Exudate

What is exudate?

The exudate is a liquid of variable consistency that forms during acute inflammatory processes of various kinds, accumulating in the tissue interstices or in the serous cavities (pleura, peritoneum, pericardium).

The exudate derives from the blood plasma which, following the phlogosis-dependent increase in capillary permeability, tends to escape and accumulate in the tissues.

In this effusion - typical of the acute phase - a liquid component and a solid component are recognized. This last fraction of exudate contains plasma proteins, blood cells (in particular white blood cells, platelets and - in cases of vascular lesion - red blood cells) and substances deriving from the destruction or metabolic activity of the inflamed tissue.

Why is it formed?

The purpose of the exudate is to limit the morbid process, preventing the spread of pathogens (thanks to the fibrin network), diluting any toxic substances, neutralizing the hyperacidity of the inflamed tissue and promoting the activity of leukocytes and the formation of fibrin. L " exudate also facilitates the transport of antigens to local lymph nodes, via lymphatic drainage, for the specific immune response.

Types of exudate

According to the composition, the exudate can be:

• serous: it is generally typical of milder inflammatory processes and poor in proteins; its consistency is similar to that of serum and may occasionally be found in certain diseases, such as tuberculosis.
• Fibrinous: this type of exudate, rich in fibrinogen and fibrin, is characteristic of rheumatic heart disease, but is also appreciated in rather severe inflammatory processes, such as bacterial pneumonia and streptococcal pharyngitis. The fibrinous exudate regresses with difficulty as the blood vessels grow inside it and fill the space previously occupied by the fibrin. Often it is necessary to use large quantities of antibiotics for resolution.
• Suppurative or purulent (pus): this yellowish exudate with a creamy consistency is typical of infected wounds and consists mainly of bacteria and decaying white blood cells.
• Catarrhal: this exudate is typical of the respiratory tract and is characterized by a "high concentration of mucus.

Oozed

The "exudate must not be confused with the transudate, which is not formed as a result of inflammatory processes and as such is devoid of proteins and cells.

The transudate, on the other hand, derives from the increase in venous pressure (therefore capillary), in the absence of increased vascular permeability (eg postural edema).