Pleural effusion

Definition

The term "pleural effusion", extracted from medical language, refers to an excessive accumulation of fluid inside the pleural cavity. In physiological conditions, the pleural cavity contains no more than 10-20 ml of fluid; the pleural effusion is an expression of an inadequate disposal or an exaggerated production of this pleural fluid. Before proceeding with the analysis of the disease, let us clarify some concepts, useful for better understanding the distinctive characteristics of the disease.

Terminology

PLEURA: thin layer of connective tissue with the function of supporting and lining the lungs. The pleura is a serous membrane consisting of two sheets: the visceral pleura is the innermost sheet that adheres to the external lung wall, while the parietal pleura lines the thoracic cavity (from the inside) and the upper face of the diaphragm

PLEURAL CABLE: very thin virtual space interposed between the visceral pleura and the parietal pleura

PLEURIC LIQUID: enclosed in the pleural cavity, it has a lower pressure than the ambient one. A right amount of liquid is essential to ensure the sliding of the two pleural membranes, while ensuring their union.In physiological conditions, the presence of pleural fluid prevents the lung from collapsing (collapse is a typical event of pneumothorax)

Statistics and Causes

Pleural effusion can be an indicator of a "disease affecting the pleura, lung or extrapulmonary lesions.

Pleural effusion is a pathological condition common to most forms of pleurisy (inflammation of the pleura).
The presence of a pleural effusion malignant it can be a complication of various cancers: in the USA, for example, the average annual incidence is 150,000 patients. Medical statistics show that pleural effusion occurs in 7-15% of patients with primary lung cancer. Breast cancer, lymphoma and thoracic neoplasms can predispose the patient to pleural effusion.
Together with empyema (collection of purulent fluid inside the pleural cavity) and lung abscess, pleural effusion is often found in numerous clinical pathologies that increase mortality.
Pleural effusion can also result from virus-borne infections, in particular Shingles, Morbillivirus, Paramyxovirus And Orthomyxovirus (influenza and parainfluenza viruses).

Classification

It is necessary to distinguish two main types of pleural effusion: exudate and transudate. Let us briefly recall that blood, pus or pounds can also accumulate in the pleural space.

1. Pleural effusion of the TRANSUDATIVE type: occurs in case of rupture of the hydrostatic * and oncotic ** forces, operating through the pleural and capillary membranes. In the presence of transudate, the pleurae are healthy. Transudative pleural effusion can result in:
   • Cirrhosis
   • Peritoneal dialysis
   • Hypoalbuminemia
   • Left ventricular failure
   • Pulmonary embolism, hypothyroidism, mitral stenosis (less frequently)
2. Exudative pleural effusion: typical expression of an infectious-inflammatory process, the exudate is formed in case of greater permeability of the pleural surface and / or capillaries. The exudative pleural effusion can be favored by:
   • Lung cancer and breast cancer (often times)
   • Pneumonia (very common)
   • Rheumatoid arthritis, asbestos exposure, pancreatitis, tuberculosis (less frequently)
   • Fungal infections (rare)

Terminology:

* Hydrostatic pressure: force exerted by the fluid on the surfaces it comes into contact with. An increase in hydrostatic pressure, common in the presence of hypertension, favors the accumulation of pleural fluid through increased filtration.

** Oncotic pressure: osmotic pressure exerted by proteins dispersed in solution in the plasma. The oncotic pressure is therefore heavily influenced by the concentration of proteins in biological fluids: when this decreases, the oncotic pressure also decreases and the pleural fluid increases due to the reduction of its reabsorption.

How it forms

Pleural effusion may be due to an exaggerated increase in hydrostatic pressure and capillary permeability, a drop in oncotic blood pressure, a reduction in pressure in the pleural space, and a marked inefficiency of lymphatic drainage.

Pleural effusion:
↑↑ hydrostatic pressure and capillary permeability → typical of heart failure and inflammation
↓↓ oncotic plasma pressure → typical of hypoalbuminemia, nephrosis syndrome, liver cirrhosis
↓↓ pressure in the pleural space → lung retraction
Malfunction of lymphatic drainage → typical of neoplasms and fibrosis

Fluid passage from the peritoneal space to the pleural cavity → ascites

As a typical consequence of ascitic effusions (collection of fluid in the peritoneal cavity), the pleural effusion can also be favored by the passage of fluid from the peritoneum.

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Pleural effusion: symptoms, diagnosis and therapy "