Pleural effusion is an accumulation of fluid of a different nature in the pleural space of cats. The pleural space is the gap between the two feline pleurae, which line the lung and aid in breathing. For this reason, an abnormal accumulation of fluid in this cavity causes cats to have respiratory distress, which causes them to become agitated and increase their respiratory rate. Pleural effusion, more than a disease in itself, is a clinical sign of other feline diseases and pathological processes, so a good diagnosis is the key to knowing the origin of the effusion and the analysis of the liquid since, among other diagnostic tests, help find out.
What is pleural effusion?
Pleural effusion is an abnormal accumulation of fluid of various kinds in the pleural space, which is the space between the visceral pleura (membrane that covers the lungs) and the parietal (the one that covers the walls of the thorax, mediastinum and diaphragm) and that naturally contains a minimum amount of fluid to lubricate the lungs during respiratory movements.
A disorder in the production or elimination of this fluid causes an excessive accumulation of it in the pleural space, which causes a restriction of lung movement during inspiration(lung expansion) which can cause the lobes of the lung to collapse.
In general, pleural effusion in cats can be caused by any of the following mechanisms:
- Increased capillary permeability.
- Reduction of the oncotic pressure of the capillaries.
- Increased hydrostatic pressure in capillaries.
- Lymphatic obstruction.
Types of pleural effusion in cats
Pleural effusion in cats can be of various types depending on the nature of the fluid accumulated in the pleural space. The liquid must be analyzed and, according to a series of characteristics and parameters, we can divide it into the following types:
- Pleural effusion of pure transudate: the color of the liquid is clear or yellowish, with little protein (<2, 5 gr/ dl), without fibrin and low cellularity (<1,000 cells/microliter).
- Pleural effusion of modified transudate: with a yellowish-pink color, somewhat cloudy, has a protein quantity between 2, 5 and 5 gr/dl, without fibrin, triglycerides or bacteria and with a cell count of 1,000-15,000 cells/microliter (reaching 100,000 if produced by lymphosarcoma) and with mesothelial cells, non-degenerated neutrophils and neoplastic cells in lymphosarcoma. You may also be interested in taking a look at this other post on our site about Lymphoma in dogs, its treatment and life expectancy.
- Pleural effusion of inflammatory exudate: with the same color as the previous one, the amount of protein is 2.5-6 gr/dl, even reaching 8.5 gr/dl in the case of FIP and the presence of fibrin but without triglycerides or bacteria and a cell content of 1,000-20,000 cells/microliter (reaching 100,000 if produced by lymphosarcoma) and with non-degenerated neutrophils, macrophages and neoplastic cells in tumors.
- Pleural effusion of septic exudate: with a yellowish-brown color and cloudy or opaque, total proteins are 3-7 gr/ dl and contains fibrin, bacteria but no triglycerides. The cell count is 5,000-300,000 cells/microliter and contains degenerated neutrophils, macrophages and bacteria.
- Pleural effusion of lymph: the color in this case is milky-white (although it can sometimes be pinkish-reddish) with a amount of proteins of 2, 5-6 gr/dl and with fibrin, triglycerides and without bacteria. The cell content is 500-20,000 cells/microliter and usually contains lymphocytes, neutrophils and macrophages.
- Pleural blood effusion: the color is red and opaque, with more than 3 gr/dl of protein and with fibrin but without triglycerides or bacteria, with a cell count similar to that of peripheral blood and with red blood cells and some bank blood cells.
Causes of pleural effusion in cats
There are many causes that can produce an accumulation of fluid in the pleural space of cats. In general, any of the following diseases and disorders can cause feline pleural effusion:
- Hepatic disease: due to the development of hypoproteinemia that reduces oncotic pressure and allows the outflow and accumulation of fluid in the pleural space.
- Kidney disease (glomerulonephritis): due to loss of protein in the urine. Discover here 4 symptoms of kidney disease in cats.
- Enteropathy: due to protein loss in the intestine.
- Congestive cardiomyopathy: due to congestive heart failure in diseases such as congenital heart defects, feline dirofilariosis, hypertrophic cardiomyopathy or pericardial diseases. You can find more information about feline hypertrophic cardiomyopathy, its symptoms and treatment in this other post on our site.
- Wet Feline Infectious Peritonitis (FIP): Due to immune vasculitis, causing damage to the endothelium of blood vessels and leakage of capillary proteins and serum. The exudate is nonseptic fibrinous (nonbacterial). To learn more about Feline Infectious Peritonitis (FIP), its symptoms and treatment, do not hesitate to consult this article.
- Bacterial infections: can cause accumulation of pus (pyothorax) due to the entry of bacteria through bites and wounds, perforation of the ecophagus or the trachea, extension of pneumonia, pin penetration, severe periodontal infection, etc.
- Tumors in the mediastinum: such as lymphosarcoma, thymoma, hemangiosarcoma or breast tumors.
- Tumor in the lung (adenocarcinoma): either primary or secondary due to metastasis from another location.
- Diaphragmatic hernia: due to the trauma or accident that caused it.
- Pulmonary lobe torsion right or left middle.
- Thoracic trauma: due to lung injury or rupture of blood vessels in the chest, it produces pleural effusion of blood (hemothorax), as well as in rodenticide poisoning (coagulopathy).
Symptoms of pleural effusion in cats
Clinical signs of pleural effusion in the cat are generally as follows:
- Dyspnea or difficulty breathing.
- Reduced lung sounds due to fluid.
- Increased respiratory rate or tachypnea.
- Tos: for more information on Cough in cats, symptoms, causes and treatment, read this post that we suggest.
- Exercise intolerance.
- Anorexia and weight loss: don't hesitate to take a look at this article on Anorexia in cats, its causes, symptoms and treatment.
In addition, depending on the disease or condition that caused it, the cat will present symptoms associated with the process. For example:
- In conditions that result in congestive heart failure: Cats will also have hypothermia, a weak pulse, and jugular vein distention, as well as as well as they can present an increase in the size of the liver and ascites. You may be interested in this article that we recommend about Hypothermia in cats, its causes, symptoms and treatment.
- In cases of feline infectious peritonitis: depression, fever and jaundice (yellowing of the mucous membranes), neurological signs and ocular. We suggest you consult this article to find out if My cat is depressed, the causes, symptoms and treatments.
- In the case of mediastinal tumors: regurgitation and dysphagia may also appear due to compression of the esophagus, Horner's syndrome if the chain is compressed sympathetic swelling of the neck and head if the cranial vena cava is compressed, reduced heart and lung sounds, and distention of the jugular vein. If you didn't know about Horner's Syndrome in cats, its causes and treatment, we leave you this article so you can find out.
- In the case of glomerulonephritis: Cats will show signs of kidney disease such as increased urination and water intake, pale mucous membranes, vomiting or uremic syndrome, among others.
- In case of liver disease: jaundice, increased liver enzymes and ascites may be seen and in protein-losing enteropathy Edema and ascites can also be seen, as well as thromboembolic disease due to the loss of antithrombin at the intestinal level.
Diagnosis of pleural effusion in cats
The first thing to do is a thorough history by questioning the caretaker of the sick cat and a physical examination of the cat to note clinical signs, body condition, respiration, auscultation, and mental status.
With symptoms such as shortness of breath, tachypnea, and reduced lung sounds, the diagnosis of pleural effusion is very likely. In an x-ray the presence of fluid can be evidenced in the pleural space by preventing normal visualization of the lungs and with the ultrasound it is possible to suspect or deduce what type of fluid es (transudate, blood, lymph, pus), obtaining clear information with the analysis of the liquid after a thoracocentesis by cell count, cytology and biochemistry. If infection is suspected, the fluid should be cultured.
Other ways of diagnosing pleural effusion in cats are:
- Electrocardiogram: to assess heart function and detect arrhythmias and tests for FIP virus in suspected cases of this infectious disease.
- Blood tests, biochemistry and urinalysis: they are essential to rule out kidney, liver or digestive causes and observe the state general he alth of the cat.
Treatment of pleural effusion in cats
Pleural effusion therapy will depend on the originating cause Even so, emergency treatment includes oxygen therapy due to the respiratory distress, thoracentesis or puncture of the pleural space to drain the fluid and at the same time take samples of it for analysis and diuretics such as furosemide or spironolactone to reduce the stress of the cat, although it depends on the origin of the cause.
- In tumors: chemotherapy should be used and, in some tumors, diaphragmatic hernias and torsion of the pulmonary lobe, the treatment will be surgical.
- In case of pyothorax: the infection that is causing the accumulation of pus in the pleural space should be treated with antibiotics. In chylothorax due to accumulation of lymph in the pleural space, the chyle should be drained frequently by thoracocentesis or by placing a drainage tube in the cat. If this is not effective, surgical treatment should be considered with ligation of the thoracic duct after draining. the lymph from the pleural cavity.
If heart failure is evident, in addition to diuretics and oxygen, drugs such as nitroglycerin or digoxin can be used. In kidney, liver and intestinal disease, an effective therapy should be adapted to control these pathologies.
Sequelae of pleural effusion in cats
Pleural effusion in cats can leave sequelae although, generally, with proper therapy and diagnosis of the problem, cats maintain their he alth and quality of life as before the effusion. Among the main sequelae of pleural effusion in cats we find:
- Damage at the lung level such as pulmonary edema.
- Poorly resolved infection that develops into a chronic abscess called an empyema.
- Air in the chest cavity or pneumothorax after thoracentesis.
