General clinical examination of pleural fluid and pericardial fluid

The internal cavities of the body - the chest and pericardial cavity - are covered with serous membranes. These membranes consist of two layers: external and internal. Between the serous layers there is a small slit-like space, forming the so-called serous cavity. Serous membranes consist of a connective tissue base and mesothelial cells covering it. These cells secrete a small amount of serous fluid, which moistens the contacting surfaces of the layers. Normally, there is practically no cavity between the serous layers. It is formed during various pathological processes associated with the accumulation of fluid. Fluids in serous cavities, accumulating during general or local circulatory disorders, are called transudates. Fluids of inflammatory origin are called exudates.

The study of the contents of serous cavities helps to solve the following problems.

• Determining the nature of the effusion being examined (exudate or transudate, i.e. whether it is formed as a result of inflammation of the serous membrane or is associated with a general or local circulatory disorder).
• Determination of the nature and etiology of inflammation in cases of inflammatory origin of effusion.

In clinical practice, the following types of exudates are distinguished.

Serous and serous-fibrinous exudates are transparent, lemon-yellow in color, contain protein (30-40 g/l) and a small number of cellular elements. They are most often detected in tuberculous pleurisy and peritonitis, para- and metapneumonic pleurisy and in relatively rare pleurisy of rheumatic etiology. The cellular composition in tuberculous pleurisy in the first days of the disease is represented by lymphocytes, neutrophils and endothelial cells, neutrophils often predominate. Subsequently, lymphocytes usually dominate.

In acute non-tuberculous pleurisy, neutrophils usually predominate in the serous exudate at the height of the disease; later, lymphocytes gradually begin to predominate. It should be noted that in rheumatism, serous (serous-fibrinous) exudate never becomes purulent. Suppuration of the exudate almost always indicates its non-rheumatic origin. Serous exudates without fibrin admixture are detected very rarely, mainly in rheumatic serositis.

Differential diagnostic signs of exudates and transudates

Research	Transudates	Exudates
Relative density	Usually below 1.015; rarely (with compression of large vessels by a tumor) above 1.013-1.025	Not less than 1.015, usually 1.018
Clotting	Doesn't coagulate	It's coagulating
Color and transparency	Almost transparent, lemon yellow or light yellow in color	Serous exudates do not differ in appearance from transudates; other types of exudates are cloudy and have different colors.
Rivalta's reaction	Negative	Positive
Protein content, g/l	5-25	30-50 (in purulent - up to 80 g/l)
Effusion/serum protein concentration ratio	Less than 0.5	More than 0.5
LDG	Less than 200 IU/L	More than 200 IU/L
LDH ratio in effusion/serum	Less than 0.6	More than 0.6
The ratio of cholesterol concentration in effusion/blood serum	Less than 0.3	More than 0.3
Cytological examination	There are few cellular elements, usually mesothelial cells, erythrocytes, sometimes lymphocytes predominate, after repeated punctures sometimes eosinophils	There are more cellular elements than in transudates. The number of cellular elements, their types and condition depend on the etiology and phase of the inflammatory process

Serous-purulent and purulent exudates. Turbid, yellow or yellow-green in color, with a loose grayish sediment, purulent exudates can be of a thick consistency. Contain a large number of neutrophils, detritus, fat droplets and almost always abundant microflora. Found in purulent pleurisy, peritonitis and pericarditis. Neutrophils always predominate in purulent exudates, the protein content is up to 50 g / l.

Putrefactive (ichorous) exudates. Turbid, have a brown or brown-green color, have an unpleasant smell of indole and skatole or hydrogen sulfide. The results of microscopic examination of putrefactive exudate are similar to those observed with purulent exudate. Putrefactive (ichorous) exudates are observed when gangrenous foci of the lung or mediastinum are opened into the pleura, when putrefactive infection from gas phlegmons of other areas of the body metastasizes into the pleura, as a complication of thoracic wounds.

Hemorrhagic exudates. Turbid, reddish or brownish-brown, contain many erythrocytes, neutrophilic leukocytes and lymphocytes are present. Protein concentration is more than 30 g / l. Hemorrhagic exudates are most often observed in malignant neoplasms, tuberculosis of the pleura, pericardium and peritoneum, injuries and gunshot wounds to the chest and hemorrhagic diathesis. Pleural exudate in a patient with pulmonary infarction, usually occurring with perifocal pneumonia, can be hemorrhagic. In such cases, detection of the hemorrhagic nature of the exudate is important for the diagnosis of pulmonary infarction, which can be masked by effusion. During the resorption of hemorrhagic exudate, eosinophils, macrophages, mesothelial cells are detected.

Chylous exudates. Cloudy, milky in color, which is caused by the presence of a large amount of fat. Under the microscope, droplets of fat, many erythrocytes and lymphocytes are determined, the presence of neutrophils is possible. The appearance of chylous exudates is associated with damage to the lymphatic vessels and the leakage of lymph into the peritoneal cavity or pleural cavity; they are detected in wounds and malignant neoplasms (in particular, in pancreatic cancer). The amount of protein is on average 35 g / l. Much less often observed are chyle-like exudates, in which fat in the pleural effusion is formed due to purulent decay of cellular elements, they have many cells with signs of fatty degeneration and fatty detritus. Such exudates are formed due to chronic inflammation of the serous cavities.

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