In our study, 275 cases of exudative pleural effusion and 307 cases of exudative pleural effusion were included. The ultrasonic imaging characteristics of every case were analyzed retrospectively. The results showed that: in 275 cases of exudative pleural effusion, 140 cases had light spots (50.9%), 131 cases had septa (47.6%), 161 cases had low echo (58.5%) The pleural thickening was more than 3 mm in 109 cases (39.6%). There was a difference in the proportion of patients with the above manifestations between the two groups (P < 0.05). According to the etiology of exudative pleural effusion, the results showed that compared with other diseases, the proportion of pleural effusion in empyema patients with light spots, separation, low echo and pleural thickening was higher, which were 87.8%, 100%, 82.9% and 73.2% respectively.
Exudative pleural effusion is mostly caused by diseases that increase pleural permeability, such as tuberculosis, pneumonia, rheumatic diseases, pleural metastasis of lung cancer, mesothelioma. The main diseases included in this study include pneumonia, tuberculosis, lung cancer and rheumatic diseases. Parapneumonic pleural effusion is a common complication of community-acquired pneumonia, mainly due to inflammation involving the pleura . According to laboratory examination and clinical characteristics, parapneumonic pleural effusion (PPE) can be divided into uncomplicated parapneumonic pleural effusion (UPPE), CPPE and empyema . The patients included in this study were CPPE and empyema. The former accounted for 62.4% and the latter 37.6%. Compared with UPPE, CPPE had higher protein, LDH and CRP, but lower glucose and PH . The progress of PPE can be divided into three stages: stage I is the exudative stage, with low content of inflammatory cells and good fluidity; stage II is the fibrous purulent stage, with deposition of fibrin and fibrous septum; stage III (tissue organization stage) with fibrous cell proliferation and pleural thickening [15–16]. This study also confirmed the characteristics of CPPE and empyema from the ultrasound images: the probability of light spot, separation, low echo and pleural thickening is high, and these features are more obvious in empyema. Tuberculous exudative pleurisy is an extrapulmonary disease caused by the entry of Mycobacterium tuberculosis into the pleural cavity . Due to the high reaction of the pleura to the tuberculous toxin, it is easy to form exudate, and the effusion is characterized by high lymph component and high protein content (> 3g/10ml) . Tuberculous pleural effusion has high fluidity in the early stage, but because of its high protein content, the viscosity of pleural effusion increases and tissue adheres with time, then reticular separation will form. After pleural effusion is gradually absorbed, the cell composition increases relatively, which will be shown as strong light spots on ultrasound [19–20]. In an analytical study on the ultrasonic manifestations of 18 patients with tuberculous pleurisy, 100% of the patients with pleural effusion showed separation, and pleural thickening was demonstrated in 6 cases . In our study, 86 cases of tuberculous exudative pleurisy were obtained, 36% of the patients’ ultrasound performances showed light spots, and 33.7% of the patients’ ultrasound performances showed separation, the ratios were lower than the previous study.
Lung adenocarcinoma is an important cause of pleural effusion . 90% of the patients with cancer included in our experimental group are lung adenocarcinoma, 65.2% of them are primary diagnosis and treatment (45 cases), 34.8% are pleural effusion after chemotherapy (24 cases). Because of the extensive invasion of malignant tumor cells, the pleura adjacent to pleural effusion was damaged in a large area, thus the malignant pleural effusion is rich in plasma protein, inflammatory cells, epithelial cells and tumor cells secreted proteins . Compared with the patients with primary malignant pleural effusion, the malignant pleural effusion in patients receiving treatment will be gradually absorbed with the progress of chemotherapy, and the component of protein will be relatively increased, then separation and wrapping will be formed [24–25]. Ultrasonic images will be reflected accordingly. From our statistical results, 45 patients were initially diagnosed, only 2 cases showed signs of separation, while 66.7% of patients with pleural effusion after chemotherapy showed a separation, compared with the former, there was an upward trend. The pulmonary diseases caused by rheumatism mainly include interstitial lung disease, alveolar disease, pulmonary artery disease, etc. Main rheumatisms that cause pleura disease are SLE and RA . Pleural effusion occurs in about 24% of SLE patients. This be related to lupus pleurisy, the biochemical examination of which shows multi-nuclear cells are dominant in acute stage, while monocytes are the main ones in chronic stage. Pleural effusion absorption can be repeated, and finally left pleural thickening .
The incidence rate of pleural effusion caused by RA is as high as 38–73% . Pleural effusion in RA patients has high LDH and protein content, and the content of sugar is obviously reduced. Monocytes and multinucleated cells are the main in pleural effusion. Pleural effusion can be repeatedly produced and encapsulated, forming parcels and adhesion eventually . 11 patients with rheumatic diseases were included in this study, of which 4 cases had separation in the pleural effusion and 8 had echo, which was in line with the characteristics of rheumatic pleural effusion.
Leakage of pleural effusion is mainly caused by body circulation or low colloid osmotic pressure in the pulmonary circulation, retention of water and sodium, obstruction of venous return, pleural membrane itself has no pathological changes . The leakage liquid is mostly clear and transparent liquid, colorless or light yellow, low protein quantity, low cell count and no bacterial infection . With the progress of the disease, the routine and biochemical changes of the leakage liquid will not be obvious. In our study, the ultrasound images of the control group showed that most of the cases had no adhesion, wrapping, light spot, pleural pathological hypertrophy and other characteristics. It should be pointed out that in the control group of heart failure cases, ultrasound showed that 9 patients had weak light spots in pleural effusion, 3 patients had a small amount of separation, 1 patient had low echo, 1 patient had pleural thickening, which may be related to patients with long-term recurrent heart failure, pulmonary congestion, concurrent infection, and a small amount of exudative components in pleural effusion.
In general, through the collection and collation of large sample information, we found that ultrasound has auxiliary diagnostic value in exudative pleural effusion. If there are light spots, separation, pleural thickening and other signs in pleural effusion, pleural effusion is likely to be exudative.