Pleural effusion

A pleural effusion is a pathological accumulation of fluid in the pleural space. It is a common disease with a multitude of recognized causes including local diseases of the pleura, the underlying lung, systemic diseases, organ or drug dysfunction; the most common being heart failure. The concept is frequently related to the manifestation of an inflammation of the pleura (pleurisy).

The pleura is a membrane that surrounds the lung and, under normal conditions, contains a small amount of fluid (between 10 and 20 ml in healthy adults). This liquid acts as a lubricant and aims to facilitate the movement of the lung in breathing. The proper amount of it is maintained through a balance of hydrostatic and oncotic pressures that can be broken for various reasons and lead to excessive accumulation in the area.

The most common symptom is dyspnea, which is usually aggravated by exertion, although the effusion can present with a wide variety of symptoms depending on the underlying disease. In the physical evaluation, a decrease in breath sounds is frequently perceived, and among the most frequent diagnostic methods are radiography and thoracentesis. The latter is also used as a fluid drainage treatment in the most severe cases. Likewise, the administration of antibiotics is common when there is an underlying infectious cause. Treatment can be followed by respiratory rehabilitation, often through respiratory physiotherapy exercises.

Pathophysiology

Under anatomical and physiological conditions, there is a small amount of pleural fluid of no more than 10-15 ml in each hemithorax, which lubricates and facilitates the movement of the two pleural sheets that delimit the pleural cavity. There is a physiological transfer of fluid that leaks, but when there is an imbalance between formation and reabsorption, pleural effusion occurs. Both the visceral and the parietal pleural have a blood supply dependent on the systemic circulation, but differ in venous return. The capillaries of the visceral pleura drain into the pulmonary veins while those of the parietal drain into the vena cava.

Epidemiology

Pleural effusion is the most common disease of the pleural cavity with an annual incidence of 0.4% in industrialized countries. A large-scale observational study published in 2020 found a prevalence of 7.7% in patients admitted to hospitals. Intensive care unit (ICU), another published the same year placed it at 25.5% of patients admitted to this unit.

The annual incidence in Germany is estimated to be between 400,000 and 500,000 cases per year.

Causes

The liquid can have two different origins, it can be the result of an exudate or a transudate.

Transudate occurs in cases of congestive heart failure (CHF) in 40-72%, while exudate is more common in parapneumonic symptoms (50-70%), neoplasms (42-60%) and tuberculosis (23.5%).

Hydrothorax (transudates)

They occur mainly in CHF heart failure, 80% are bilateral effusions. Other causes are liver cirrhosis, chronic renal failure, nephrotic syndrome, peritoneal dialysis.

Hydrothorax fluid has a neutral pH, is characterized by lower density and lower protein concentration < 3gr/dl), while LDH increases.

Transudative and exudative effusions of the pleura are differentiated by comparing the biochemistry of the pleural fluid from that of the blood. According to the meta-analysis, such pleural exudative effusions need at least one of the following criteria:

1. Protein in pleural fluid 2,9 g/dL (29 g/L)
2. Cholesterol in pleural fluid 45 mg/dL (1.16 mmol/L)
3. LDH in pleural fluid 60 % of the upper limit of serum

Your clinic will depend to a large extent on the underlying disease. They usually present with dyspnea, orthopnea, nocturia, and malleolar edema. Its most characteristic signs are fluid dullness to percussion and a decrease in both vesicular murmur and vocal vibrations.

Exudates

The causes that produce the exudate can have different origins:

• Pulmonary: carcinoma, inflammation, lymphoma, metastasis, infarction, trauma, pneumonia, pulmonary embolism, empyema, tuberculosis, virus infections, fungi, rickettsia or parasites and connective tissue diseases

• Extrapulmonary: idiopathic, cirrhosis, LES, pancreatitis, subfrenic abscess, pregnancy, uremia, exposure to asbestos, Meigs syndrome, quilothorax, sarcoidosis, reaction to drugs and post-infarction of myocardio

In his clinic, pain, cough, dyspnea, cyanosis, fever, and arrhythmias predominate. Its signs are similar to those of hydrothorax, decreased vocal vibrations and breath sounds, and dullness.

Signs and symptoms

Patients with a pleural effusion may not have symptoms. The most common symptom is dyspnea, which is usually aggravated by exertion, depending on the size and location of the area affected by the spill. Although this symptom is the most representative of the presence of effusion, the correlation between the degree of dyspnea and the severity of the disease is minimal. Other symptoms are largely determined by the underlying disease causing the effusion, the most common being heart failure. In cases where there is active inflammation of the pleura (pleurisy), this can manifest with localized shooting pain and sharp that increases during breathing or coughing. When the pleural effusion develops, the pain may decrease, leading to the false idea that a recovery is taking place. Depending on the cause of the spill, symptoms such as fever, cough, or general malaise may occur.

Diagnosis

Medical history and physical examination present suggestive signs such as decreased respiratory movements on the affected side, decreased vocal vibrations, dullness to percussion, as well as decreased or absent breath sounds; and there are often symptoms related to the underlying diseases that may be causing the effusion: for example, in the case of heart failure there may be jugular vein distension or edema in the legs; in the case of occurring from liver cirrhosis, ascites may occur. Thoracentesis is also of great relevance, which allows analysis of the fluid, performing cytology, antibiograms and biochemistry. Bronchoscopy can also provide information. If the diagnosis is not conclusive, a transmural biopsy or thoracoscopy can be used, and even a thoracotomy.

Thoracentesis

It is indicated in pleural effusions of unknown etiology and with more than 1 cm to the wall. Its realization allows us to analyze the liquid:

• Biochemical parameters: proteins, LDH, albumin, pH, glucose and ADA.
• Count and formula: hematites, lymphocytes and neutrophils.
• Anaerobic and aerobic crops: in nosocomial pneumonias will appear stafilococci, negative Gram; while in the acquired will be positive Gram aerobics.
• Cytology, whose sensitivity is 40-87%.

Diagnostic Imaging

The effusion becomes visible on the x-ray when it is larger than 75 ml, it can appear free or loculated. In case of doubt, it is advisable to perform a lateral decubitus radiograph on the affected side. The pleural effusion can present atypical radiological images such as:

• Interlobar accumulation of fluid that can simulate a mass.
• Subpulmonary collection that is confused with elevated hemidiaphragm (in spills below 75 ml).
• In supina position, the subsequent distribution of the free fluid can produce a homogeneous opacity of the affection hemithorax that could be mistakenly attributed to a pulmonary parenchymatous disease.
• The image of chest X-ray in pleural effusion is usually characteristic of 200 ml pleural fluid (LP) produces deletion of cardiophrenic and costdiaphragmatic angles. 50 to 75 ml of LP produce deletion of the posterior cost-diaphragmatic angle in the lateral x-ray, observing the so-called “minisco sign”. The sensitivity of chest X-ray to detect DP is 24-100% with specificity 85-100% and the sensitivity to detection of DP by utrasonide is 93% with specificity 96%.

In some cases, chest ultrasound can provide more information, its greatest utility being the detection of subpulmonary and subphrenic abnormalities. It is also used to guide thoracentesis in small or loculated effusions. However, it is not practical to recommend this examination to all patients.

CT will be used if there is associated lung pathology or when it is necessary to better define the anterior or posterior location of the process. It will also be useful in differentiating a pleural lesion from a lesion in the lung parenchyma.

In cases of massive effusion, the mediastinum may be pushed by the pressure exerted by the fluid, but if the mediastinum is centered, proximal bronchial obstruction should be suspected. Diagnostic imaging techniques help determine this displacement.

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  Masive left pleural stroke (white area) in a patient with lung cancer.

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  TAC chest CT with left pleural stroke.

• Lung expansion in a pleural spill area seen by ultrasounds

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  Microscopy of pleural fluid cytology in a mesothelioma.

Treatment

Treatment should address the causative disease and the stroke itself. The transudate generally responds to treatment of the underlying cause, and therapeutic thoracentesis is only indicated when there is a massive effusion causing severe dyspnea.

Cases of pleural effusion caused by malignancy should be treated with chemotherapy or radiation therapy. Chemical pleurodesis may be attempted by installing some compounds within the pleural space to produce a space-obliterating fibrous reaction in select patients who have persistent malignant effusion despite chemotherapy or radiation therapy.

Uncomplicated parapneumonic effusion usually responds to systemic antibiotic therapy. In complicated cases, drainage through a thoracostomy tube is required in cases of empyema, when fluid glucose is less than 40 mg/dL or pH is less than 7.2.

Most hemothoraces are drained with a chest seal. A thoracotomy is required when bleeding cannot be controlled, to remove a quantity of clots, or to treat other complications of chest trauma. On the contrary, small and stable hemothoraces can be resolved conservatively.