Pleural diseases

Question 1

Functions of the pleura

Answer 1

• Having 2 pleural layers decreases friction during breathing and allows for less work required
• Parietal pleura capillaries form pleural fluid due to hydrostatic pressure slightly exceeding oncotic pressure (also lymphatic drainage factors)
• Pleural fluid is reabsorbed by parietal pleura
• Diseases that deviate mediastinum toward side of lesion: atelectasis, pleural fibrosis
• Diseases that deviate mediastinum away from side of lesion: pneumothorax, pleural effusion, large mass

Question 2

Pleural effusion

Answer 2

• Any amount of pleural fluid that is radiographically or clinically detectable
• Mechanisms: decreased oncotic pressure (hypoalbuminemia), increased venous (hydrostatic) pressures (CHF), obstruction of lymphatic drainage (these are transudative except lymph obstruction)
• The most common cause of pleural effusion is increased capillary permeability (exudative)

Question 3

Special types of exudative pleural effusions

Answer 3

• Hemothorax: blood in the pleural space usually after trauma, hematocrit in the fluid is >50%
• Hemhorrhagic: same as hemothroax but hematocrit is <50% (etiology is usually tumor or TB)
• Chylous pleural effusion: develops after obstruction of lymphatics, usually associated w/ tumors, fluid contains fait
• Empyema: pus in the pleural, due to infection
• Parapneumonic effusion: developed due to pneumonia, but w/o direct infection of the pleura
• Loculated pleural effusion: fluid in localized areas of the pleural (scarred areas), w/o any free fluid (looks like a mass)

Question 4

Signs and Sx of pleural effusion

Answer 4

• Sx: chest pain (pleuritic= worse on inspiration), aching discomfort dyspnea, cough, sputum production, fever, weight loss
• Signs: decreased breath sounds, dullness to percussion, decreased movement, tachypnea

Question 5

Radiologic findings and Dx of pleural diseases

Answer 5

• On CXR can see blunted costal diaphragmatic angle, air fluid line
• Do thoracentesis to Dx what type of pleural effusion
• Protein and LDH amount separates exudates from transudates
• Check for decreased glc (infection, CA), cytology (CA), absolute cell count
• Culture
• Fluid is exudative if two of the following are met: protein ratio >.5, LDH ratio >.6, absolute LDH amount is > 2/3 upper limit of normal serum LDH
• One way to confirm it is transudative: absolute difference btwn pleural and serum albumin is ≥1.2 (smaller difference indicates exudate)

Question 6

Causes of transudative effusions

Answer 6

• Altered mechanical pressures: CHF, SVC obstruction, atelectasis
• Low oncotic pressures (nephrotic syndrome, hypoalbuminemia)
• Connection w/ transudative peritoneal fluid (peritoneal dialysis)

Question 7

Causes of exudative effusions

Answer 7

• > 50% of them are due to malignancies either lung or breast tumors
• These arise either from pleural seeding or lymphatic drainage impairment
• The effusions that show high metabolism (low pH, low glc) have poorer prognoses
• Other causes: infection, CTD, pancreatitis, chylothorax, hemothorax
• Biopsies done to distinguish btwn various forms of exudative