A Pleural effusion is an excessive accumulation of fluid in the pleural space. It can be detected clinically when there is 500 mL or more present, and by plain Chest X-ray when there is more than 300 mL. Massive effusions are most commonly malignant in origin. A pleural effusion may be asymptomatic (if small) or cause breathlessness. The typical physical signs and chest X-ray appearances are shown in the pictures below.
Pleural Effusion In X-rays And DIagrams
Pleural effusion is excess fluid that accumulates between the two pleural layers, the fluid-filled space that surrounds the lungs. Excessive amounts of such fluid can impair breathing by limiting the expansion of the lungs during ventilation. | Source
Pleural effusion is usually diagnosed on the basis of medical history and physical exam, and confirmed by chest x-ray. Once accumulated fluid is more than 300 ml, | Source
there are usually detectable clinical signs in the patient, such as decreased movement of the chest on the affected side, stony dullness to percussion over the fluid, diminished breath sounds on the affected side | Source
decreased vocal resonance and fremitus (though this is an inconsistent and unreliable sign), and pleural friction rub. | Source
Above the effusion, where the lung is compressed, there may be bronchial breathing and egophony. In large effusion there may be tracheal deviation away from the effusion. | Source
A systematic review (2009) published as part of the Rational Clinical Examination Series in the Journal of the American Medical Association (JAMA) showed that dullness to conventional percussion was most accurate for diagnosing pleural effusion (summ | Source
while the absence of reduced tactile vocal fremitus made pleural effusion less likely (negative likelihood ratio, 0.21; 95% confidence interval, 0.12–0.37). | Source
A pleural effusion will show up as an area of whiteness on a standard posteroanterior X-ray. Normally the space between the two layers of the lung, the visceral pleura and the parietal pleura, cannot be seen. | Source
A pleural effusion infiltrates the space between these layers. Because the pleural effusion has a density similar to body fluid or water, it can be seen on radiographs. Since the effusion has greater density than the rest of the lung, it will gravita | Source
The pleural effusion behaves according to basic fluid dynamics, conforming to the shape of the lung and chest cavity. If the pleural cavity contains both air and fluid, then the fluid will have a "fluid level" that is horizontal instead of conforming | Source
Chest radiographs acquired in the lateral decubitus position (with the patient lying on his side) are more sensitive and can pick up as little as 50 ml of fluid. | Source
At least 300 ml of fluid must be present before upright chest films can pick up signs of pleural effusion (e.g., blunted costophrenic angles). | Source
Definitions of the terms "transudate" and "exudate" are the source of much confusion. Briefly, transudate is produced through pressure filtration without capillary injury while exudate is "inflammatory fluid" leaking between cells. | Source
Transudative pleural effusions are defined as effusions that are caused by systemic factors that alter the pleural equilibrium, or Starling forces. | Source
The components of the Starling forces–hydrostatic pressure, permeability, oncotic pressure (effective pressure due to the composition of the pleural fluid and blood)–are altered in many diseases, e.g., left ventricular failure, renal failure, hepatic | Source
Exudative pleural effusions, by contrast, are caused by alterations in local factors that influence the formation and absorption of pleural fluid (e.g., bacterial pneumonia, cancer, pulmonary embolism, and viral infection). | Source
An accurate diagnosis of the cause of the effusion, transudate versus exudate, relies on a comparison of the chemistries in the pleural fluid to those in the blood, using Light's criteria | Source
The sensitivity and specificity of Light's criteria for detection of exudates have been measured in many studies and are usually reported to be around 98% and 80% respectively. | Source
This means that although Light's criteria are relatively accurate, twenty percent of patients that are identified by Light's criteria as having exudative pleural effusions actually have transudative pleural effusions. | Source
Therefore, if a patient identified by Light's criteria as having an exudative pleural effusion appears clinically to have a condition that usually produces transudative effusions, additional testing is needed. In such cases albumin levels in blood an | Source
1. All X-ray photos here are from DFM E-Group, in the photo and X-ray section.
2. Notes and explanations: Wikipedia, Essentials of Clinical Medicine by Kumar and Clark's, Medicinenet and Mayor's Clinic.