What are the causes of transudative pleural effusion?

From the Guidelines

Transudative pleural effusions are primarily caused by conditions such as congestive heart failure, cirrhosis, nephrotic syndrome, and hypoalbuminemia, which alter the balance of hydrostatic and oncotic pressures in the pleural space. These conditions, as noted in the European Respiratory Journal study 1, account for more than 80% of transudates, with heart failure being the most common cause, followed by liver cirrhosis. The pathophysiology involves an imbalance in the forces that regulate fluid movement in and out of the pleural space, leading to fluid accumulation without significant inflammation or protein leakage characteristic of exudative effusions.

Common Causes of Transudative Pleural Effusions

• Congestive heart failure: Increases hydrostatic pressure in the pulmonary circulation, leading to fluid leakage into the pleural space 1.
• Cirrhosis with ascites: Decreased albumin production reduces oncotic pressure, and portal hypertension promotes fluid movement into the pleural space.
• Nephrotic syndrome: Lowers serum albumin levels and oncotic pressure, leading to fluid accumulation.
• Hypoalbuminemia: From various causes like malnutrition or protein-losing enteropathy, reduces oncotic pressure and leads to fluid leakage into the pleural space.

Diagnosis and Management

Diagnosis of transudative pleural effusions typically involves thoracentesis with fluid analysis, showing protein and LDH levels below the exudative criteria thresholds 1. Management often focuses on treating the underlying cause, such as the use of diuretics for heart failure, which can successfully treat most transudates and make further investigations unnecessary, as highlighted in the British Thoracic Society guideline for pleural disease 1.

Clinical Approach

A systematic approach to investigation, starting with a careful history and physical examination, is crucial for establishing a diagnosis swiftly and minimizing unnecessary invasive investigations 1. The use of thoracic ultrasound (TUS) as an initial diagnostic tool and to guide invasive procedures is also emphasized in the British Thoracic Society guideline 1.

From the Research

Transudative Pleural Effusion Causes

• Congestive heart failure is the most common cause of transudative pleural effusion, as stated in the study 2
• Other common causes include:
  • Pulmonary embolism 2
  • Cirrhosis of the liver with ascites 2
  • Nephrotic syndrome 2
• The diagnosis of transudative effusion is established by examining the characteristics of the pleural fluid, which include:
  • A ratio of pleural fluid to serum protein of less than 0.5 2
  • A ratio of pleural fluid to serum LDH of less than 0.6 2
  • A pleural fluid LDH of less than two thirds the upper limit of normal for the serum LDH 2
• Management of transudative pleural effusions involves managing the primary disease, as mentioned in the studies 2, 3, and 4
• Refractory, massive effusions can be controlled by tetracycline pleurodesis, as stated in the study 2
• In some cases, therapeutic thoracentesis, pleurodesis with talc, or insertion of an indwelling pleural catheter may be necessary, as mentioned in the study 4