diagnostic aspiration and reduces complications (including pneumothorax) and is therefore advised.
• Appearance and color of pleural fluid may offer clues to the etiology
Pleural fluid should always be sent for analysis of protein, lactate dehydrogenase, Gram stain, differential count, microbial culture and cytology for malignant cells and amylase, cholesterol and triglyceride levels, tumor markers and pH
• If diagnosis is pointing towards malignancy, then histological confirmation is made by obtaining tissue sample through a bronchoscopy, or percutaneous pleural biopsy using video assisted thoracoscopy

The above approach will in most cases help to confirm the etiology so that definitive treatment can be planned.

MANAGEMENT OF UNILATERAL PLEURAL EFFUSION
• Parapneumonic effusion – therapeutic aspiration and treat the pneumonia
• Empyema – Urgent drainage and IV antibiotics
• Malignant effusion – Discuss with chest physician before draining. Therapeutic aspiration if patient is symptomatic
• Chylothorax (milky white) (e.g. post thoracic surgery / injury, haem malignancy) – Don’t drain until after discussion with chest physician. Therapeutic aspiration if patient symptomatic
• Rheumatoid arthritis/empyema (turbid fluid) – Sometimes distinguishing between rheumatoid effusion and empyema is difficult. Increased pleural fluid RA factor can aid in diagnosis
• Tuberculous effusions are treated with ATT
• Rheumatoid effusions and SLE associated effusions usually respond well to steroids and may resolve within 2 weeks
• Amebic pleural effusions are managed by metronidazole 800 mg three times daily for 5–10 days followed by diloxanide furoate 500 mg three times daily for 10 days
• Pleural hydatidosis is treated by surgical removal of cysts along with albendazole 400 mg once daily for a month before surgery
• Malignant effusions are managed with chemotherapy, radiotherapy, and rarely surgery
• Malignant chylothorax is usually managed by radiotherapy and/or chemotherapy.
Pleurodesis is the treatment of choice for recurrently filling effusions. Successful pleurodesis requires opposition of the visceral and parietal pleurae
Repeat thoracocentesis is usually reserved for pleural effusions that accumulate slowly following each thoracocentesis, patients who appear unlikely to survive beyond 1–3 months, and patients who cannot tolerate invasive procedures such as pleurodesis

KEY POINTS
Pleural effusion indicates some underlying pathology
Types include transudates and exudates
Transudates are usually bilateral
Thorough history and physical examination is essential
Unilateral effusions must be investigated with diagnostic aspiration and examination of pleural fluid
Imaging tests such as chest x-ray, USG and CT scan can provide information about possible cause
In about 20% cases, the cause remains unknown
Treatment includes treating the underlying cause and offering symptomatic relief in large effusions


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