Clinical examination of pleural fluid and fluid in the pericardium

The internal cavity of the body - the thoracic cavity and the pericardial cavity - are covered with serous membranes. These shells consist of two sheets: the outer and the inner. Between the serous leaves there is a small slit-like space that forms the so-called serous cavity. Serous membranes consist of a connective tissue base and mesothelium cells covering it. These cells secrete a small amount of serous fluid, which moistens the contacting surfaces of the leaves. In norm between serous leaves the cavity is practically absent. It is formed with various pathological processes associated with the accumulation of fluid. Fluids in the serous cavities, accumulating in the presence of general or local circulatory disorders, are called transudates. Fluids of inflammatory origin are called exudates.

The study of the contents of serous cavities contributes to the solution of the following problems.

• Determination of the character of the studied effusion (exudate or transudate, that is, whether it is formed due to inflammation of the serosa or is associated with impaired circulation of general or local character).
• Determination of the nature and etiology of inflammation in cases of inflammatory origin of effusion.

In clinical practice, the following types of exudates.

Serous and serous-fibrinous exudates are transparent, lemon-yellow, contain protein (30-40 g / l) and a small number of cellular elements. Most often they are detected with tubercular pleurisy and peritonitis, para- and metapneumonic pleurisy and with relatively rare pleurisy of rheumatic aetiology. Cellular composition with tuberculous pleurisy in the first days of the disease is represented by lymphocytes, neutrophils and endothelial cells, neutrophils often prevail. In the following, lymphocytes usually predominate.

In acute tuberculosis pleurisy in serous exudate at the height of the disease, neutrophils usually prevail; later, lymphocytes gradually begin to predominate. It should be noted that with rheumatism, serous (serous-fibrinous) exudate never passes into a purulent exudate. Suppuration exudate almost always speaks of its non-rheumatic origin. Serous exudates without an admixture of fibrin are detected very rarely, mainly with rheumatic serosites.

Differential and diagnostic signs of exudates and transudates

Research	Transudates	Exudates
Relative density	Usually below 1.015; rarely (when the large vessels are compressed by a tumor) is higher than 1,013-1,025	Not less than 1.015, usually 1.018
Clotting	Do not clot	Collapses
Color and transparency	Almost transparent, lemon yellow or light yellow	Serous exudates do not differ in appearance from transudates, other types of exudates are turbid, color is different
Revalta reaction	Negative	Positive
Protein content, g / l	5-25	30-50 (in purulent - up to 80 g / l)
The ratio of protein concentration in the sweat / serum	Less than 0.5	More than 0.5
LDH	Less than 200 IU / L	More than 200 IU / liter
The LDH ratio in the sweat / serum	Less than 0.6	More than 0.6
The ratio of the concentration of cholesterol in the sweat / serum	Less than 0.3	More than 0.3
Cytological examination	Cellular elements are few, usually mesothelial cells, erythrocytes, sometimes lymphocytes predominate, after repeated punctures, sometimes eosinophils	Cellular elements are larger than in transudates. The number of cellular elements, their types and condition depends on the etiology and phase of the inflammatory process

Serous-purulent and purulent exudates. Muddy, yellow or yellow-green, with a loose grayish deposit, purulent exudates can be a thick consistency. Contain a large number of neutrophils, detritus, fat drops and almost always abundant microflora. Discovered with purulent pleurisy, peritonitis and pericarditis. In purulent exudates neutrophils always prevail, the protein content is up to 50 g / l.

Putrefactive (ichoric) exudates. Muddy, have a brown or brownish-green color, have an unpleasant smell of indole and skatole or hydrogen sulphide. The results of microscopic examination of putrefactive exudate are similar to those observed with purulent exudate. Putrefactive (ichoric) exudates are observed when the lungs or mediastinum gangrenous fossae are opened in the pleura, when the putrefactive infection from the gas phlegmon of other areas of the body is metastasized into the pleura, as a complication of thoracic wounds.

Hemorrhagic exudates. Muddy, reddish or brownish brown, contain a lot of red blood cells, neutrophilic leukocytes and lymphocytes are present. The protein concentration is more than 30 g / l. More often hemorrhagic exudates are observed in malignant neoplasms, with pleural tuberculosis, pericardium and peritoneum, traumas and gunshot wounds of the chest and hemorrhagic diatheses. Hemorrhagic can be pleural exudate in a patient with a lung infarction, usually occurring with perifocal pneumonia. In such cases, the detection of the hemorrhagic nature of the exudate is important for diagnosing an infarct of the lung, which can be masked by effusion. During the resolution of hemorrhagic exudate, eosinophils, macrophages, mesothelial cells are found.

Chillious exudates. Muddy, milky, which is caused by the presence of a large amount of fat. Under the microscope, droplets of fat, many erythrocytes and lymphocytes are detected, possibly the presence of neutrophils. The appearance of chyleous exudates is associated with damage to the lymphatic vessels and the flow of lymph into the cavity of the peritoneum or the pleural cavity; they are detected in wounds and malignant neoplasms (in particular, in pancreatic cancer). The amount of protein on average 35 g / l. Hylus-like exudates are much less common, in which fat in the pleural effusion is formed due to purulent decomposition of cellular elements, they contain many cells with signs of fatty degeneration and fat detritus. Such exudates are formed due to chronic inflammation of the serous cavities.

[1], [2], [3], [4], [5], [6], [7], [8]