Pathophysiology of pleural effusions Flashcards
Histology of visceral pleura
primarily CT
contributes to elastic recoil
Histology of parietal pleura
thin layer of loose CT
BV + lymphatic lacunae
covered by a thin layer of mesothelial cells
produces/absorbs fluid
Lymphatic stoma
exists only within the parietal pleura
removes fluid
Normal pleural fluid
about 8 ml/ side
pH 7.6
Pressure gradient across pleura
oncotic pressures balanced
hydrostatic pressure +6 cm H2O towards visceral pleura
Causes of increased pleural fluid entry
increase in permeability (exudate)
increased microvasculature pressure
decreased pleural pressure (atelectasis)
decreased plasma oncotic pressure (low protein)
Causes of increased pleural fluid entry from other organs
Hepatic hydrothorax Urinothorax Chylothorax (from thoracic duct) CSF esophagus pancreas
Decreased fluid exit
impaired lymphatic drainage
Clinical features of pleural effusion
SOB
Pleuritic chest pain
asymptomatic
Percussion dull, decreased tactile fremitus
auscultation decreased air entry
Imaging of pleural effusion
US: close to 100% sensitive
CT with contrast: pleural surface - thickening, tumours etc
not indicated in every case
Tx for pleural effusion
Thoracentesis
Pleural fluid analysis
Colour (Frank blood - >50% hematocrit, hemothorax) Smell Chemistry - protein, LDH, albumin WBC-D Cytology - cancer pH, glucose gram stains + cultures
> 85% lymphocytes: TB, cancer, rheumatoid
10% eosinophils: pneumo/hemothorax
neutrophils - infections
Light’s criteria
Transutae vs exudate pleural fluid (85% sensitive for exudate)
fluid protein/serum protein >0.5
fluid LDH/serum LDH>0.6
fluid LDH > 2/3 upper limit of normal
Transudate pleural effusion
low protein and LDH in pleural fluid
intact endothelial membrane
increased hydrostatic pressure or decreased oncotic pressure
Exudate
high protein and LDH in pleural fluid
disruption of endothelial membrane
DDx of transudate pleural effusion
LUCKI ME Liver Urinothorax CHF Kidney Iatrogenic Myxedema Embolic
DDx of exudate
everything other than transudate malignancy infection PE serositis due to CT damage
Incidence of pleural effusion (causes)
CHF 37.6%
pneumonia 48% non-cardiac effusions
cancer - 24%
Parapneumonic effusion
fluid formation - inflammation/infection of fluid
uncomplicated effusion (exudate)
complicated - pH < 7.2
empyema
Empyema
Infection of pleural space leading to fibrous peel around the lung
severe sepsis
Chest tube drainage if complicated (low pH)/empyema
if cannot drain properly, may need surgical decortication
Malignant effusion
Primary: mesothelioma (cancer of pleura, secondary to asbestosis)
Metastatic - much more common
Pathophysiology of malignant effusion
Direct - hematogenous spread, obstruction of lymphatic drainage Indirect - Hypoproteinemia Post-obstructive pneumonitis Treatment related PE thoracic duct obstruction pericardial involvement
