Effusion Definition, Types, Causes, Symptoms, Treatment

Effusion Definition

Effusion is the term for accumulation of fluid in a body cavity particularly within the cranial cavity, in the middle ear, around the lungs, around the heart, in the abdomen (peritoneal cavity) and in the joint spaces. It is also referred to as fluid retention or water retention because most of the fluid is composed of water. However, sometimes blood or pus can be mixed with the fluid and collect in these cavities.

Difference between Effusion and Edema

Fluid retention can also refer to edema which is commonly known as tissue swelling. Edema is the accumulation of excess fluid within the tissues whereas the term effusion indicates collection of fluid within a cavity of the body. There is sometimes confusion about these terms, particularly with certain organs like the lung. For example if there is fluid in the lung then it is known as pulmonary edema but fluid around the lung is known as a pleural effusion.

Effusion Meaning

What is an effusion?

An effusion is an abnormal collection of fluid within a cavity. Sometimes there is a little fluid within some of these cavities that is considered to be normal and is mainly for lubrication or proection. It is more likely to be present within double layered sacs like the pericardium (heart), pleura (lungs) and peritoneum (abdomen). These fluid in these instances is only about 10mL to 20mL depending on the site. The fluid in the cranial cavity, around the brain, known as the cerebrospinal fluid is present in much larger amounts normally since its function is to absorb shock and protect the brain.

The excess fluid that collects in these cavities can be one of two types – transudates or exudates. Normally the linings of these cavities secrete fluid for its specific purpose in carefully controlled quantities. Any change in local conditions, however, will allow for the accumulation of transudative or exudative fluid.

Transudates occur with a disturbance between the hydrostatic pressure or colloid osmotic pressure allowing fluid from the blood vessels to seep out or fluid from the tissue spaces to be pushed out into a cavity. It is not associated with inflammation. Exudates on the other hand arise more commonly with inflammatory conditions. In the inflammation process, the blood flow to the inflamed area increases and the blood vessels become more porous allowing large amounts of fluid from the blood, along with certain blood proteins, to exit the blood vessels and pass into the cavities. Sometimes the tiny blood vessels (microvasculature) is damaged and the vessels are partially ruptured thereby allowing for the free flow of whole blood.

Effusion Causes

The causes of an effusion differ depending on the site. Effusions are either transudates or exudates and may have varying quantities of pus or blood in some cases. One of the main factors is inflammation of the lining of the respective cavities. These linings usually produce varying degrees of fluid for lubrication and/or protection. When irritated, the fluid secretion from these linings increases significantly often exceeding the drainage ability. Fluid then accumulates in the cavity.

Infections at the site, other inflammatory diseases, trauma, radiation therapy,chemotherapy, certain medication, congestive heart failure, kidney failure and liver disease are some of the common causes among the various sites. However, specific causes of an effusion for individual sites may differ.

Effusion Symptoms

An effusion in almost any cavity is largely asymptomatic until the fluid accumulation reaches a state where it causes distention of the affected area, pain or compression of the internal structures.


Swelling of the affected site is the main symptom. However, this may not always be visibly evident if the outer wall is rigid like within the cranial or thoracic cavities.


Pain may occur with stretching of the outer coverings or compression of tissue. This can vary in intensity from a sensation of fullness and discomfort to dull or excruciating pain. It is usually in line with the degree of fluid accumulation.

Loss of Function

The compression of internal structures may not only cause pain, but also reduce blood supply to the area and even lead to tissue death. This in turn has a wide variety of effects depending on the affected site but is mainly seen as dysfunction of the affected organs. For example, when the lungs are affected there is difficulty breathing.

Effusion Treatment

The treatment is directed at the cause of the effusion. This may be a combination of medication and drainage depending on the severity of the fluid accumulation. Other types of surgery may also be indicated depending on the site, cause and degree of tissue damage.

Types of Effusion

Although an effusion is mainly exudative or transudative, it may be further classified by its composition which is also largely dependent on the cause of effusion.

  • Serous effusion is similar to tissue fluid and the fluid of the blood (serum) with very little proteins.
  • Fibrinous effusion is where there is a large number of proteins, particularly fibrin and fibrinogen. These components are important for blood clotting but when present in the tissue spaces or body cavities it may cause the formation of scar tissue.
  • Puruluent effusion (suppurative effusion) is the presence of pus within the accumulated fluid. At times, most of the fluid can be pus although it is more often mixed with exudative or transudative fluid.
  • Hemorrhagic effusion is the presence of whole blood within the accumulated fluid. As with pus, sometimes blood itself can occupy the pleural space rather than being mixed with the existing effusion.

Effusion of the Lung

The lung is contained within a double layered sac known as the pleura. One layer, the visceral pleura, adheres to the lung itself while the other layer, parietal pleura, is attached to the inner chest wall. Between these two layers is a potential space  known as the pleural cavity. Here there is about 1mL to 5mL of a serous fluid that serves as a lubricant which is known as pleural fluid.

Pleural Effusion Definition

A pleural effusion is when there is an abnormal accumulation of fluid within the pleural cavity. However, it is commonly referred to as water on the lungs or fluid around the lungs. It must not be confused with pulmonary edema which is fluid in the lungs. When there is an accumulation of blood within the pleural space it is referred to as hemothorax and if lymphatic fluid then it is known as a chylothorax.

Pleural Effusion Causes

There are a large number of causes of a pleural effusion. The cause determines the type of fluid that is present in the pleural space. Some of the causes includes :

  • Pneumonia
  • Pleurisy (pleuritis)
  • Chest trauma
  • Following open heart surgery
  • Cancer of the lung or pleura
  • Pulmonary embolism
  • Pulmonary tuberculosis
  • Asbestosis
  • Sarcoidosis
  • Heart failure
  • Kidney disease
  • Liver cirrhosis
  • Ovarian disease

Pleural Effusion Symptoms

As with most effusions, a significant amount of fluid needs to accumulate in the pleural cavity before symptoms of the effusion becomes evident. These symptoms may include :

  • Chest pain
  • Difficulty breathing (dyspnea)
  • Shortness of breath when lying flat (orthopnea)
  • Dry cough
  • Hiccups
  • Rapid breathing (tachypnea)

Pleural Effusion Treatment

Treatment depends on the underlying cause and the effusion itself may resolve if the condition is successfully treated. Therefore no specific therapeutic measures are needed in these instances. Medication such as diuretics may help rid the body of excess fluid in conditions such as congestive heart failure. Therapeutic thoracentesis, commonly known as a pleural tap, is a procedure for draining pleural fluid.

Sometimes when there is recurring pleural effusions, certain sclerosing agents are introduced into the pleural space to cause fibrosis of the pleura (pleural sclerosis). More invasive procedures include video-assisted thoracoscopic surgery (VATS) or open thoracic surgery (thoracotomy) for removal of fibrous tissue in infections or causing fibrosis is recurrent effusions or with malignancies (pleural sclerosis).

Effusion of the Heart

The heart is covered by a double layered sac known as the pericardium. The visceral pericardium adheres to the outer surface of the heart (epicardium) while the parietal pericardium is attached to the fibrous pericardium which attaches to the chest wall. The space between the visceral and parietal pericardium is known as the pericardial space or cavity. A small amount of fluid is normally present in this spaces and is known as pericardial fluid. Its main purpose is for lubrication.

Pericardial Effusion Definition

A pericardial effusion is the abnormal accumulation of fluid in the pleural space around the heart. It is commonly known as fluid around the heart. If there is an excessive collection of fluid, it may compress the heart and this is known as a cardiac tamponade. It is potentially life threatening in these cases.

Pericardial Effusion Causes

Inflammation of the pericardium (pericarditis) is one of the main reasons for a pericardial effusion. Some of the causes of pericardial effusion, which may or may not be associated with pericarditis, includes :

  • Infections – viral, bacterial, tuberculous
  • Following open heart surgery (Dressler syndrome)
  • Trauma to the chest wall and heart
  • Cancer – primary (heart or pericardium) or secondary (metastatic spread from distant sites)
  • Endocrine disorders like hypothyroidism
  • Inflammatory diseases, particularly autoimmune disorders such as systemic lupus erythematosus (SLE)
  • Kidney failure with uremia
  • Iatrogenic – radiation therapy, chemotherapy and certain medication

Pericardial Effusion Symptoms

  • Difficulty breathing (dyspnea) which may also be associated with painful breathing
  • Shortness of breath when lying flat pain (orthopnea)
  • Retrosternal chest pain (behind breastbone)
  • Dry cough
  • Dizziness
  • Rapid heart rate
  • Low-grade fever (sometimes)

Pericardial Effusion Treatment

Treatment options for a pericardial effusion will depend on the cause. The quantity of accumulated fluid and the risk of a cardiac tamponade will also be taken into consideration. Medication may include NSAIDs to reduce the inflammation, antibiotics to treat bacterial infections and diuretics to increase water excretion in congestive heart failure. A pericardiocentensis is the procedure for draining pericardial fluid. Other procedures are more invasive and may include open heart surgery to remove damaged tissue, drain excessive fluid and seal any sites of bleeding. Pericardial sclerosis is where a sclerosing agent is introduced into the pleural space to cause fibrosis and bond the two pericardial layers if there is a recurring effusion. Sometimes a portion of the pericardium may have to be removed in instances of cancer or other causes of recurrent effusions.

Effusion of the Brain

The brain essentially floats in a watery medium known as the cerebrospinal fluid (CSF) within the intracranial cavity. The CSF serves as a shock absorber ensuring that the brain does not strike against the skull when subjected to sudden or intense force. There is about 150mL of cerebrospinal fluid in the intracranial cavity at any one time although some 500mL to 700mL is produced in a day.

A constant balance in the volume is maintained by production and drainage. Most of this fluid is produced by the choroid plexus in the brain, drains out into the ventricles through formaina and into the subarachnoid space that surrounds the brain. From here it flows into the arachnoid villa and then into several venous sinuses which drain into the venous circulation.

Fluid on the Brain Causes

There are several disorders where there is an increase in intracranial pressure due to fluid accumulation. It is commonly referred to as water on the brain or fluid retention in the skull. The two most notable conditions is hydrocephalus and subdural effusion.

  • Hydrocephalus is an excessive accumulation of cerebrospinal fluid (CSF) within the intracranial cavity due to increased production or decreased drainage.
  • Subdural effusion is a rare condition where fluid accumulates in the subdural space. If pus collects at the site then it is known as subdural empyema. It tends to arise as a complication of meningitis.

Fluid on the Brain Symptoms

  • Headache
  • Papilledema – swelling of the optic disc of the eye
  • Vomiting
  • Confusion and other mental disturbances
  • Seizures
  • Dizziness
  • Fainting
  • Neurological abnormalities

Fluid on the Brain Treatment

Treating the underlying cause may halt the buildup of additional fluid and possibly even resolve spontaneously. Medication may be used to decrease CSF secretion or increase CSF resorption  in hydrocephalus or antibiotics to treat the infection in meningitis. Surgery is indicated for drainage of fluid and removal of damaged tissue. A cerebral shunt helps with the drainage of the excess fluid.

Effusion of the Joints

The joint is the meeting of two bones in a manner that allows for movement. Each surface of the bone involved in the joint is surrounded by articular cartilage. There is small space between the two opposing surfaces known as the joint space or intra-articular space. The thin synovial membrane (synovium) covers the joint and also secrete synovial fluid into the joint space. This fluid serves as a shock absorber and also as lubricant for the smooth movement of the bones within the joint space.

Joint Effusion Definition

A joint effusion is the excessive accumulation of fluid within the joint space. In most cases this is due to the collection of synovial fluid but sometimes there may be pus or blood within the joint space. The excess fluid hampers the normal joint movement due to the increased intra-articular pressure as a result of joint swelling. The knee is most commonly affected.

Joint Effusion Causes

The most common causes of a joint effusion are related to arthritis, particularly rheumatoid, psoriatic and septic arthritis. Osteoarthritis does not normally present with an effusion. Therefore, some of the causes of a joint effusion includes :

  • Trauma
  • Joint infection, particularly bacterial
  • Systemic infections
  • Autoimmune diseases
  • Gout

Joint Effusion Symptoms

Accumulation of fluid within the joint may be asymptomatic until the fluid collection becomes excessive. When symptomatic, a joint effusion may present as :

  • Joint swelling
  • Discomfort or pain in the joint
  • Stiffness
  • Redness and warmth of the overlying skin are more likely to be associated with inflammatory causes.
  • Joint deformity and nodules may be a consequence of the underlying disease that also causes an effusion.

Joint Effusion Treatment

The treatment for a joint effusion depends on the cause but usually commences with medication. NSAIDs (non-steroidal anti-inflammatory drugs) is the drug of choice as it also helps with managing the pain. Corticosteroids may be be used in more severe and persistent cases and can be injected into the joint space (intra-articular injections). In conditions such as rheumatoid and psoriatic arthritis, drugs that suppress the immune system may be used to control the immune-mediated inflammatory reaction. Drugs such as xanthine oxidase inhibitors, probenicid or colchicine may be used to treat the disorder in uric acid metabolism as is seen in gout. Arthrocentesis (joint aspiration) is the procedure for draining excess fluid from the joint space but is only a viable option for larger joints like the knee.

Effusion in the Middle Ear

The middle ear is the space that lies beyond the tympanic membrane and further separated from the inner ear by the round and oval window. It is a somewhat box-shaped area with the eustachian tube running down to the nasopharynx. Most mucus within the middle ear can drain out through this tube into the back of the throat and air is able to enter and equalize the pressure with that of the outer ear. Normally there is very little fluid in the middle ear, serving only to moisturize the tissue lining its walls.

Middle Ear Effusion Definition

A middle ear effusion is the accumulation of fluid within the middle ear and is commonly referred to as fluid behind the eardrum. The fluid is almost always mucoid (mucus) or serous. It usually accompanies otitis media and is more correctly known as otitis media with middle ear effusion. However, not every case of otitis media will be associated with an effusion. It is also commonly known as secretory otitis media or ‘glue ear’.

Middle Ear Effusion Causes

Middle ear effusion is associated with otitis media – inflammation of the middle ear. This causes the middle ear lining to secrete a mucoid or serous fluid. Normally this fluid would drain out through the eustachian tube but there is almost always some dysfunction of the tube. The fluid remains trapped within the middle ear and gradually accumulate. It is more common in children. The main causative factor for otitis media is an infection, either bacterial or viral in nature. However, it is the eustachian tube dysfunction that causes the build up of the fluid (effusion). Another form of otitis media known as chronic suppurative otitis media may give rise to a purulent discharge (pus) but typically leads to a perforation of the ear drum thereby allowing the pus to drain out through the ear canal.

Middle Ear Effusion Symptoms

Symptoms of a middle effusion can vary depending on the severity. It is the most common cause of conductive hearing loss in children. Other symptoms may include :

  • Earache, ear pain
  • Poor balance
  • Headache
  • Fever
  • Ear discharge
  • Sore throat
  • Popping sound or fluid sound in the ear
  • Changes in shape (like bulging) or color (yellow to red) of the eardrum

Children may present with other symptoms such as difficulty sleeping, constantly tugging on the ear, irritability, vomiting and diarrhea.

Middle Ear Effusion Treatment

Medication is the main therapeutic approach initially. Antibiotics are prescribed for bacterial infections and corticosteroids to reduce inflammation. Pain relieving oral drugs and ear drops may help with relieving the pain. Surgical intervention may involve a myringotomy where a small opening is created  in the ear drum and the fluid is then drained. Pressure equalization tubes (PET), also known as ear grommets, may be inserted into the drum to allow for continuing drainage. Surgical removal of the adenoids (adenoidectomy) may also be useful and can help to restore eustachian tube function.

Effusion in the Abdomen

Most of the abdominal organs are contained within a membranous sac known as the peritoneum. One layer, the visceral peritoneum, adheres to the abdominal organs while the other layer, the parietal peritoneum, is attached to the inner abdominal wall. A very small amount of fluid, the peritoneal fluid, exists in the space between these two layers (peritoneal space or cavity). In fact men may have little or no fluid while women may find slight changes in the fluid levels during the menstrual cycle. The quantity of fluid almost never exceeds 20mL.

Peritoneal Effusion Definition

Ascites is the term for an abnormal collection of fluid within the peritoneal cavity. It may or may not be associated with inflammation of the peritoneum – peritonitis. Ascites is commonly referred to as fluid retention in the abdomen but most cases of abdominal distention, particularly in instances like intermenstrual bloating, is not due to fluid accumulation. More than 1,000mL of fluid needs to accumulate in the peritoneal cavity before distention becomes evident.

Peritoneal Effusion Causes

Majority of ascites cases is due to liver disease (hepatic causes) such as :

  • Cirrhosis
  • Alcoholic hepatitis
  • Non-alcoholic steatohepatitis
  • Liver cancer
  • Biliary disease

The more common non-hepatic causes includes peritonitis, pancreatitis and congestive heart failure. Other non-hepatic causes of ascites are less commonly seen.

Peritoneal Effusion Symptoms

The signs and symptoms of ascites depends on the amount of fluid that is within the peritoneal cavity. There is usually no symptoms if the fluid collection is less than 500mL. Ascites is graded to determine the severity based on the symptoms that are present – grade 1 has little or very mild symptoms, grade 2 is moderate ascites with some of the symptoms and grade 3 is for massive ascites with severe symptoms.

  • Abdominal distention
  • Bloated – sensation of fullness
  • Abdominal discomfort but usually no pain
  • Difficulty breathing
  • Weight gain
  • Flattened or everted umbilicus
  • Nausea
  • Lack of appetite

Peritoneal Effusion Treatment

As with an effusion anywhere in the body, the treatment is directed at the underlying cause. Some of the therapeutic measures may include a sodium restricted diet, medication like diuretics to increase fluid excretion and therapeutic paracentesis to drain the fluid from the abdomen.

Please note that any information or feedback on this website is not intended to replace a consultation with a health care professional and will not constitute a medical diagnosis. By using this website and the comment service you agree to abide by the comment terms and conditions as outlined on this page