Symptom-Based Approach: Pleural Effusion

“Why is this patient breathless?” — Think beyond the lungs. Think fluid. Think strategy.

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🧩 Clinical Vignette

A 68-year-old man presents with progressive shortness of breath over 2 weeks. He has a history of congestive heart failure and was recently hospitalized for pneumonia. On exam, decreased breath sounds and dullness to percussion are noted over the right lower chest.

How do we approach a case like this?
Let’s break it down step by step — clinical reasoning, red flags, useful questions, and imaging clues.

🔍 Step 1: Think Anatomically

Pleural effusion = fluid in the pleural space. Causes broadly fall into:

• 🫀 Transudative: imbalance in hydrostatic/oncotic pressure (e.g., CHF, nephrotic syndrome)
• 🧫 Exudative: inflammation or infection (e.g., pneumonia, TB, malignancy)

Always ask yourself:
Is this a passive leak or an active process?

🚩 Red Flags in Pleural Effusion

These features require urgent evaluation:

Red Flag	Why It Matters
Fever + pleural effusion	→ Empyema, TB — needs drainage, not just antibiotics
Massive unilateral effusion	→ Consider malignancy, especially in smokers
Weight loss, night sweats	→ TB or cancer until proven otherwise
Hypotension, tachycardia	→ Possible tension physiology (rare but fatal)
Trauma history	→ Hemothorax, diaphragmatic injury
Sudden dyspnea + chest pain	→ Pulmonary embolism with hemorrhagic effusion

🗣️ Useful English Expressions

Doctor:

• “Have you noticed any swelling in your legs?”
• “Do you feel more short of breath when lying flat?”
• “Have you been coughing up anything unusual?”

Patient:

• “It’s hard to breathe, especially when I’m lying down.”
• “I get tired just walking to the bathroom.”
• “I lost some weight recently, but I didn’t try to.”

🩺 Physical Examination Highlights

Finding	What it suggests
↓ Tactile fremitus	Fluid dampens vibration
↓ Breath sounds	Classic in large effusions
Dullness to percussion	Dense fluid replaces air
Egophony at the top of the effusion	“E to A” change = compressed lung above the fluid
Tracheal deviation (if massive)	Shift away from the fluid

🩻 Barrel chest? Not in effusion — think COPD/emphysema.

📚 USMLE-Style “One-Liner Diagnoses”

• CHF + bilateral effusions + orthopnea → Transudate (Light’s criteria)
• Post-MI + fever + pleuritis → Dressler syndrome
• Weight loss + massive right effusion → Lung cancer
• Fever + recent pneumonia → Parapneumonic effusion or empyema
• HIV + lymphocytic exudate + night sweats → TB

🧪 Initial Workup

• CXR: Blunting of costophrenic angles
• Ultrasound: Confirms fluid, guides thoracentesis
• Thoracentesis: Check protein, LDH (Light’s Criteria), cell count, cytology, glucose
• CT Chest (if malignancy suspected)

🧠 Clinical Reflection

Pleural effusion is not a diagnosis — it’s a clue. Your job is to decode its message.

Is it passive, like CHF? Is it active, like TB, malignancy, or infection?

Don’t forget post-surgical causes, autoimmune conditions, or drug reactions. Always integrate imaging, fluid analysis, and history — never rely on one alone.

📌 Clinical Pearls

• Egophony above the fluid level = compressed lung, not effusion itself
• Empyema = low pH, low glucose, high LDH → needs drainage
• TB pleuritis = high lymphocytes, elevated ADA
• Malignancy = cytology positive in ~60%, often recurrent
• Don’t tap every effusion — if bilateral + clear CHF picture, diuretics may suffice

📘 Take-Home Messages

• Use Light’s criteria to classify effusions
• Tactile fremitus ↓, percussion dull, breath sounds ↓ = classic triad
• POCUS is your friend — fast, safe, bedside
• Always think cancer or TB in subacute, unexplained effusions
• If effusion recurs despite treatment, consider biopsy or pleuroscopy

🔗 Related Learning

• 🗾 Read in Japanese here
• ▶ Clinical Reasoning Guide: How to Approach Unknown Cases
• 🏠 Back to Symptom-Based Approach Home

🩺 Looking for real-world practice? Check out our Mock Patient Script on Pleural Effusion featuring 4 diverse cases including malignancy, SLE, chylothorax, and CHF. Ideal for OSCE or USMLE Step 2 CS preparation.