STEPTRACKERRESPIRATORY | PATHOLOGY + PHYSIOLOGY | HIGH-YIELD REVIEW

Pleural Disease

Fluid, air or tumor in the pleural space — transudate vs exudate, spontaneous vs tension pneumothorax, and mesothelioma.

FOCUS ON

Use Light's criteria to separate transudates (pressure problems: HF, cirrhosis, nephrotic) from exudates (leaky or blocked: infection, cancer, TB). Tension pneumothorax: trachea shifts away, hypotension → needle decompression now. Mesothelioma: asbestos, calretinin/WT-1 ⁺, long microvilli.

CONDITION

MECHANISM · CAUSES

FINDINGS

CLUE · TREATMENT

Transudative effusion

↑ hydrostatic or ↓ oncotic pressure: heart failure (most common), cirrhosis, nephrotic syndrome, hypoalbuminemia

Low protein and LDH; often bilateral

Treat the underlying condition

Exudative effusion

↑ capillary permeability or lymphatic blockage: pneumonia, malignancy, TB, PE, pancreatitis, RA, SLE

Light's: pleural/serum protein > 0.5, LDH ratio > 0.6, or pleural LDH > ⅔ normal upper limit

RA effusion: very low glucose

Empyema

Infected parapneumonic fluid

Pus; pH < 7.2, low glucose

Chest tube drainage

Chylothorax

Thoracic duct injury (surgery, trauma) or obstruction (lymphoma)

Milky fluid; triglycerides > 110 mg/dL

After esophagectomy or cardiac surgery

Primary spontaneous pneumothorax

Rupture of an apical subpleural bleb

Sudden unilateral pleuritic pain, dyspnea; ↓ breath sounds, hyperresonance

Tall, thin young men; smokers; Marfan

Secondary pneumothorax

Underlying lung disease: COPD bullae, CF, Pneumocystis, LAM, catamenial (endometriosis)

Worse tolerated (poor reserve)

Recurs with menses → catamenial

Tension pneumothorax

One-way valve (trauma, ventilation) traps air with each breath

Trachea and mediastinum shift away; hypotension, JVD, absent breath sounds

Needle decompression, then chest tube

Malignant mesothelioma

Asbestos (decades of latency); smoking does not add risk

Pleural rind encasing the lung, recurrent hemorrhagic effusion, chest pain; psammoma bodies

Keratin, calretinin, WT-1, D2-40 ⁺; CEA⁻, TTF-1⁻; long slender microvilli on EM

Pleural plaques

Asbestos exposure marker

Calcified plaques on parietal pleura and diaphragm

Benign — not mesothelioma

Mechanism — fluid and air in the pleural space

Starling forcesHydrostatic vs oncotic

→

ImbalanceTransudate

Leaky or blockedExudate

Air enters pleura

→

Negative pressure lostLung recoils, collapses

→

One-way valvePressure ↑ → venous return ↓ → shock

Reading pleural fluid

FLUID / TEST

FINDING

THINK

Light's criteria

Any positive

Exudate

pH < 7.2, pus

Infection

Empyema — drain

Very low glucose

< 30 mg/dL

RA, empyema, TB, cancer

Triglycerides > 110

Milky

Chylothorax

High amylase

—

Pancreatitis, esophageal rupture

Bloody

—

Malignancy, PE, trauma

How it's tested

COMMON CONFUSIONPleural mesothelioma and metastatic adenocarcinoma look alike. Mesothelioma is calretinin/WT-1 ⁺; adenocarcinoma is CEA/TTF-1 ⁺.

THE TRAPA hypotensive trauma patient with absent breath sounds and a deviated trachea needs needle decompression before any imaging.

YOUR APPROACHEffusion → Light's criteria → special tests (pH, glucose, TG, amylase, cytology). Pneumothorax → who (bleb, lung disease) → is it tension?

If you see… think…

HF patient, bilateral effusions, Light's negative → transudate

Pleural/serum protein ratio 0.7 → exudate

RA patient with effusion glucose 15 → rheumatoid effusion

Milky fluid after thoracic surgery → chylothorax

Purulent fluid with pH 7.0 → empyema — chest tube

Tall, thin young man, sudden pleuritic pain, hyperresonance → spontaneous pneumothorax

Stab wound, hypotension, JVD, trachea pushed away → tension pneumothorax

Shipyard worker decades later, pleural rind, bloody effusion → mesothelioma

Long slender microvilli on EM of a pleural tumor → mesothelioma

Pneumothorax recurring with periods → catamenial (endometriosis)