What we often refer to as pleural effusion is actually pleural fluid. In normal people, there is 3 to 15 ml of fluid in the pleural cavity, which plays a lubricating role during respiratory movements, but the amount of fluid in the pleural cavity is not fixed. Even in normal people, 500 to 1000 ml of fluid is formed and absorbed every 24 hours. The fluid in the pleural cavity is reabsorbed from the venous end of the capillaries, and the rest is recycled to the blood by the lymphatic system, with a dynamic balance between filtration and absorption. If this dynamic balance is disrupted for systemic or local reasons, resulting in rapid formation or slow absorption of fluid in the pleural cavity, a clinical pleural effusion will result.
What are the causes that can disrupt the dynamic balance of the pleura and produce pleural effusion? The causes actually include the following.
1, infectious pleural effusion: common, including bacteria (tuberculosis most common), fungi, parasites, mycoplasma and viruses caused by pathogenic bacteria, such as tuberculous exudative pleurisy, tuberculous abscess chest, non-specific abscess chest, pleural actinomycosis, pleural candidiasis, pleural amebiasis, pulmonary schistosomiasis pleurisy, etc.
2, malignant pleural effusion: can be pleural itself (primary) or pleural metastasis of malignant tumors from other parts (secondary), the most common metastatic cancer from lung cancer, breast cancer, ovarian cancer, gastric cancer and lymphoma, etc., primary pleural malignant tumor is pleural mesothelioma.
3, connective tissue diseases and allergic diseases: connective tissue diseases such as systemic lupus erythematosus, rheumatoid arthritis, systemic scleroderma, dermatomyositis, etc. can be accompanied by pleural effusion, there are also eosinophilic pleurisy, post-myocardial infarction syndrome, etc.
4.Other causes: including cholesterol pleurisy, tie-up pleural effusion, hemothorax and hemopneumothorax, leaky pleural effusion, etc.
How to diagnose pleural effusion? In fact, pleural effusion can be diagnosed according to different manifestations.
I. Leaky (hydrothorax) pleural effusion.
When congestive heart failure, nephrotic syndrome, cirrhosis of the liver and other forms of hypoproteinemia resulting in reduced colloid osmotic pressure and water and steel retention and cause pleural effusion; any cause of superior vena cava obstruction, the occurrence of pleural leakage effusion; some of the diseases that cause ascites, through the diaphragm lymphatic drainage into the chest cavity caused by pleural effusion. Clinical manifestations include cough, chest distension, shortness of breath and manifestations of the original disease, and signs of pleural effusion on physical examination. The pleural fluid is non-transparent, the relative density is <1.016, the protein content is below 30g/L, the ratio of pleural fluid and serum protein is less than 0.5; the lactate dehydrogenase of pleural fluid is less than 200U/L, the ratio of pleural fluid and serum lactate dehydrogenase is less than 0.6; the glucose content is similar to blood sugar; the leukocytes in pleural fluid are often completely worked than 1X10/L, and there is no pathogenic bacteria.
Second, tuberculous pleural effusion.
Tuberculous pleurisy is a highly allergic reaction of the body to the protein component of the tuberculosis bacillus, and is a consequence of primary infection or secondary tuberculosis involving the pleural membrane in children and adolescents. The onset of the disease can be acute or gradual, with fever, chest pain, dry cough, as well as symptoms of tuberculosis toxicity such as fatigue, emaciation, lack of appetite, and night sweats. In the dry pleurisy stage, chest pain increases with deep breathing and coughing, and pleural friction sound is an important sign. With the increase of pleural effusion, patients gradually feel short of breath, the pleural fluid is straw yellow transparent or boat cloudy, hairy glass, after more liberation, the fluid can be dark yellow mixed, the relative density of pleural fluid is often above 1.016, the total number of leukocytes is 1~2X10/L, the acute phase is dominated by neutrophils, the chronic phase is dominated by lymphocytes, mesothelial cells are generally less than 1%; the protein content is above 25g/L, the sugar content is more than 2.8mm. The protein content was above 25g/L, and the sugar content was below 2.8 mmol/L; the lysozyme and adenosine deaminase in pleural fluid were increased; TB bacilli were easily found in pleural fluid smear and collection, and about 1/3 of the culture method was positive. Cheese or non-cheese granuloma tissue is seen in 1/2 cases of pleural biopsy. When there are inflammatory adhesions in the pleura, encapsulated pleural effusion can be formed.
Third, malignant pleural effusion.
The primary cancer is mainly lung cancer and breast cancer, followed by lymphoma; a few are ovarian cancer, gastric cancer, uterine tumor, etc. The direct mechanisms of pleural effusion caused by tumors include pleural metastasis, which increases vascular permeability; obstruction of pleural lymphatic drainage, mediastinal lymph node obstruction of lymphatic return; obstruction of thoracic duct; obstruction of bronchial gas to reduce pleural cavity pressure; pericardial involvement (elevated vascular hydrostatic pressure, producing leakage fluid.) The sound-attached mechanisms are hypoproteinemia, obstructive pneumonia, pulmonary embolism, and complications of radiation therapy. In addition to many symptoms of tumor itself, malignant pleural effusion is often associated with shortness of breath, emaciation, chest pain, weakness and poor circulation, and can be seen on X-ray from small amounts to whole pleural effusion. Malignant pleural fluid is often bloody and grows rapidly after fluid extraction. Chest fluid examination includes routine, cytology, enzymatic changes, carcinoembryonic antigen, etc. Finding cancer cells in the pleural fluid is the basis for confirming the diagnosis of malignant pleural effusion. Since the cancer is mostly located in the dirty pleura first, and the wall pleura may only be scattered, so the positive rate of pleural biopsy is not high.
Purulent pleural effusion.
Purulent pleural effusion is abbreviated as abscess, commonly caused by lung infection (such as pneumonia, lung abscess, bronchiectasis, tuberculosis, etc.) spreading to the pleural cavity, adjacent infection (such as subseptic abscess) or sepsis, septicemia involving the pleural cavity, also as a complication of thoracic surgery, chest wall penetrating injury, tuberculous pleurisy improperly treated can become tuberculous abscess, clinical manifestations of rapid onset, with high fever, chills, dyspnea, pleural biopsy positive rate. The clinical manifestations are rapid onset, with high fever, chills, dyspnea, chest pain and wasting, cough, sputum and cyanosis, and physical signs of pleural effusion. The pleural fluid is purulent, anaerobic bacterial infection has a foul odor, the pleural fluid leukocyte count is above 2X10/L, mainly in the weeping cells, pleural fluid culture with bacterial growth, the culture should include aerobic and anaerobic, even tuberculosis culture; pleural fluid PH and sugar amount is reduced. x-ray examination can be seen pleural effusion or wrapped effusion, if there is bronchopleural fistula, the fluid plane is seen.
V. Celiac pleural effusion.
Thoracic duct rupture or obstruction, so that celiac overflow into the pleural cavity to form celiac disease, common causes of mediastinal lymph node tuberculosis or cancerous enlargement, malignant lymphoma, filarial sarcoidosis, external or thoracic surgery, etc.. Clinically acute onset, with shortness of breath and pleural effusion signs. The pleural fluid is not milky, and there is oil film formation on the surface after resting, such as ether can make the fluid clear, no odor; specific gravity of celiac fluid is 1.012~1.025, lymphocytes and red blood cells can be seen, rare granular leukocytes are alkaline PH7.4~7.8; pleural fluid has high protein content, rich in fly fat and triglyceride, higher than plasma content, but cholesterol is lower than plasma content, cholesterol/triglyceride ratio is <1.
Sixth, pleural mesothelioma.
It is a rare tumor originating from the pleural mesothelial tissue or subpleural mesothelial tissue, divided into two types: limited pleural mesothelioma and diffuse malignant mesothelioma, the latter often accompanied by plasmacytosis, plasmacythematous or hemorrhagic pleural effusion. The disease is more common in males, and the age of onset is 40-60 years old. The main manifestations are persistent dull chest pain and shortness of breath, and the symptoms are gradually aggravated, and the chest pain is not reduced by the increase of effusion; there are also signs of fatigue, emaciation, hemoptysis and other signs of pleural effusion and pleural thickening in the later stage, and the invasion of chest wall can form “frozen chest”, although there is obvious pleural thickening, but not with intercostal or hemorrhagic pleural effusion. Although there is obvious pleural thickening, but not with intercostal or chest wall depression, but with local chest wall expansion. In the late stage, with the rapid development of hemorrhagic pleural fluid, the condition becomes acute with cachexia and respiratory failure and death, the pleural fluid is mostly bloody, and the tumor cells found in the pleural fluid can be confirmed. The diagnosis can be confirmed by pleural biopsy and thoracoscopic pulling of the present pathology, and the X-ray manifestation is mainly pleural effusion or irregular pleural thickening, and the shadow of pleural thickening is sometimes “hump-like”.
Seven, connective tissue disease complicating pleurisy.
Systemic lupus erythematosus, rheumatoid arthritis, etc. are common. Pleural effusion is unilateral or bilateral, mostly in small to moderate amounts. It is often accompanied by other changes of the primary disease. In SLE, the pleural fluid is straw yellow exudate, and rarely bloody or purulent. Protein content is increased, antinuclear antibodies may be positive, immunoglobulins are increased, complement is decreased, and lupus cells can be found; anti-tuberculosis and antibiotic therapy are ineffective, and corticosteroids are effective. The rheumatoid pleural fluid is a slightly yellow or green cloudy fluid, or it can be celiac or pseudo-celiac, with a high protein content, often above 40g/L, and an increased fat and cholesterol content. The specific rheumatoid arthritis cells found in the pleural fluid are a strong basis for the diagnosis of the disease. Pleural biopsy showed non-specific inflammation, which is not significant for diagnosis.