pleural space The pleural cavity, pleural space, or interpleural space is the potential space between the pleurae of the pleural sac that surrounds each lung. A small amount of serous pleural fluid is maintained in the pleural cavity to enable lubrication bet ...

potential space In anatomy, a potential space is a space between two adjacent structures that are normally pressed together (directly apposed). Many anatomic spaces are potential spaces, which means that they are potential rather than realized (with their realiz ...

pleural fluid The pleural cavity, pleural space, or interpleural space is the potential space between the pleurae of the pleural sac that surrounds each lung. A small amount of serous pleural fluid is maintained in the pleural cavity to enable lubrication be ...

parietal pleura The pulmonary pleurae (''sing.'' pleura) are the two opposing layers of serous membrane overlying the lungs and the inside of the surrounding chest walls. The inner pleura, called the visceral pleura, covers the surface of each lung and dips be ...

lymphatic Lymph (from Latin, , meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues to ...

vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often di ...

visceral pleura The pulmonary pleurae (''sing.'' pleura) are the two opposing layers of serous membrane overlying the lungs and the inside of the surrounding chest walls. The inner pleura, called the visceral pleura, covers the surface of each lung and dips b ...

hydrostatic Fluid statics or hydrostatics is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body "fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an imme ...

serous fluid In physiology, serous fluid or serosal fluid (originating from the Medieval Latin word ''serosus'', from Latin ''serum'') is any of various body fluids resembling serum, that are typically pale yellow or transparent and of a benign nature. The fl ...

hydrothorax Hydrothorax is a type of pleural effusion in which transudate accumulates in the pleural cavity. This condition is most likely to develop secondary to congestive heart failure, following an increase in hydrostatic pressure within the lungs. More ...

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...

hemothorax A hemothorax (derived from hemo- lood+ thorax hest plural ''hemothoraces'') is an accumulation of blood within the pleural cavity. The symptoms of a hemothorax may include chest pain and difficulty breathing, while the clinical signs may incl ...

pus Pus is an exudate, typically white-yellow, yellow, or yellow-brown, formed at the site of inflammation during bacterial or fungal infection. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collection ...

pyothorax Pleural empyema is a collection of pus in the pleural cavity caused by microorganisms, usually bacteria. Often it happens in the context of a pneumonia, injury, or chest surgery. It is one of the various kinds of pleural effusion. There are three ...

pleural empyema Pleural empyema is a collection of pus in the pleural cavity caused by microorganisms, usually bacteria. Often it happens in the context of a pneumonia, injury, or chest surgery. It is one of the various kinds of pleural effusion. There are three ...

chyle Chyle (from the Greek word χυλός ''chylos'', "juice") is a milky bodily fluid consisting of lymph and emulsified fats, or free fatty acids (FFAs). It is formed in the small intestine during digestion of fatty foods, and taken up by lymph v ...

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellular ...

urinothorax Urinothorax (''pl''. urinothoraces) is defined as urine in the fluid-filled cavity that surrounds the lungs. It is usually caused by obstructive uropathy. It is mainly diagnosed by analyzing the pleural fluid. Treatment involves treating the ...

pneumothorax A pneumothorax is an abnormal collection of air in the pleural space between the lung and the chest wall. Symptoms typically include sudden onset of sharp, one-sided chest pain and shortness of breath. In a minority of cases, a one-way valve i ...

air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...

hydropneumothorax Hydropneumothorax is defined as the presence of both air and fluid within the pleural space. An upright chest x-ray will show air fluid levels. The horizontal fluid level is usually well defined and extends across the whole length of one of the he ...

Serous fluid In physiology, serous fluid or serosal fluid (originating from the Medieval Latin word ''serosus'', from Latin ''serum'') is any of various body fluids resembling serum, that are typically pale yellow or transparent and of a benign nature. The fl ...

hydrothorax Hydrothorax is a type of pleural effusion in which transudate accumulates in the pleural cavity. This condition is most likely to develop secondary to congestive heart failure, following an increase in hydrostatic pressure within the lungs. More ...

Blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...

haemothorax A hemothorax (derived from hemo- lood+ thorax hest plural ''hemothoraces'') is an accumulation of blood within the pleural cavity. The symptoms of a hemothorax may include chest pain and difficulty breathing, while the clinical signs may incl ...

Chyle Chyle (from the Greek word χυλός ''chylos'', "juice") is a milky bodily fluid consisting of lymph and emulsified fats, or free fatty acids (FFAs). It is formed in the small intestine during digestion of fatty foods, and taken up by lymph v ...

Pus Pus is an exudate, typically white-yellow, yellow, or yellow-brown, formed at the site of inflammation during bacterial or fungal infection. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collection ...

pyothorax Pleural empyema is a collection of pus in the pleural cavity caused by microorganisms, usually bacteria. Often it happens in the context of a pneumonia, injury, or chest surgery. It is one of the various kinds of pleural effusion. There are three ...

empyema An empyema () is a collection or gathering of pus within a naturally existing anatomical cavity. For example, pleural empyema is empyema of the pleural cavity. It must be differentiated from an abscess, which is a collection of pus in a newly fo ...

Urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellular ...

urinothorax Urinothorax (''pl''. urinothoraces) is defined as urine in the fluid-filled cavity that surrounds the lungs. It is usually caused by obstructive uropathy. It is mainly diagnosed by analyzing the pleural fluid. Treatment involves treating the ...

transudative Transudate is extravascular fluid with low protein content and a low specific gravity (< 1.012). It has low nucleated cell counts (less than 500 to 1000 /microliter) and the primary cell types are heart failure and

cirrhosis Cirrhosis, also known as liver cirrhosis or hepatic cirrhosis, and end-stage liver disease, is the impaired liver function caused by the formation of scar tissue known as fibrosis due to damage caused by liver disease. Damage causes tissue rep ...

. Nephrotic syndrome, leading to the loss of large amounts of

albumin Albumin is a family of globular proteins, the most common of which are the serum albumins. All the proteins of the albumin family are water-soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins ...

in urine and resultant low albumin levels in the blood and reduced colloid osmotic pressure, is another less common cause of pleural effusion. Pulmonary emboli were once thought to cause transudative effusions, but have been recently shown to be exudative. The mechanism for the exudative pleural effusion in pulmonary thromboembolism is probably related to increased permeability of the

capillaries A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body: ...

in the lung, which results from the release of cytokines or inflammatory mediators (e.g.

vascular endothelial growth factor Vascular endothelial growth factor (VEGF, ), originally known as vascular permeability factor (VPF), is a signal protein produced by many cells that stimulates the formation of blood vessels. To be specific, VEGF is a sub-family of growth factors, ...

) from the

platelet Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby i ...

-rich blood clots. The excessive interstitial lung fluid traverses the

visceral pleura The pulmonary pleurae (''sing.'' pleura) are the two opposing layers of serous membrane overlying the lungs and the inside of the surrounding chest walls. The inner pleura, called the visceral pleura, covers the surface of each lung and dips b ...

and accumulates in the

pleural space The pleural cavity, pleural space, or interpleural space is the potential space between the pleurae of the pleural sac that surrounds each lung. A small amount of serous pleural fluid is maintained in the pleural cavity to enable lubrication bet ...

. Conditions associated with transudative pleural effusions include:Galagan et al. Color Atlas of Body Fluids. CAP Press, Northfield, 2006 *

Congestive heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, ...

* Liver

cirrhosis Cirrhosis, also known as liver cirrhosis or hepatic cirrhosis, and end-stage liver disease, is the impaired liver function caused by the formation of scar tissue known as fibrosis due to damage caused by liver disease. Damage causes tissue rep ...

* Severe hypoalbuminemia * Nephrotic syndrome * Acute atelectasis *

Myxedema Myxedema is a term used synonymously with severe hypothyroidism. However, the term is also used to describe a dermatological change that can occur in hyperthyroidism and (rare) paradoxical cases of hypothyroidism. In this latter sense, myxedema ...

*

Peritoneal dialysis Peritoneal dialysis (PD) is a type of dialysis which uses the peritoneum in a person's abdomen as the membrane through which fluid and dissolved substances are exchanged with the blood. It is used to remove excess fluid, correct electrolyte pro ...

* Meigs's syndrome * Obstructive uropathy * End-stage kidney disease

Exudative

When a pleural effusion has been determined to be

exudative An exudate is a fluid emitted by an organism through pores or a wound, a process known as exuding or exudation. ''Exudate'' is derived from ''exude'' 'to ooze' from Latin ''exsūdāre'' 'to (ooze out) sweat' (''ex-'' 'out' and ''sūdāre'' 'to ...

, additional evaluation is needed to determine its cause, and

amylase An amylase () is an enzyme that catalyses the hydrolysis of starch (Latin ') into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. Foods that contain large amounts of ...

,

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...

, pH and cell counts should be measured. * Red blood cell counts are elevated in cases of bloody effusions (for example after heart surgery or hemothorax from incomplete evacuation of blood). * Amylase levels are elevated in cases of

esophageal rupture Esophageal rupture is a rupture of the esophageal wall. Iatrogenic causes account for approximately 56% of esophageal perforations, usually due to medical instrumentation such as an endoscopy or paraesophageal surgery. In contrast, the term Boerh ...

, pancreatic pleural effusion, or

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

. * Glucose is decreased with cancer, bacterial infections, or rheumatoid pleuritis. * pH is low in

empyema An empyema () is a collection or gathering of pus within a naturally existing anatomical cavity. For example, pleural empyema is empyema of the pleural cavity. It must be differentiated from an abscess, which is a collection of pus in a newly fo ...

(<7.2) and maybe low in cancer. * If cancer is suspected, the pleural fluid is sent for

cytology Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living an ...

. If cytology is negative, and cancer is still suspected, either a

thoracoscopy Thoracoscopy is a medical procedure involving internal examination, biopsy and/or resection/drainage of disease or masses within the pleural cavity, usually with video assistance. Thoracoscopy may be performed either under general anaesthe ...

, or needle biopsy of the pleura may be performed. *

Gram staining In microbiology and bacteriology, Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. The name comes from the Danish bac ...

and culture should also be done. * If

tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, i ...

is possible, examination for '' Mycobacterium tuberculosis'' (either a Ziehl–Neelsen or

Kinyoun stain The Kinyoun method or Kinyoun stain (cold method), developed by Joseph J. Kinyoun, is a procedure used to staining (biology), stain acid-fast species of the bacterial genus ''Mycobacterium''. It is a variation of a method developed by Robert Koch in ...

, and mycobacterial cultures) should be done. A

polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies (complete or partial) of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it (or a part of it) ...

for tuberculous DNA may be done, or

adenosine deaminase Adenosine deaminase (also known as adenosine aminohydrolase, or ADA) is an enzyme () involved in purine metabolism. It is needed for the breakdown of adenosine from food and for the turnover of nucleic acids in tissues. Its primary function ...

or

interferon gamma Interferon gamma (IFN-γ) is a dimerized soluble cytokine that is the only member of the type II class of interferons. The existence of this interferon, which early in its history was known as immune interferon, was described by E. F. Wheeloc ...

levels may also be checked. The most common causes of exudative pleural effusions are bacterial

pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severi ...

, cancer (with

lung cancer Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissues of the lung. Lung carcinomas derive from transformed, malign ...

,

breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a r ...

, and

lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enla ...

causing approximately 75% of all malignant pleural effusions), viral infection, and

pulmonary embolism Pulmonary embolism (PE) is a blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream ( embolism). Symptoms of a PE may include shortness of breath, chest pain particularly upon breathin ...

. Another common cause is after heart surgery when incompletely drained blood can lead to an inflammatory response that causes exudative pleural fluid. Conditions associated with exudative pleural effusions: *

Parapneumonic effusion A parapneumonic effusion is a type of pleural effusion that arises as a result of a pneumonia, lung abscess, or bronchiectasis. There are three types of parapneumonic effusions: uncomplicated effusions, complicated effusions, and empyema. Uncomp ...

due to

pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severi ...

* Malignancy (either lung cancer or metastases to the pleura from elsewhere) * Infection (empyema due to bacterial pneumonia) * Trauma * Pulmonary infarction *

Pulmonary embolism Pulmonary embolism (PE) is a blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream ( embolism). Symptoms of a PE may include shortness of breath, chest pain particularly upon breathin ...

* Autoimmune disorders *

Pancreatitis Pancreatitis is a condition characterized by inflammation of the pancreas. The pancreas is a large organ behind the stomach that produces digestive enzymes and a number of hormones. There are two main types: acute pancreatitis, and chronic pancr ...

* Ruptured esophagus ( Boerhaave's syndrome) * Rheumatoid

pleurisy Pleurisy, also known as pleuritis, is inflammation of the membranes that surround the lungs and line the chest cavity ( pleurae). This can result in a sharp chest pain while breathing. Occasionally the pain may be a constant dull ache. Other sy ...

* Drug-induced lupus

Other/ungrouped

Other causes of pleural effusion include

tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, i ...

(though stains of pleural fluid are only rarely positive for

acid-fast Acid-fastness is a physical property of certain bacterial and eukaryotic cells, as well as some sub-cellular structures, specifically their resistance to decolorization by acids during laboratory staining procedures. Once stained as part of a sam ...

bacilli, this is the most common cause of pleural effusions in some developing countries),

autoimmune In immunology, autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other normal body constituents. Any disease resulting from this type of immune response is termed an "autoimmune disease". ...

disease such as systemic lupus erythematosus, bleeding (often due to chest trauma), chylothorax (most commonly caused by trauma), and accidental infusion of fluids. Less common causes include esophageal rupture or pancreatic disease, intra-abdominal abscesses,

rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are invol ...

, asbestos pleural effusion,

mesothelioma Mesothelioma is a type of cancer that develops from the thin layer of tissue that covers many of the internal organs (known as the mesothelium). The most common area affected is the lining of the lungs and chest wall. Less commonly the lining ...

, Meigs's syndrome (ascites and pleural effusion due to a benign

ovarian tumor Ovarian tumors, or ovarian neoplasms, are tumors arising from the ovary. They can be benign or malignant (ovarian cancer). They consist of mainly solid tissue, while ovarian cysts contain fluid. Histopathologic classification Ovarian tumors are ...

), and

ovarian hyperstimulation syndrome Ovarian hyperstimulation syndrome (OHSS) is a medical condition that can occur in some women who take fertility medication to stimulate egg growth, and in other women in very rare cases. Most cases are mild, but rarely the condition is severe and c ...

. Pleural effusions may also occur through medical or surgical interventions, including the use of medications (pleural fluid is usually

eosinophilic Eosinophilic (Greek suffix -phil-, meaning ''loves eosin'') is the staining of tissues, cells, or organelles after they have been washed with eosin, a dye. Eosin is an acidic dye for staining cell cytoplasm, collagen, and muscle fibers. ''E ...

), coronary artery bypass surgery, abdominal surgery, endoscopic variceal sclerotherapy,

radiation therapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radi ...

,

liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...

or lung transplantation, insertion of ventricular shunt as a treatment method of hydrocephalus, and intra- or extravascular insertion of central lines.

Pathophysiology

Pleural fluid is secreted by the parietal layer of the

pleura The pulmonary pleurae (''sing.'' pleura) are the two opposing layers of serous membrane overlying the lungs and the inside of the surrounding chest walls. The inner pleura, called the visceral pleura, covers the surface of each lung and dips b ...

and reabsorbed by the lymphatics in the most dependent parts of the parietal pleura, primarily the diaphragmatic and mediastinal regions. Exudative pleural effusions occur when the pleura is damaged, e.g., by trauma, infection, or malignancy, and transudative pleural effusions develop when there is either excessive production of pleural fluid or the resorption capacity is reduced. Light's criteria can be used to differentiate between exudative and transudative pleural effusions.

Diagnosis

A pleural effusion is usually diagnosed on the basis of

medical history The medical history, case history, or anamnesis (from Greek: ἀνά, ''aná'', "open", and μνήσις, ''mnesis'', "memory") of a patient is information gained by a physician by asking specific questions, either to the patient or to other peo ...

and

physical exam In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally consists of a series of questions about the patie ...

, and confirmed by a chest X-ray. Once accumulated fluid is more than 300 mL, there are usually detectable

clinical sign Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showin ...

s, such as decreased movement of the chest on the affected side, dullness to percussion over the fluid, diminished

breath sounds Respiratory sounds, also known as lung sounds or breath sounds, refer to the specific sounds generated by the movement of air through the respiratory system. These may be easily audible or identified through auscultation of the respiratory system ...

on the affected side, decreased vocal resonance and

fremitus Fremitus is a vibration transmitted through the body. In common medical usage, it usually refers to assessment of the lungs by either the vibration intensity felt on the chest wall (''tactile fremitus'') and/or heard by a stethoscope on the chest ...

(though this is an inconsistent and unreliable sign), and

pleural friction rub A pleural friction rub, or simply pleural rub, is an audible medical sign present in some patients with pleurisy and other conditions affecting the chest cavity. It is noted by listening to the internal sounds of the body, usually using a stethosc ...

. Above the effusion, where the lung is compressed, there may be bronchial breathing sounds and

egophony Egophony (British English, aegophony) is an increased resonance of voice sounds heard when auscultating the lungs, often caused by lung consolidation and fibrosis. It is due to enhanced transmission of high-frequency sound across fluid, such as in ...

. A large effusion there may cause

tracheal The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends from the la ...

deviation away from the effusion. A systematic review (2009) published as part of the Rational Clinical Examination Series in the Journal of the American Medical Association showed that dullness to conventional percussion was most accurate for diagnosing pleural effusion (summary positive

likelihood ratio The likelihood function (often simply called the likelihood) represents the probability of random variable realizations conditional on particular values of the statistical parameters. Thus, when evaluated on a given sample, the likelihood functi ...

, 8.7; 95% confidence interval, 2.2–33.8), 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).

Imaging

A pleural effusion appears as an area of whiteness on a standard posteroanterior chest X-ray. Normally, the space between the visceral pleura and the parietal pleura cannot be seen. A pleural effusion infiltrates the space between these layers. Because the pleural effusion has a density similar to water, it can be seen on radiographs. Since the effusion has greater density than the rest of the lung, it gravitates towards the lower portions of the

pleural cavity The pleural cavity, pleural space, or interpleural space is the potential space between the pleurae of the pleural sac that surrounds each lung. A small amount of serous pleural fluid is maintained in the pleural cavity to enable lubrication b ...

. The pleural effusion behaves according to basic fluid dynamics, conforming to the shape of pleural space, which is determined by the lung and chest wall. If the pleural space contains both air and fluid, then an air-fluid level that is horizontal will be present, instead of conforming to the lung space. Chest radiographs in the lateral decubitus position (with the patient lying on the side of the pleural effusion) are more sensitive and can detect as little as 50 mL of fluid. Between 250 and 600mL of fluid must be present before upright chest X-rays can detect a pleural effusion (e.g., blunted costophrenic angles). Chest computed tomography is more accurate for diagnosis and may be obtained to better characterize the presence, size, and characteristics of a pleural effusion. Lung

ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...

, nearly as accurate as CT and more accurate than chest X-ray, is increasingly being used at the point of care to diagnose pleural effusions, with the advantage that it is a safe, dynamic, and repeatable imaging modality. To increase diagnostic accuracy of detection of pleural effusion sonographically, markers such as boomerang and VIP signs can be utilized. File:Massive Effusion2008.jpg, Massive left-sided pleural effusion (whiteness) in a patient presenting with lung cancer. File:Pleura effusion.jpg, CT scan of the chest showing a left-sided pleural effusion. The fluid usually settles at the lowest space due to

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...

; in this case, at the back because the patient is supine. File:LungandEffusion.ogg, The lung expanding within an area of pleural effusion as seen by ultrasound File:Mesothelioma cytology 1.jpg,

Micrograph A micrograph or photomicrograph is a photograph or digital image taken through a microscope or similar device to show a magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken on a m ...

of a pleural fluid

cytopathology Cytopathology (from Greek , ''kytos'', "a hollow"; , ''pathos'', "fate, harm"; and , '' -logia'') is a branch of pathology that studies and diagnoses diseases on the cellular level. The discipline was founded by George Nicolas Papanicolaou in ...

specimen showing

malignant mesothelioma Mesothelioma is a type of cancer that develops from the thin layer of tissue that covers many of the internal organs (known as the mesothelium). The most common area affected is the lining of the lungs and chest wall. Less commonly the lining ...

, one cause of a pleural effusion. File:LargePleuralEffusionLatPlain.png, A pleural effusion as seen on lateral upright chest x-ray File:UOTW 23 - Ultrasound of the Week 1.webm, Pleural effusion as seen behind the heart. File:PMC2567296 1757-1626-1-225-2.png, Massive pleural effusion, later proven to be hemothorax in a South Indian male.

Thoracentesis

Once a pleural effusion is diagnosed, its cause must be determined. Pleural fluid is drawn out of the pleural space in a process called

thoracentesis Thoracentesis , also known as thoracocentesis (from Greek ''thōrax'' 'chest, thorax'—GEN ''thōrakos''—and ''kentēsis'' 'pricking, puncture'), pleural tap, needle thoracostomy, or needle decompression (often used term), is an invasive med ...

, and it should be done in almost all patients who have pleural fluid that is at least 10 mm in thickness on CT, ultrasonography, or lateral decubitus X-ray and that is new or of uncertain etiology. In general, the only patients who do not require thoracentesis are those who have heart failure with symmetric pleural effusions and no chest pain or fever; in these patients,

diuresis Diuresis () is increased urination (polyuria) or, in the related word senses more often intended, the physiological process that produces such an increase or the administration of medications to encourage that process. It involves extra urine pr ...

can be tried, and thoracentesis is avoided unless effusions persist for more than 3 days. In a thoracentesis, a needle is inserted through the back of the chest wall in the sixth, seventh, or eighth intercostal space on the midaxillary line, into the pleural space. The use of

ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...

to guide the procedure is now standard of care as it increases accuracy and decreases complications. After removal, the fluid may then be evaluated for: # Chemical composition including

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

,

lactate dehydrogenase Lactate dehydrogenase (LDH or LD) is an enzyme found in nearly all living cells. LDH catalyzes the conversion of lactate to pyruvate and back, as it converts NAD+ to NADH and back. A dehydrogenase is an enzyme that transfers a hydride from one ...

(LDH),

albumin Albumin is a family of globular proteins, the most common of which are the serum albumins. All the proteins of the albumin family are water-soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins ...

,

amylase An amylase () is an enzyme that catalyses the hydrolysis of starch (Latin ') into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. Foods that contain large amounts of ...

, pH, and

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...

#

Gram stain In microbiology and bacteriology, Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. The name comes from the Danish b ...

and culture to identify possible bacterial infections #

White White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White o ...

and

red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

counts and differential white blood cell counts #

Cytopathology Cytopathology (from Greek , ''kytos'', "a hollow"; , ''pathos'', "fate, harm"; and , '' -logia'') is a branch of pathology that studies and diagnoses diseases on the cellular level. The discipline was founded by George Nicolas Papanicolaou in ...

to identify cancer cells, but may also identify some infective organisms # Other tests as suggested by the clinical situation –

lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids includ ...

s,

fungal culture A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

,

viral culture Viral culture is a laboratory technique in which samples of a virus are placed to different cell lines which the virus being tested for its ability to infect. If the cells show changes, known as cytopathic effects, then the culture is positive. ...

, tuberculosis cultures, lupus cell prep, specific immunoglobulins

Light's criteria

Definitions of the terms "

transudate Transudate is extravascular fluid with low protein content and a low specific gravity (< 1.012). It has low nucleated cell counts (less than 500 to 1000 /microliter) and the primary cell types are 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. Transudative pleural effusions are defined as effusions that are caused by ''systemic'' factors that alter the pleural equilibrium, or

Starling forces The Starling equation describes the net flow of fluid across a semipermeable membrane. It is named after Ernest Starling. It describes the balance between capillary pressure, interstitial pressure, and osmotic pressure. The classic Starling equa ...

. The components of the Starling forces – hydrostatic pressure, permeability, and oncotic pressure (effective pressure due to the composition of the pleural fluid and blood) – are altered in many diseases, e.g.,

left ventricular failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, an ...

, kidney failure, liver failure, and

cirrhosis Cirrhosis, also known as liver cirrhosis or hepatic cirrhosis, and end-stage liver disease, is the impaired liver function caused by the formation of scar tissue known as fibrosis due to damage caused by liver disease. Damage causes tissue rep ...

. 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 Bacterial pneumonia is a type of pneumonia caused by bacterial infection. Types Gram-positive '' Streptococcus pneumoniae'' () is the most common bacterial cause of pneumonia in all age groups except newborn infants. ''Streptococcus pneumonia ...

,

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

,

pulmonary embolism Pulmonary embolism (PE) is a blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream ( embolism). Symptoms of a PE may include shortness of breath, chest pain particularly upon breathin ...

, and viral infection). 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. According to Light's criteria (Light, et al. 1972), a pleural effusion is likely exudative if at least one of the following exists: # The ratio of pleural fluid protein to serum protein is greater than 0.5 # The ratio of pleural fluid LDH and serum LDH is greater than 0.6 # Pleural fluid LDH is greater than 0.6 or times the normal upper limit for serum. Different laboratories have different values for the upper limit of serum LDH, but examples include 200 and 300 IU/l. 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. 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. 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 Albumin is a family of globular proteins, the most common of which are the serum albumins. All the proteins of the albumin family are water-soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins ...

levels in blood and pleural fluid are measured. If the difference between the albumin level in the blood and the pleural fluid is greater than 1.2 g/dL (12 g/L), this suggests that the patient has a transudative pleural effusion. However, pleural fluid testing is not perfect, and the final decision about whether a fluid is a transudate or an exudate is based not on chemical analysis of the fluid, but an accurate diagnosis of the disease that produces the fluid. The traditional definitions of transudate as a pleural effusion due to systemic factors and an exudate as a pleural effusion due to local factors have been used since 1940 or earlier (Light et al., 1972). Previous to Light's landmark study, which was based on work by Chandrasekhar, investigators unsuccessfully attempted to use other criteria, such as specific gravity, pH, and protein content of the fluid, to differentiate between transudates and exudates. Light's criteria are highly statistically sensitive for exudates (although not very statistically specific). More recent studies have examined other characteristics of pleural fluid that may help to determine whether the process producing the effusion is local (exudate) or systemic (transudate). The table above illustrates some of the results of these more recent studies. However, it should be borne in mind that Light's criteria are still the most widely used criteria. The Rational Clinical Examination Series review found that bilateral effusions, symmetric and asymmetric, are the most common distribution in heart failure (60% of effusions in heart failure will be bilateral). When there is asymmetry in heart failure-associated pleural effusions (either unilateral or one side larger than the other), the right side is usually more involved than the left. The instruments pictured are accurately shaped, however, most hospitals now use safer disposable

trocar A trocar (or trochar) is a medical or veterinary device that is made up of an awl (which may be a metal or plastic sharpened or non-bladed tip), a cannula (essentially a hollow tube), and a seal. Trocars are placed through the abdomen during lap ...

s. Because these are single use, they are always sharp and have a much smaller risk of cross patient contamination.

Treatment

Treatment depends on the underlying cause of the pleural effusion. Therapeutic aspiration may be sufficient; larger effusions may require insertion of an intercostal drain (either pigtail or surgical). When managing these chest tubes, it is important to make sure the chest tubes do not become occluded or clogged. A clogged chest tube in the setting of continued production of fluid will result in residual fluid left behind when the chest tube is removed. This fluid can lead to complications such as hypoxia due to

lung collapse A pneumothorax is an abnormal collection of air in the pleural space between the lung and the chest wall. Symptoms typically include sudden onset of sharp, one-sided chest pain and shortness of breath. In a minority of cases, a one-way valve ...

from the fluid, or

fibrothorax Fibrothorax is a medical condition characterised by severe scarring (fibrosis) and fusion of the layers of the pleural space surrounding the lungs resulting in decreased movement of the lung and ribcage. The main symptom of fibrothorax is shortn ...

if scarring occurs. Repeated effusions may require chemical (

talc Talc, or talcum, is a clay mineral, composed of hydrated magnesium silicate with the chemical formula Mg3Si4O10(OH)2. Talc in powdered form, often combined with corn starch, is used as baby powder. This mineral is used as a thickening agent a ...

,

bleomycin -13- (1''H''-imidazol-5-yl)methyl9-hydroxy-5- 1''R'')-1-hydroxyethyl8,10-dimethyl-4,7,12,15-tetraoxo-3,6,11,14-tetraazapentadec-1-yl}-2,4'-bi-1,3-thiazol-4-yl)carbonyl]amino}propyl)(dimethyl)sulfonium , chemical_formula = , C=55 , H=84 , N=1 ...

,

tetracycline Tetracycline, sold under various brand names, is an oral antibiotic in the tetracyclines family of medications, used to treat a number of infections, including acne, cholera, brucellosis, plague, malaria, and syphilis. Common side effects in ...

/ doxycycline), or surgical

pleurodesis Pleurodesis is a medical procedure in which part of the pleural space is artificially obliterated. It involves the adhesion of the visceral and the costal pleura. The mediastinal pleura is spared. Uses Pleurodesis is performed to prevent recurre ...

, in which the two pleural surfaces are scarred to each other so that no fluid can accumulate between them. This is a surgical procedure that involves inserting a chest tube, then either mechanically abrading the pleura or inserting the chemicals to induce a scar. This requires the chest tube to stay in until the fluid drainage stops. This can take days to weeks and can require prolonged hospitalizations. If the chest tube becomes clogged, fluid will be left behind and the

pleurodesis Pleurodesis is a medical procedure in which part of the pleural space is artificially obliterated. It involves the adhesion of the visceral and the costal pleura. The mediastinal pleura is spared. Uses Pleurodesis is performed to prevent recurre ...

will fail. Pleurodesis fails in as many as 30% of cases. An alternative is to place a PleurX Pleural Catheter or Aspira Drainage Catheter. This is a 15Fr chest tube with a one-way valve. Each day the patient or caregivers connect it to a simple vacuum tube and remove from 600 to 1000 mL of fluid, and can be repeated daily. When not in use, the tube is capped. This allows patients to be outside the hospital. For patients with

malignant pleural effusion Malignant pleural effusion is a condition in which cancer causes an abnormal amount of fluid to collect between the thin layers of tissue (pleura) lining the outside of the lung and the wall of the chest cavity. Lung cancer and breast cancer accoun ...

s, it allows them to continue chemotherapy if indicated. Generally, the tube is in for about 30 days, and then it is removed when space undergoes spontaneous pleurodesis. Tubercular pleural effusion is one of the common extrapulmonary forms of tuberculosis. Treatment consists of antituberculosis treatment (ATT). The currently recommended ATT regime is two months of isoniazid, rifampicin, ethambutol and pyrazinamide followed by four months of isoniazid, rifampicin and ethambutol.

References

External links

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Pleural Effusion
Images from MedPix {{DEFAULTSORT:Pleural Effusion Disorders of fascia Diseases of pleura Articles containing video clips

Types

Causes

Transudative

Exudative

Other/ungrouped

Pathophysiology

Diagnosis

Imaging

Thoracentesis

Light's criteria

Treatment

See also

References

External links