Pleural effusion refers to the presence of excessive fluid retention in the pleural cavity of cats. Normally, cats have less serous fluid in their chest cavity. Generally no more than 2 ml, it has the effect of lubricating the pleura and reducing the friction between the lung and the pleura parietal during breathing. Pleural effusion occurs when the balance between the formation and absorption of pleural fluid is out of balance.

The pleural cavity is a closed cavity composed of the parietal pleura and the visceral pleura. There is a small amount of fluid between the layers of pleura to reduce the friction between the two layers of pleura during breathing activities, which is conducive to the relaxation and contraction of the lungs in the thoracic cavity.

According to the characteristics of pleural effusion, pleural effusion can be divided into pure exudate, modified exudate and exudate. Laboratory sample testing plays a crucial role, as different types of effusion can be caused by different or the same disease, but it still provides the basis for further differential diagnosis of the disease. Exudates and modified exudates can be secondary to increased intrapleural hydrostatic pressure, decreased colloid osmotic pressure, and/or increased vascular permeability, while increased pleural capillary wall permeability and parietal pleural lymphatic drainage are more common lead to exudate. Thoracic trauma is the main cause of empyema and hemothorax.

Chylous pleural effusion is more common in cats clinically, and its characters are: cloudy, opaque, milky; specific gravity > 1.025, protein > 20g/L, The number of cells is 1000-17000/ul (mainly small lymphocytes). When the effusion sample meets the above conditions, and the effusion triglyceride > plasma triglyceride, effusion cholesterol < plasma cholesterol, it can be determined as chyle .

I. Diagnosis:

Comprehensive evaluation of heart and respiration function to help diagnose pleural effusion.

1. General examination 

Standing or lying in the chest position, percussion on the chest wall Both sides were horizontally dulled. On chest wall auscultation, heart sounds and lower lung breath sounds were significantly reduced, heart murmurs and arrhythmias were present in some animals, and bronchoalveolar sounds were enhanced in the upper chest wall.

2. Pleural puncture 

The pleural puncture point is usually selected in the sixth -8 Intercostal, rib and costal cartilage connection below the horizontal line. However, it should be noted that when the puncture needle punctures the pleura, the needle should be placed against the chest wall immediately, and the needle tip shoe should be kept inward, which is conducive to drainage of effusion and avoids damage to the expanded lung. The collected puncture fluid was treated with anticoagulation, non-anticoagulation and direct smear, so as to facilitate the serial examination of cells, bacteria and biochemistry.

3. X-ray examination 

X-ray side view can see the chest There is a uniform horizontal shadow in the lower part; the shadow of the heart is blurred, and the angle of the heart and diaphragm is blunted or disappeared; the interlobar fissures are widened, and the edge of the lung near the sternum becomes fan-shaped. X-ray images of dorso-ventral or ventro-dorsal can widen the mediastinum, the lung border is far away from the chest wall, the costophrenic angle increases, and the lung border becomes rounded.

Second, treatment:

It is recommended to perform thoracentesis The test of thoracic fluid and puncture fluid samples is an important basis for determining the cause. It is best to perform thoracentesis under the guidance of ultrasound to avoid accidental damage. It will cause the displacement of the anatomical position of the organs. For emotional cats, sedative drugs can be injected in advance according to the situation. Some diseases are incurable (eg, tumors, heart disease), and pleural effusion will recur. Doctors need to adjust medication or increase diuretics according to the underlying cause, and perform thoracentesis regularly. For purulent pleural effusion, it is recommended to place a thoracic duct for pleural fluid drainage, supplemented by irrigation and targeted treatment, and surgical methods can also be used to remove the cause to achieve curative effect.