Pleural Effusion

MedTutor Class on Pleural Effusion

Why does fluid accummulate in the pleural space?
How much fluid is needed for a pleural effusion to be detectable clinically? To be detected on chest x-ray?

Student: ‎1. Pleural effusion pathophysiology can be seen from two point of views in regards to it's type of effusion which is either transudative or exudative. Transudative type resolves around two principles which is increased hydrostatic pressure… or reduce plasma oncotic pressure. This two pathophysiology will cause transudation of fluids into the pleural space. Eg : heart failure, liver failure, renal failure. Exudative type is associated with injuries to the lung or pleural surface itself. To differentiate this two type, findings from amount of protein either <25g/L for transudate or >35g/L for exudative. Light's criteria need to be used if between 25 - 35 g/L.
2. Clinically detected should be from 300ml - 500ml
3. 75ml is needed to blunt the posterior costophrenic angle while 300ml to blunt the lateral costophrenic angleSee More
Student: In order to be detectable clinically, there'd have to be 500ml of fluid or more while for it to be detectable in chest x-ray, there should be 300ml of fluid or more present. In some articles however, it is said that fluid as little as 25ml may be seen in an erect PA chest x-ray.

Moderator: A pleural effusion occurs either because of an imbalance between the osmotic and hydrostatic pressures in the blood or because of inflammation of the pleura (pleuritis). The inflammation of the pleura may be caused by infective causes (bacteria, viruses) or non-infective causes (eg trauma, pulmonary infarct). Exactly how much fluid must be present in the pleura in order for it to be detectable clinically or radiologically is not very important for our practice but one should have a general idea about it. The normal pleural space may contain about 5ml of fluid according to some references; about 300ml of fluid is said to be needed for it to be detectable clinically. When a pleural effusion causes only blunting of the costophrenic angle in a chest x-ray, one can assume that there is about 100 to 150ml of fluid there.

The main symptom of a pleural effusion is breathlessness. Chest discomfort can also occur. Cough, if present, in a patient with a pleural effusion, usually means that there is something affecting the underlying lung. We normally expect the trachea to be pushed to the opposite side in a large unilateral pleural effusion. What should you suspect when that does not happen, or, the trachea is shifted instead to the same side as the effusion?

Student: If the trachea is pushed towards the site of effusion the lung has either collapsed or undergone fibrosis?
Student: or can be an underlying lung carcinoma which causes pleural effusion at the same time
Student: what about loculated pleural effusions? will it be detected clinically with the same amount as generalised pleural effusions??? just curious about this …
Student: If the trachea is not push to the other side of the lung or instead pulled to the effusion side we must suspect that there is underlying lung collapse or fibrosis that pull the lung toward the same side. The underlying lung Ca can cause obstruction and subsequently lung collapse as well.

Moderator: In a large pleural effusion, when the trachea is not shifted to the opposite side as expected, an underlying collapse or fibrosis of the lung beneath the pleural effusion should be suspected. Small effusions, whether loculated or not, will not be expected to cause tracheal deviation. Large effusions, even if loculated, can cause tracheal shift.

One of the first things you need to determine when faced with a pleural effusion is whether the effusion is a transudate or an exudate. Light’s criteria which uses the ratio of fluid protein to serum protein or the ratio of fluid LDH to serum LDH is normally used to make this distinction. Light’s criteria may misclassify about 20 percent of transudates as exudates. Do all pleural effusions need to be aspirated? How much fluid can be aspirated during a single sitting? What is the significance of chest discomfort and cough when these occur while aspirating pleural fluid?

Moderator: A diagnostic aspiration (aspirating a small amount of fluid) may be necessary in most pleural effusions unless one is confident, clinically, that the effusion is a transude secondary to congestive heart failure or the nephrotic syndrome. Therapeutic aspiration is not needed when the pleural effusion is small and is secondary to congestive cardiac failure or to viral pleurisy. When pleural effusions are secondary to pneumonia, many of these effusions will resolve with the treatment of the pneumonia. A guideline is: When the pH of the fluid in an effusion associated with pneumonia is more than 7.3, it indicates an uncomplicated effusion and does not need therapeutic aspiration. When the pH is less than 7.3, it means that there is a lot of lactate in the fluid (implying a high degree of metabolic activity). The implication of this is that the effusion is either an empyema or is malignant. Such effusions must be removed.

The volume of fluid that can be safely aspirated from pleural effusions in a single sitting: 1000 to 1500ml. When more than this is aspirated at one time, there is the danger of re-expansion pulmonary edema. When there is chest discomfort during aspiration, it usually means that the underlying lung is not expanding well. Cough can occur during aspiration when the needle hits against the lung.

The gross appearance of the pleural fluid can sometimes give a clue to its etiology. What does it mean when:
a. The pleural fluid is purulent or turbid?
b. The pleural fluid is milky?
c. The pleural fluid is bloody?
And, when the pleural fluid is bloody, how do you distinguish between a hemothorax (bleeding into the pleural space) and a hemorrhagic effusion?

Student: If the pleural fluid is purulent or turbid, it is due to the presence of inflammatory cells and debris. And therefore we should suspect an empyema. If it is milky, it is due to the presence of chyle. In chylous effusions we should look for the cause such as lymphoma, surgical trauma or other tumours. A blood pleural fluid is suggestive of malignancy, pulmonary embolism and trauma.
The hematocrit of the fluid will help differentiate between hemothorax and hemorrhagic effusion. If the hematocrit of the fluid exceeds half the hematocrit of the peripheral blood, we should suspect a hemothorax.

Student: Purulent or turbid pleural fluid : suspect pleural empyema (pus) associated with pneumonia, abscesses such as lung and hepatic and posttraumatic.
Milky pleural fluid : suspect chylous effusion associated with neoplastic (lymphoma) or traumatic damage to lymphatic (thoracic) duct. The effusion is high in triglycerides. On the other hand, chyliform effusions resemble chylous effusions but there is low triglycerides and high in cholesterol where release of cholesterol is thought to be due to lyse RBCs and neutrophils in long-standing effusion associated with tuberculosis, poorly treated empyema and others when absorption is blocked by thickened pleura. Besides that, there are situations where patient receiving parenteral nutrition and superior vena cava is penetrated, fat globules can accumulate in pleural space.
Bloody pleural fluid : suspect trauma, malignancy, pulmonary embolism.
I agree with Khine. Hemothorax is defined as pleural fluid with a hematocrit >50% of the blood hematocrit hence the hematocrit level will distinguish between hemothorax and haemorrhagic effusion.

Student: from this study done by villena et al published in the chest journal, almost half of the bloody effusions are due to neoplasm, 11% due to neoplastic effusions, 13.5% malignant effusions and 24% by mesothelioma and the commonest cause of malignant effusions is mesothelioma and adenocarcinoma. other benign causes are parapneumonic and posttraumatic (as in a surgical setting) and less common causes can be found in patients who underwent CABG or had postcardiac injury syndrome,acute aortic dissection, thoracic vascular disruption, pancreatitis, haemangiomatosis and endometriosis to name a few. Because a RBC count as low as 5000 - 10,000 /ul, can cause a pleural effusion to turn red, the finding of blood-tinged fluid per se has little diagnostic value (usually from needle trauma). to add on, chylothorax can also be due to liver cirrhosis, tuberculosis, or idiopathic and pseudochylothorax secondary to rheumatoid arthritis.

Moderator: The gross appearance of pleural fluid gives important clues. A purulent fluid indicates empyema and will need chest tube drainage. A milky appearance to the pleural fluid is suggestive of elevated triglyceride content and may indicate damage to the thoracic duct. A bloody pleural effusion is often due to malignancies. To distinguish hemorrhagic effusion from a hemothorax, do a hematocrit of the fluid. If the fluid hematocrit is more than 50 percent of the blood hematocrit, it is a hemothorax.

Estimation of the pleural fluid glucose is useful in some cases because pleural effusions associated with rheumatoid arthritis, malignancies, tuberculosis and lupus erythematosus will have low fluid glucose content. Empyemas will also have low glucose content.

If the fluid is an exudate, cell count, gram staining, culture and cytology will need to be done. Special tests that are sometimes done are: Adenosine deaminase activity and interferon gamma concentration for diagnosis of tuberculous pleural effusions.

When should a pleural biopsy be done for those with pleural effusions? When should we consider doing pleurodesis?

Student: a pleural biopsy should be done if FEME of from the pleural tap shows that the effusion is exudative. exudative effusions may be due to malignancy, TB, SLE, rheumatoid arthritis, pneumonia, pulmonary embolism, viral infections, asbestosis, myxedema, uremia, drugs, or idiopathic. the top two causes for an exudative effusion are malignancy and TB! Pleurodesis should be considered if the patients suffers from recurrent pleural effusions or recurrent pneumothorax. it offers symptomatic relief. pleurodesis can be performed either using chemical agents (eg. bleomycin) or surgically (via thoracotomy/thoracostomy)

Moderator: A pleural biopsy is usually necessary only when the diagnosis of tuberculosis or malignancy is being considered for a pleural effusion and the diagnosis cannot be confirmed in any other way. Pleurodesis is to be considered as a therapeutic measure when pleural effusions due to malignancy recur rapidly. Pleurodesis can be done using talc powder, doxycycline, or drugs like cyclophosphamide and bleomycin.

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