---

---

***LISTEN TO THE PODCAST HERE***

---

---

Pleural Anatomy and Physiology

• 2 types of pleura in the thorax
  • Parietal pleura
    • Which covers the chest wall and diaphragm
    • 30-40 micrometers thick
    • Contains lymphatic stomata
      • Holes between the mesothelial and subpleural layers that allow for drainage into the lymphatic system
    • Contains intercostal microvessels
      • Produce interpleural fluid
  • Visceral pleura
    • Which covers the lung parenchyma
    • 20-80 micrometers thick
    • Contain bronchial microvessels
      • Arise from pulmonary veins and produce interpleural fluid

• The interpleural space is between them and produces 0.1-0.2 mL/kg (10-20 mL per hemithorax) of fluid to keep these pleura from adhering to each other and maintain lubrication
  • This fluid is constantly produced (0.01 mL/kg/hr) and absorbed
  • Originates from the systemic pleural microvessels
    • Theorized that parietal is more important
      • Intercostal microvessels are closer to the interpleural space
      • Higher filtration pressure than pulmonary veins
  • Dependent on balance of hydrostatic pressure opposed by the counterbalancing osmotic pressure and membrane permeability
    • Transudative fluid collection
      • Increased hydrostatic pressure
      • Decreased oncotic pressure
    • Exudative fluid collection
      • Decreased pleural membrane permeability
      • Lymphatic blockage

---

Associated Diseases and Causes

---

Clinical Presentation

• Symptoms      
  • Patients can be asymptomatic, have fluid specific symptoms, and have disease specific symptoms
  • Fluid specific
    • Dyspnea
    • Cough
    • Pleuritic chest pain
  • Disease specific
    • Fever, hemoptysis, orthopnea, peripheral edema, weight changes, ascites
• Physical Examination
  • Fluid specific
    • Decreased or asymmetric chest wall movement
    • Decreased breath sounds
    • Dullness to percussion
    • Decreased tactile fremitus
    • Pleural friction rub
    • (+) egophony
  • Disease specific
    • Crackles, JVD, hepatosplenomegaly, lymphadenopathy, S3 gallop, pitting edema,

---

Imaging in Suspected Pleural Effusions

• Chest Radiograph
  • Blunting of the costophrenic angle
    • At least 150mL needed on PA
    • At least 50mL needed on lateral decubitus
  • At least 500mL needed for diaphragm obliteration

• Computed Tomography
  • Can detect as little as 2mL of fluid

• Ultrasound
  • Can detect as little as 20mL
  • Phased array probe with patient sitting upright
  • Scan posterior/lateral caudal to cranial to find fluid line
  • (+) spine sign

---

Thoracentesis

• Once the diagnosis is made, a thoracentesis needs to be performed for biochemical fluid analysis

---

Fluid Analysis

• Routine fluid labs
  • Cell count and differential
  • pH
  • Protein
  • LDH
  • Glucose
  • Cholesterol
• Non-routine
  • N-terminal BNP
  • Triglycerides
  • Creatinine
  • Amylase
  • Cancer-related biomarkers
• Lights Criteria
  •  Exudative if one (1) of following present:
    • Pleural/serum protein ratio > 0.5
    • Pleural/serum LDH > 0.6
    • Pleural fluid LDH > 2/3^rd ULN of serum LDH
  • Lights Criteria Criticism
    • Needs both pleural fluid and serum
    • Newer studies use only pleural fluid
      • Exudative if one (1) of the following:
        • Pleural fluid cholesterol > 45 mg/dL
        • Pleural fluid protein > 2.6 g/dL
        • Pleural fluid LDH > 0.45x ULN of serum LDH

---

Treatment

• Non-malignant effusions
  • Treat underlying condition
  • Repeated drainage for symptomatic patients
  • If persistent:
    • Repeat thoracentesis as needed
    • Revisit primary diagnosis
    • Consider pleurodesis
      • Chemical
        • Talc slurry or doxycycline through chest tube
      • Mechanical
        • VATS
    • Indwelling pleural catheter
      • Reserved for patients who decline, fail, or not candidates for pleurodesis

• Malignant effusions
  • Can be complicated

---

Cottage Physician (1898)

---

---

References

1. Lai-Fook SJ. Pleural mechanics and fluid exchange. Physiol Rev. 2004; 84(2):385-410. [pubmed]
2. Jantz MA, Antony VB. Pathophysiology of the pleura. Respiration. 2008; 75(2):121-33. [pubmed]
3. Feller-Kopman D, Light R. Pleural Disease. N Engl J Med. 2018; 378(8):740-751. [pubmed]
4. http://www.meddean.luc.edu/lumen/MedEd/medicine/pulmonar/apd/plep.htm
5. Saguil A, Wyrick K, Hallgren J. Diagnostic approach to pleural effusion. Am Fam Physician. 2014; 90(2):99-104. [pubmed]
6. Wong CL, Holroyd-Leduc J, Straus SE. Does this patient have a pleural effusion? JAMA. 2009; 301(3):309-17. [pubmed]
7. Chesnutt AN, Chesnutt MS, Prendergast NT, Prendergast TJ. Pleural Effusion. In: Papadakis MA, McPhee SJ, Rabow MW. eds. Current Medical Diagnosis and Treatment 2020. McGraw-Hill; Accessed July 05, 2020. https://accessmedicine-mhmedical-com.ezproxy.uthsc.edu/content.aspx?bookid=2683&sectionid=225058693
8. Light RW. Disorders of the Pleura. In: Jameson J, Fauci AS, Kasper DL, Hauser SL, Longo DL, Loscalzo J. eds. Harrison’s Principles of Internal Medicine, 20e. McGraw-Hill; Accessed July 05, 2020. https://accessmedicine-mhmedical-com.ezproxy.uthsc.edu/content.aspx?bookid=2129&sectionid=192031615
9. Moskowitz H, Platt RT, Schachar R, Mellins H. Roentgen visualization of minute pleural effusion. An experimental study to determine the minimum amount of pleural fluid visible on a radiograph. Radiology. 1973; 109(1):33-5. [pubmed]
10. Radiopaedia. Pleural Effusions. https://radiopaedia.org/articles/pleural-effusion?lang=us
11. Gonlugur U, Gonlugur TE. The distinction between transudates and exudates. J Biomed Sci. 2005; 12(6):985-90. [pubmed]
12. Heffner JE, Brown LK, Barbieri CA. Diagnostic value of tests that discriminate between exudative and transudative pleural effusions. Primary Study Investigators. Chest. 1997; 111(4):970-80. [pubmed]
13. Steger V, Mika U, Toomes H, et al. Who gains most? A 10-year experience with 611 thoracoscopic talc pleurodeses. Ann Thorac Surg. 2007; 83(6):1940-5. [pubmed]
14. Patil M, Dhillon SS, Attwood K, Saoud M, Alraiyes AH, Harris K. Management of Benign Pleural Effusions Using Indwelling Pleural Catheters: A Systematic Review and Meta-analysis. Chest. 2017; 151(3):626-635. [pubmed]
15. Feller-Kopman DJ, Reddy CB, DeCamp MM, et al. Management of Malignant Pleural Effusions. An Official ATS/STS/STR Clinical Practice Guideline. Am J Respir Crit Care Med. 2018; 198(7):839-849. [pubmed]
16. Bibby AC, Dorn P, Psallidas I, et al. ERS/EACTS statement on the management of malignant pleural effusions. Eur Respir J. 2018; 52(1):. [pubmed]