10 Questions
Which of the following conditions can decrease lymphatic flow?
Increased systemic venous pressure
What is the primary goal of diagnostic thoracentesis?
To identify potential causes of the pleural effusion
Which of the following is a contraindication to thoracentesis?
Severe bleeding diathesis
What is the most common indication for therapeutic thoracentesis?
Symptom relief
Which of the following is a result of mechanical compression of lymphatics?
Pleural effusion
What is the purpose of examining the pleural fluid microscopically?
To analyze the cellular content of the fluid
Which of the following is an indication for therapeutic thoracentesis?
All of the above
What is the consequence of insufficient pleural fluid for thoracentesis?
Contraindication to thoracentesis
What is the primary goal of therapeutic thoracentesis?
To provide symptom relief
Which of the following is a characteristic of a complicated pleural effusion?
Loculations
Study Notes
Pleural Effusion
- The pleura consists of two layers: parietal pleura (covers chest wall, diaphragm, and mediastinum) and visceral pleura (covers lungs, including interlobar fissures).
- The two layers are separated by a virtual cavity containing 5-10 mL of fluid.
Pleural Liquid Turnover
- Pleural liquid originates from systemic vessels of both parietal and visceral pleural membranes.
- Parietal vessels are more important due to proximity to the pleural space and higher filtration pressure.
- Pleural liquid is partially reabsorbed by microvessels, with remaining fluid exiting via lymphatic stomata in the parietal pleura.
Pathways to Pleural Effusion
- Increased fluid entry:
- Increased microvascular pressure (elevated venous pressure, CHF, pulmonary embolism, central venous obstruction)
- Increased permeability (inflammation, infection, malignancy)
- Decreased pleural pressure (atelectasis)
- Decreased plasma osmotic pressure (hypoalbuminemia)
- Decreased fluid exit:
- Intrinsic factors: cytokines, endocrine abnormalities, radiation/drug injury, cancer infiltration, anatomic abnormalities
- Extrinsic factors: limited respiratory motion, mechanical compression, decreased intrapleural pressure, increased systemic venous pressure
Determining the Cause of Pleural Effusion
- Thoracentesis with imaging guidance is a simple bedside procedure for rapid fluid sampling and analysis.
- Analysis of pleural fluid helps determine the cause of the effusion.
Indications for Thoracentesis
- Diagnostic: most patients with newly detected pleural effusion should undergo diagnostic thoracentesis to determine the nature of the effusion and identify potential causes.
- Therapeutic: performed for symptom relief, complicated pleural effusions, and pleural conditions at risk of thickening and functional impairment.
Learn about the anatomy and physiology of the pleural cavity, including the parietal and visceral pleura, and their blood supply and sensory nerve distribution. Understand the structure and function of the pleura and its importance in the respiratory system.
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