What causes pleural effusion and ascites? Why does ascites occur?

There is a certain amount of water in the chest and abdomen of the human body. The water in the chest and abdomen can lubricate the intestines and help gastrointestinal digestion, but if there is too much water in the chest and abdomen, it will lead to ascites. Ascites is caused by excessive water accumulation in the chest and abdomen, which will cause some uncomfortable reactions in the body and affect the stability of the body's internal environment. Next, I will give you a detailed introduction to the causes of behavioral ascites.

Pleural effusion is a closed cavity composed of parietal pleura and visceral pleura, with negative pressure inside. Under normal circumstances, there is a small amount of liquid (about 1 to 30 ml) between the two layers of pleura, which acts as a lubricant, reducing the friction between the two layers of pleura during respiratory activities and facilitating the contraction and relaxation of the lungs in the chest cavity. This fluid is produced by the parietal pleura and absorbed by the visceral pleura. It circulates continuously in a dynamic balance and the amount of fluid remains constant.

When something happens that affects the pleura, whether it is the change in the rate at which the parietal pleura produces pleural effusion or the change in the rate at which the visceral pleura absorbs pleural effusion, the fluid in the pleural cavity can increase, which is called pleural effusion (effusion).

It was previously believed that the exchange of pleural effusion depends entirely on the pressure difference between the hydrostatic pressure of the fluid and the colloid osmotic pressure. In animals with thin visceral pleura (such as rabbits), the parietal pleura is mainly supplied by the intercostal arteries, and the capillary pressure is high, while the visceral pleura is supplied by the pulmonary arteries, and the capillary pressure is low. Therefore, driven by pressure, the fluid is filtered from the parietal pleura into the pleural cavity, and the visceral pleura reabsorbs the pleural effusion at a similar pressure.

However, since the 1980s, due to the discovery of lymphatic micropores between the parietal pleural mesothelial cells of animals with thick visceral pleura (including humans), and the discovery that the visceral pleura is supplied by the systemic bronchial arteries and pulmonary circulation, a consensus has been reached on the mechanism of pleural effusion production and absorption, namely, pleural effusion enters the pleural cavity from the systemic circulation vessels of the parietal and visceral pleura through the leaky pleura due to the pressure gradient, and is then reabsorbed through the lymphatic micropores of the parietal pleura via the lymphatic vessels, a form similar to any interstitial cavity in the body. Under normal circumstances, the visceral pleura has little effect on the circulation of pleural effusion.

Pleural effusion can be divided into exudative and transudative types based on its nature. There are many causes of exudative diseases, which can be summarized into two categories: one is caused by inflammatory lesions, such as infectious inflammation caused by bacteria, viruses or fungi infecting the pleura, leading to pleural effusion, or pleural effusion caused by non-infectious inflammation such as pulmonary embolism, pancreatitis, connective tissue disease, etc.; the second is tumor-related, such as cancer growing in the pleura or metastasizing and invading the pleura, causing effusion, which can be seen in pleural mesothelioma, lung cancer, breast cancer, gastric cancer, etc. The cause of transudative pleural effusion may be systemic diseases, such as hypoproteinemia, allergic diseases, or lesions of certain organs, such as congestive heart failure, cirrhosis, hepatic amebiasis, thoracic duct rupture, etc.