"Physiologically, the pleural cavities normally contain approximately 0.1–0.2 mL/kg or 5-15 mL of serous pleural fluid 6. Any process which results in more fluid forming than can be absorbed will produce a pleural effusion."
"Volume (mL) = 0.365 × b3 – 4.529 × b2 + 159.723 × b – 88.377 where b = the maximum depth of the effusion measured in the axial plane in centimetres 16"
"Volume (mL) = 0.365 × b3 – 4.529 × b2 + 159.723 × b – 88.377 where b = the maximum depth of the effusion measured in the axial plane in centimetres 16"
"Volume (mL) = 0.365 × b3 – 4.529 × b2 + 159.723 × b – 88.377 where b = the maximum depth of the effusion measured in the axial plane in centimetres 16"
"Volume (mL) = 0.365 × b3 – 4.529 × b2 + 159.723 × b – 88.377 where b = the maximum depth of the effusion measured in the axial plane in centimetres 16"
"Mergo's formula 18: Volume (mL) = d2 x l, where d = greatest depth of the effusion on a single CT image in centimetres, l = greatest craniocaudal length of the effusion (coronal or sagittal plane) in centimetres"
"With a slight rounding, maximum effusion depths of 2, 4, 6, 8, and 10 cm represent volumes of approximately 200, 500, 800, 1100, and 1400 mL of pleural effusion, respectively. Various online calculators are also available for this purpose 17."
"If simple fluid, then the term hydrothorax may be employed, although this is rarely used (other than in combination terms, e.g. hydropneumothorax)."
"Both PA and AP erect films are insensitive to small amounts of fluid. Features include:"
"Both PA and AP erect films are insensitive to small amounts of fluid. Features include:"
"Volume (mL) = 0.365 × b3 – 4.529 × b2 + 159.723 × b – 88.377 where b = the maximum depth of the effusion measured in the axial plane in centimetres 16"
"Mergo's formula 18: Volume (mL) = d2 x l, where d = greatest depth of the effusion on a single CT image in centimetres, l = greatest craniocaudal length of the effusion (coronal or sagittal plane) in centimetres"
Expected headings
"Transudates vs exudates"
"Transudate"
"Exudate"
"Differential white cell count"
"Polymorphonuclear pleural effusion"
"Eosinophilic pleural effusion"
"Lymphocytic pleural effusion"
"Chest radiograph (lateral decubitus)"
"Chest radiograph (erect)"
"Chest radiograph (supine)"
"Volume quantification"
""Pleural effusion" is commonly used as a catch-all term to describe any abnormal accumulation of fluid in the pleural cavity. The lack of specificity is mainly due to the limitations of the imaging modality. Given that most effusions are detected by x-ray, which generally cannot distinguish between fluid types, the fluid in question may be simple (transudative) fluid, blood, pus, chylous fluid, etc."
"With a slight rounding, maximum effusion depths of 2, 4, 6, 8, and 10 cm represent volumes of approximately 200, 500, 800, 1100, and 1400 mL of pleural effusion, respectively. Various online calculators are also available for this purpose 17."
"As the accumulation of fluid in the pleural space occurs in a broad range of disparate clinical scenarios, no single demographic is affected; rather, the epidemiology will match that of the underlying condition. However, it is probably safe to say that, as congestive cardiac failure and malignancy are some of the most common causes, older patients would be over-represented."
"Chest radiographs are the most commonly used examination to assess for the presence of pleural effusion; however, it should be noted that on a routine erect chest x-ray, as much as 250-600 mL of fluid is required before it becomes evident 6. A lateral decubitus projection is most sensitive, able to identify even a small amount of fluid. At the other extreme, supine projections can mask large quantities of fluid."
"Precise volume of the effusion can be calculated using proper volumetry; however, in clinical practice, this labour-intensive but accurate quantification is rarely needed. Various formulas have thus been proposed, which allow estimation of the effusion volume using simple calliper measurements:"
"strange or atypical configurations of pleural fluid can be due to either adhesions (i.e. loculated effusion) or underlying atelectasis; the latter is more likely to change with patient positioning 12"
"There are many causes of pleural effusion that are broadly split into transudates and exudates. This categorisation relies upon the biochemical analysis of aspirated pleural fluid according to Light’s criteria 5,24:"
"Large amounts of fluid can be present on supine films with minimal imaging changes, as the fluid is dependent and collects posteriorly. There is no meniscus, and only a veil-like increased density of the hemithorax may be visible. It is therefore especially difficult to identify similarly sized bilateral effusions, as the density of the lungs will be similar."
"Differential white cell count of the pleural aspirate is also important, resulting in pleural effusions with mainly granulocytes, eosinophils or lymphocytes 14."
"CT scanning is excellent at detecting small amounts of fluid and is also often able to identify the underlying intrathoracic causes (e.g. malignant pleural deposits or primary lung neoplasms) as well as subdiaphragmatic diseases (e.g. subdiaphragmatic abscess)."
"The treatment of pleural effusions is usually targeted to the underlying condition (e.g. congestive cardiac failure or malignancy). Symptomatic patients with large effusions may be treated by therapeutic aspiration (thoracentesis)."