Exudate: History, Composition, Volume, Evaluation, Types and Management

It is closely related to the body and its natural healing mechanism. I’ve probably observed it first-hand.

Where exactly? Think of the little square of white cotton on the back of a band-aid.

The drainage collected in this piece of cotton is exuded. Now, back off and explain how this exudate came to your bandage.

Your skin is an excellent barrier against infections. But accidents happen, and, sometimes, the skin barrier is broken, either by a cut or scratch or by some other type of injury. After an injury, the body’s repair mechanisms come into play.

The “soldered” cells, a specific type of white blood cell, are sent to the area to fight against any infection that may try to enter through the open tissue.

Some of these “soldier” cells die, as do some skin cells damaged in the injury. All these dead cells contribute to forming something called an exudate.

Exudate is a fluid rich in proteins and cellular elements emitted by an organism through pores or a wound, a process known as exudate, which oozes blood vessels due to inflammation and deposits in nearby tissues.


The altered permeability of blood vessels allows the passage of large molecules and solid matter through their walls. The glasses seem to cry, to sweat, by the Latin “exudates,” to sweat, from which the exudate is derived.

The exudate is derived from exuding, “spilling,” from the Latin exsūdāre, “exuding as sweat” (ex “going out” and sweating “sweating”).

A transudate is a fluid that passes through a membrane that filters a large part of the protein and cellular elements and produces an aqueous solution. It is a normal part of the healing process. However, sometimes the infection is established, changing the appearance of the exudate.

The transudation process is due to an increase in pressure in the veins and capillaries by pressing the fluid through the vessel’s walls or low protein levels in the serum. The transudate is a blood filter.

History and composition

The Swiss physician Paracelsus described the exudate of the wound (c1491-1541) as a balm of nature. It is derived from the serum through the inflammatory process/extravasation.

The acute exudate of the wound contains molecules and cells that are vital to support the healing process. It has a high protein content (although lower than that found in the serum), with a specific gravity greater than 1.020.

Its composition includes electrolytes, glucose, cytokines, leukocytes, metalloproteinases, macrophages, and microorganisms. Platelets and fibrin may be present in the first 48 to 72 hours after the injury, but this is reduced as bleeding decreases.

As the fluid passes through the inflamed walls of the vessel (extravasation), it can be seen that the wound exudate is essentially modified whey and, therefore, will contain similar solutes.

This fluid may be contaminated with tissue and microorganism debris as it reaches the wound’s surface. Acute healing wounds produce exudate that contains active growth factors. These are not present in chronic wounds.

Exudate in medicine

Also known as drainage, exudate is a fluid produced by the body in response to tissue damage.

“We want our patients’ wounds to be moist but not excessively wet. The type of drain can tell us what is happening in an injury. “

An exudate is any fluid that leaks from the circulatory system to injury or areas of inflammation. It can be a fluid similar to pus or transparent.

When an injury occurs, leaving the skin exposed, it escapes from the blood vessels and nearby tissues. The fluid is composed of serum, fibrin, and white blood cells. The exudate may ooze from cuts or areas of infection or inflammation.


The treatment of wound exudate requires the clinician to understand what it is, why it is present and how to control and evaluate it accurately.

The production of wound exudate occurs due to vasodilation during the early inflammatory stage of healing under the influence of inflammatory mediators such as histamine and bradykinin.

It presents as serous fluid in the wound bed and is part of the routine healing of wounds in acute wounds.

However, when the wound becomes “chronic” and does not heal with persistent and abnormal inflammation or when the infection is established, the exudate acquires a different appearance and generates clinical challenges.

The exudate contains proteolytic enzymes and other components not seen in acute injuries in chronic wounds. This type of exudate has justifiably been described as a “wound agent in itself” because it can degrade growth factors and perilesional skin and predisposes to inflammation.

To develop a practical management approach, the clinician must accurately assess and understand the implications of the composition and the amount of exudate present in the wound.

The exudate must be effectively managed if the optimum moist environment necessary for the healing of the wound is created and the surrounding skin is protected from the risks of maceration.

To achieve these objectives, detailed knowledge of the materials of the dressings and their performance is required. It is also necessary to understand the impact of other treatments and comorbidities on exudate production.

Exudate management is relevant to the patient’s quality of life problems, as it is often associated with leaks and foul odors. It impacts the health economy because the lack of control of exudate production will increase management costs and patient morbidity.

This review considers the exudate from the perspective of its nature, composition, evaluation, and the range of available management strategies.

Pleural exudates:

Exudative effusions result from the chemotactic (causing the accumulation of white blood cells) and vasoactive substances (which cause high protein outflow) within the pleural cavity secondary to an inflammatory process.

Degenerate neutrophils will usually predominate with a bacterial infection.

Bacteria can originate from hematogenous or lymphatic dissemination, penetrating agents (iatrogenic, inhaled or external foreign bodies, bite wounds, trauma), or spread of infected organs (pulmonary, gastrointestinal).

Aerobic and anaerobic cultures are recommended for all exudates.

Other organisms, such as fungi, protozoa, and rickettsiae, can also cause septic pleural exudates.

In aseptic exudates, the predominant cell type can include non-degenerate neutrophils (inflammation), small lymphocytes (chylothorax), or neoplastic cells.

Potential causes of an aseptic exudate include pneumonia and other well-circumscribed infections (e.g., abscess), generalized sepsispancreatitis, or necrosis of intracavitary neoplasia.

Exudative optic neuropathy:

It appears as a white to gray material that obscures the optic nerve, which, if visible, is edematous with or without hemorrhages.

The cause is unknown, but it is believed to be an ocular response to various systemic diseases such as infection by Streptococcus equi or Actinobacillus equal and septicemia.

This should be distinguished from benign exudative/proliferative optic neuropathy, a condition of white or gray material anterior to the optic nerve in a visual eye with otherwise normal findings on examination.

On histological examination, the lesion resembles a schwannoma. Neoplasia of the optic nerve, traumatic optic neuropathy, and ischemic optic neuropathy are also differential diagnoses.

Peritoneal exudate fluid:

It is tiny in quantity and contains some neutrophil leukocytes, macrophages, and lymphocytes. Therefore, the peritoneal exudate is usually collected to obtain leukocytes, especially free macrophages.

Peritoneal exudate cells resident in intact mice and the most significant number of stimulated cells are harvested and used for experimental purposes. This section describes the general procedure for the collection of stimulated peritoneal exudate.

Stimulants are used, including 5% glycogen, 2.4% fluid of a thioglycollate medium, and 10% protease peptone.

Family exudative vitreoretinopathy (FEVR):

It is usually autosomal dominant (chromosome 11) but occasionally recessive, linked to X, and sporadic. It produces a background appearance similar to retinopathy of prematurity.

Three stages are based on the severity of the retinal characteristics:

  • Peripherally not perfusion, especially temporarily.
  • Localized tractional retina detachment, exudation, and neovascularization.
  • More extensive tractional, exudative, and regenerative details.

Fluorescein angiography shows areas of non-perfusion and filtration. Most cases are mild but often progressive, so observation is required.

Some require retinal photocoagulation to reduce ischemic stimulation or retinal detachment surgery.

The volume of exudate:

In chronic wounds, the inflammatory response is altered due to an uncontrolled expression of inflammatory mediators with a simultaneous increase in vascular permeability and the amount of extravascular fluid.

If the wound becomes infected, an abrupt increase in the volume of the exudate can be observed, followed by other quantitative and qualitative changes. This has been attributed in part to specific mechanisms of bacterial virulence that produce vasodilation and extravasation.

Gautam et al. (2001) have described a process whereby neutrophils attracted to the lesion site trigger the release of heparin-binding protein (HBP).

It has also been shown that chronic exudate of the leg ulcer contains increased levels of heparin-binding protein compared to acute wound fluid. The heparin-binding protein is likely involved in the production of increased exudate.

Certain bacteria, such as Pseudomonas aeruginosa, stimulate the release of heparin-binding protein from neutrophils, which aggravates chronic inflammation by increasing endothelial hyperpermeability.

Recent research has indicated that some bacteria express histamine and, therefore, if present, produce an additional physiological source of histamine in the wound environment. Morganella species, M. morganii, and Gram-negative bars have been found to express histamine.

It has been found that bacteria isolated from chronic wounds produce physiologically significant histamine levels. It has not yet been determined whether the production of this proinflammatory agent can be controlled effectively by applying antihistamines.

Exudate evaluation:

An accurate evaluation of the volume and viscosity of the exudate will indicate whether the healing is progressing normally or not.

Inspection of a dressing during extraction can provide valuable information about the level of exudate produced during the time of use of the sauce.

To evaluate the volume of exudate, the health professional should count the number of dressings used over some time, observe the time of use of individual bandages, examine the application to detect the presence of strikethrough (wet or dry), examine the state of the perilesional skin and notice any leak.

Part of the subjectivity associated with the evaluation of exudate can be reduced using a tool such as an exudate continuum. This is an integral part of the applied wound management approach described by Gray et al.

This tool can assist in accurately assessing exudate and provide support in the decision-making process. It offers a method to generate a score relevant to volume and viscosity.

For example, suppose a score of 4 is obtained using the continuous exudate (medium volume 3 and low viscosity 1) and increases to 8 (high volume 5 and average viscosity 3) for three days. In that case, the wound will likely deteriorate, and It may be infected.

If the chosen intervention is adequate, such as an absorbent antimicrobial bandage, this is likely to be reflected in a lower score after a few days.


Exudate is an excellent indicator of how a wound is healing. The color, thickness, and odor of the exudate are all clues as to whether a patient’s wound is healing well or if there is a problem. The most common forms of exudate are:

Purulent or suppurative exudate consists of plasma with active and dead neutrophils, fibrinogen, and necrotic parenchymal cells.

The severe drainage/exudate is clear, thin, and watery plasma. It is expected during the inflammatory phase of wound healing, and it is considered that a smaller amount is deemed to be normal drainage of the wound.

This is the most common form of exudate seen emitted from a wound. It is a sign of routine wound healing. As the skin comes back together, there are natural wastes, such as dead cells and proteins.

The waste is removed through this clear oozing fluid called a serous exudate. The serous exudate usually has no odor.

However, a moderate to solid amount may indicate a high biological load.

This type of exudate is consistent with more severe infections and is commonly referred to as pus. It is thick and opaque. It can be tan, yellow, green or brown. It is never expected in a wound bed.

An easy way to remember about serous exudate is with “serious is NOT serious.” This will remind you that this type of drainage from a wound is considered normal during the healing process.

The fibrinous exudate is composed mainly of fibrinogen and fibrin. It is characteristic of rheumatic carditis but is seen in all severe injuries, such as strep throat and bacterial pneumonia.

Fibrinous inflammation is often difficult to resolve because the blood vessels grow into the exudate and fill the space occupied by the fibrin. Usually, large amounts of antibiotics are needed for resolution.

The catarrhal exudate is observed in the nose and throat and is characterized by a high mucus content.

Serous exudate (sometimes serous transudate) is usually seen in mild inflammation with relatively low protein. Its consistency resembles serum and can generally be seen in certain disease states such as tuberculosis.

Malignant (or cancerous) pleural effusion is an effusion where there are cancer cells. Usually, it is classified as exudate.

The seropurulent exudate is thin, watery, cloudy, and yellow to tan.

The bloody exudate is recent bleeding, seen in deep partial-thickness and full-thickness wounds. A small amount may be expected during the inflammatory stage, but we do not want to see blood in the wound exudate, which may indicate trauma to the wound bed.

Serosanguineous exudate is thin, watery, and pale red to pink. It seems everyone’s favorite type of drainage to document, but unfortunately, it is not what we want to see in a wound. The pink tint, which comes from red blood cells, indicates damage to the capillaries with changes in the dressing.

Methods used to manage the exudate.

Dressings :

If bandages are indicated, careful selection and careful determination of the time of use are imperative. This will help maintain an optimum moist environment while protecting the surrounding skin from maceration.

Specific key performance characteristics are required for such a dressing: they must absorb and retain the exudate, maintain the chronic harmful exudate from the wound away from the surrounding skin, function efficiently when used under compression, and be easy to remove demonstrate that it is cost-effective.

Wound dressings exhibit various fluid handling mechanisms: absorption, gelation, retention, and moisture vapor transmission. Information on the fluid management mechanism of a bandage is available from manufacturers.

This information is not always based on accepted and independent test methodologies but internal laboratory data favorable for the manufacturers’ products.

There are standard test methods published as monographs in various pharmacopeias and in peer-reviewed journals that provide independent and objective data on the treatment of the dressing fluid.

The basic mechanisms of bandaging are the following:


The exudate is absorbed in the bandage matrix. In the case of some foam dressings, this is a reversible mechanism; the fluid can be expressed from the pressure bandage. Not all foams behave this way.


After absorption, the exudate interacts with the bandage material to form a gel. This is a typical attribute of alginates: these carbohydrate polymers gel according to their composition’s proportion of uronic acid units.

However, with alginate gels, the fluid may contact the perilesional skin. This can also occur with hydrocolloid gel; the degree of the polymer composition depends.

Fluid retention:

In dressings with this mechanism, the dressing absorbs the fluid and is no longer available to wet the surrounding skin. Said materials retain the absorbed fluid directly on the wound, without lateral dissemination or “lateral wicking.”

An example of this is the Hydrofiber technology. It has been shown that these dressings are clinically effective and profitable in managing exudate, even when used under compression.

Transmission of moisture vapor:

In recent years, the dressings were designed to absorb fluid and, through an intermediate “wick” layer, move the fluid away from the wound/skin interface towards a porous backing layer.

Here, part of the fluid is lost in the atmosphere by evaporation, known as moisture vapor transmission. This mechanism is intended to increase the fluid handling capacity of the dressing. The success of this process depends on the proportion of liquid absorbed that is lost.

Evaporation will be compromised by occlusion materials, such as compression bandages, which can reduce evaporation rates.

There are no clinical data to suggest that this works in practice. Some doctors are skeptical that it has any value in improving performance.

Antimicrobial properties:

Dressings with an antimicrobial component are intended to control the biological burden of the wound in critical colonization and local infection.

These dressings are helpful; therefore, when high exudate levels are attributed to bacterial causes, there is also justification for its use in cases of disseminated infection where systemic antibiotics have been used, and altered perfusion is suspected.

Typical antimicrobial dressings are those that contain silver, iodine, or honey.


Topical negative pressure therapy:

Suction drainage from wounds has been used for many years, and there are a variety of systems.

It is claimed that the integrated technique of vacuum-assisted closure improves perfusion, reduces edema, and promotes the formation of granulation tissue and is supported by evidence of many types of wounds, including trauma injuries, pressure ulcers, ulcers in the legs, and surgical wounds.

Exudate removal, particularly the more vicious forms, also eliminates bacteria and protease enzymes, both barriers to healing. However, this technique should not be used on wounds that contain eschar or necrotic tissue.


In the healthy limb, the return of venous blood to the heart is achieved through the combined actions of the calf muscle pump and the foot pump, which require reasonable mobility and dorsiflexion of the ankle.

Where venous ulceration occurs, the patient needs help to achieve the return of venous blood. Compressive bandaging and intermittent pneumatic compression therapy have been found effective.

While compression is recognized as the cornerstone of the treatment of venous disease, there are recognized limitations to current bandage systems; for example, the applied pressure is unknown, depends on the method of application, and is highly variable.

Compression therapy has two main functions: counteract venous hypertension and control edema. To achieve these functions, the exudate is reduced in the venous ulcer of the uninfected leg.

In lymphedema, the application of appropriate bandages or compression garments will reduce both edema of the limb and any leakage of exudate.

The intermittent pneumatic compression therapy is administered through a boot-shaped device that, using a pump, is inflated and deflated to achieve an alternate and dynamic compression of the encapsulated limb.

Intermittent pneumatic compression can be used as the primary compression method or complement the orthodox compression bandage.

Elevation / exercise:

In venous ulceration of the leg, the patient is advised to elevate the affected limb (with the ankle above the heart level) to achieve venous blood return.

While this is not always practical, a certain degree of elevation will help the venous return and, as a result, will reduce exudate. Manual drainage and exercise are essential to control edema and leakage in lymphedema.

Exudates vs. Translated

The transudates and exudates are two different types of fluids separated in the body in reaction to other pathologies.

The transudations result from an imbalance in the oncotic and hydrostatic pressures. Transudates are generally plasma ultrafiltrates.

Exudates are the result of inflammation. Exudates are produced by various inflammatory conditions and often require more extensive evaluation and treatment than transudates.

The effusions are classified as transudates or exudates. This classification simplifies the process of arriving at a correct final diagnosis. Also, determine if more tests are needed and what other tests are needed.

Transudates are usually bilateral. They occur due to increased capillary hydrostatic pressure or decreased plasma oncotic pressure.

Exudates are usually unilateral and result from increased capillary permeability or decreased lymphatic reabsorption associated with infection, connective tissue disease, pancreatitis, or cancer.

There is an essential distinction between transudates and exudates. Transudates are caused by hydrostatic or colloidal osmotic pressure alterations, not by inflammation.

They have a low protein content compared to exudates. The medical distinction between transudates and exudates is by measuring the extracted fluid’s specific gravity.

Specific gravity is used to measure the protein content of the fluid—the greater the specific gravity, the greater the probability of capillary permeability changes in the body cavities.

For example, the specific gravity of the transudate is usually less than 1.012 and has a protein content of less than 2g / 100ml (2 g%).

The Rivalta test can be used to differentiate an exudate from a transudate. Exudates typically have a higher protein concentration and LD activity and lower pH and glucose values ​​than transudates.

It is not clear if there is a difference between transudates and exudates in the plants.


Increased capillary permeability or decreased lymphatic resorption.

Infections: bacterial, Tuberculosis, Viral.

Neoplasms: bronchogenic/ovarian / prostate carcinoma, lymphoma, hepatoma, mesothelioma, metastatic carcinoma.

Noninfectious inflammatory disease: rheumatoid disease, systemic lupus erythematosus.

  • Trauma.
  • Pancreatitis.
  • Biliary peritonitis (e.g., rupture of the gallbladder).

Exudates of plants

Plant exudates include juices, gums, latex, and resin. Sometimes, nectar is considered an exudate. The roots and seeds of plants exude a variety of molecules in the rhizosphere, including acids, sugars, polysaccharides, and ectoenzymes; this can represent 40% of the root carbon.

The exudation of these compounds has several benefits for the plant and the microorganisms of the rhizosphere.

Latex is a plant exudate found in 10% of all flowering plants.

In latex paint, the paint exhibits a common form of latex exudation, known as surfactant leaching, which occurs when water vapor condenses on the painted surface, causing the surfactants to seep out of the paint—sticky browns.