The study of serous fluids (they are also called effusion) has great diagnostic value in modern medicine. Information about these studies enables the doctor to establish a diagnosis and prescribe effective treatment in a timely manner. So let's figure out what it is, what types of serous fluid are and with what diseases they can be detected.
general information
Exudative fluid is ultrafiltrate of human blood. This means that this substance is formed due to the filtration of blood from the bloodstream into the surrounding cavities and tissues. Moreover, in the classical sense, effusion is a fluid that accumulates in the cavities of the human body. And what is collected in the tissues is called edematous fluid.
Normally, only part of the blood with a low molecular weight (water and electrolytes, for example) is able to pass through the pores of the capillaries. And substances with a high molecular weight (proteins, formed elements) must remain in the bloodstream. However, if there is an inflammatory process in the body, the wall of the blood vessels is damaged, and large molecules of proteins and blood cells can enter the body cavity.
The concepts of serous cavities and membranes
The serous cavity is a space bounded by serous membranes.
Serous membranes are films consisting of two sheets: parietal (located closer to the muscles) and visceral (tightly covering the internal organs).
The leaves of the serous membranes are represented by the following layers:
- mesothelium;
- boundary membrane;
- fibrous collagen layer;
- surface network of elastic fibers;
- deep longitudinal network of fibers;
- trellised layer of collagen fibers.
Mesothelium in the composition of the serous membranes has an important function: its cells constantly produce the fluid necessary for depreciation.
The visceral (organ) leaf of the serous membrane receives blood from the vessels supplying the organ that it covers. A parietal leaflet receives blood supply from a wide network of anastomoses.
The serous membranes have a well-developed outflow of lymph. Therefore, the slightest violation of the lymphatic outflow can lead to the accumulation of serous fluid.
Main functions
Why does a person need the presence of serous fluids in the cavities? To answer this question, we highlight the main functions of the effluent fluid:
- protective function - prevention of friction of organs against each other and their trauma;
- providing dynamic properties of internal organs;
- sliding-depreciation function, as one of the components of the protective.
Types of effluent
Exudative fluid is divided into two main types: transudate and exudate.
Transudate is a fluid whose accumulation is not associated with the presence of an inflammatory process in the body. If it is collected in tissues, this condition is called edema.
If transudate is collected in the pericardium (cardiac sac), hydropericardium is observed, if ascites is in the abdominal cavity, hydrothorax in the pleural cavity, and hydrocele around the testicle.
Exudate is a fluid that collects in the body cavity due to an inflammatory process.
Thus, although transudate and exudate are two varieties of the same process, they have a completely different origin, and, consequently, structure.
Transudate: causes of accumulation
The accumulation of serous fluid in the form of transudate can be caused by the following pathological conditions:
- hypoproteinemia - a decrease in the concentration of protein in the blood, mainly due to albumin; observed with glomerulonephritis with nephrotic syndrome, severe liver disease with the development of hepatic cell failure, general depletion of the body;
- violation of the outflow of lymph with blockage of the lymphatic vessels;
- increase in venous pressure, which occurs with cardiovascular failure, severe liver and kidney diseases.
- an increase in the concentration of sodium in the blood, is observed with heart failure, nephrotic syndrome, liver failure.
- increased synthesis of aldosterone, which leads to increased absorption of sodium and water in the kidneys.
Exudate: types
When diagnosing a type of serous fluid and confirming the presence of exudate, it is necessary to indicate which type is found:
- serous - has a transparent or cloudy appearance, white;
- serous-purulent, or purulent - cloudy, yellow-green in color with sediment;
- putrefactive - cloudy with a pungent odor;
- hemorrhagic - red or red-brown;
- chylous - cloudy yellowish;
- cholesterol - a thick yellow liquid with cholesterol flakes;
- mucous - with a large amount of mucin;
- fibrinous - includes fibrin filaments;
- mixed forms - serous-fibrinous, mucopurulent, etc.
Transudate and exudate: differences
The differences in these two effluent fluids are based on their concentration of protein, glucose, the specific gravity of the two fluids, and also on their macroscopic characteristics (color, transparency).
As noted above, the accumulation of transudate in the cavities is in no way associated with inflammation. Therefore, the presence of differences between these two types of effusions is quite logical.
Let's start with the specific gravity. In exudate, it is much higher than in transudate, amounting to> 1.015 and <1.015, respectively.
The protein level in the transudate is also less than in the exudate - a truly protein fluid. Its concentration is <30 g / l for transudate and> 30 g / l for exudate.
There is a special test to distinguish these two types of effusions. It is called a breakdown of Rivalt. Despite the fact that this test has been used in medical practice for more than 60 years, it is still widespread when it is necessary to differentiate two types of serous fluids. Its main advantage is the speed of obtaining the result. Here the difference between transudate and exudate is that in the presence of transudate, the sample is negative (which cannot be said about exudate).
| Transudate | Exudate |
| Specific gravity | 1.006–1.015 | more than 1,015 |
| Protein concentration | less than 30 g / l | more than 30 g / l |
| The presence of bacteria | Not characteristic | Characterized by the presence of bacteria (streptococci, staphylococci, etc.) |
| Cells that are detected in sediment | Mesothelium, lymphocytes, there may be a small number of red blood cells | Neutrophils, lymphocytes, a large number of red blood cells and macrophages, eosinophils, tumor cells |
| The ratio of the concentration of effluent protein to the concentration of blood protein | <0.5 | > 0.5 |
| Glucose concentration (mmol / l) | > 5.3 | <5.3 |
| Cholesterol Concentration (mmol / L) | <1.6 | > 1.6 |
| The number of cells, the term "cytosis" is used in medicine | <1 × 10 9 / L | > 1 × 10 9 / L |
Thus, the ability to distinguish between transudate and exudate is very important for the doctor. After all, this contributes to the establishment of a correct diagnosis, and therefore to the appointment of the right treatment.