Pleural effusion in a 70-year-old — etiopathogenesis, features, differential diagnosis, approach and management

Definition and normal physiology. Pleural effusion is abnormal accumulation of fluid in the pleural space. Normally only 10–20 mL of fluid is present, produced by the parietal pleural capillaries and absorbed by parietal pleural lymphatics. Effusion results when formation exceeds absorption. About 250–500 mL is needed for blunting of the costophrenic angle on an erect chest radiograph, but as little as 50 mL is detectable on ultrasound or lateral decubitus film.

Pathogenetic mechanisms. (i) Increased hydrostatic pressure — heart failure; (ii) reduced oncotic pressure — hypoalbuminaemia, nephrotic syndrome, cirrhosis; (iii) increased capillary permeability — infection, malignancy, inflammation; (iv) impaired lymphatic drainage — malignant mediastinal node involvement; (v) movement of fluid from the peritoneum through diaphragmatic defects — hepatic hydrothorax, Meigs syndrome, pancreatitis; (vi) thoracic duct rupture — chylothorax; (vii) bleeding — haemothorax.

Causes in a 70-year-old (frequency order matters).

Clinical features. Breathlessness proportional to size and to underlying lung reserve, pleuritic chest pain (parietal pleural involvement, suggesting an exudate), and a dry cough. In the frail older patient the presentation may again be non-specific — fatigue, delirium, anorexia or reduced mobility. Signs on the affected side: reduced chest expansion, stony dull percussion note, absent or diminished breath sounds, reduced vocal resonance and tactile fremitus, with a bronchial breath sound and aegophony at the upper level; large effusions cause tracheal and mediastinal shift away from the effusion. Always seek clues to the cause — raised JVP and oedema (heart failure), clubbing and weight loss (malignancy), fever and purulent sputum (empyema), lymphadenopathy, joint disease, and evening rise of temperature with weight loss (tuberculosis).

Initial imaging. Erect PA chest radiograph — homogeneous basal opacity with a meniscus sign; a lateral film detects smaller effusions; look for mediastinal shift, a mass, cardiomegaly or a "white-out". Thoracic ultrasound is now mandatory before any pleural procedure — it detects small effusions, distinguishes fluid from consolidation and pleural thickening, identifies septations suggesting empyema or malignancy, and reduces the risk of pneumothorax and organ injury. Contrast-enhanced CT thorax (ideally before complete drainage) is required for suspected malignancy or empyema and shows nodular, circumferential or mediastinal pleural thickening > 1 cm, the "split pleura" sign of empyema, and any underlying lung lesion.

Diagnostic thoracentesis and Light's criteria. Aspirate all undiagnosed effusions under ultrasound guidance; a bilateral effusion with clear-cut heart failure may be treated first and tapped only if atypical or non-resolving. Apply Light's criteria — the fluid is an EXUDATE if any one is met: (i) pleural fluid/serum protein ratio > 0.5; (ii) pleural fluid/serum LDH ratio > 0.6; (iii) pleural fluid LDH > two-thirds of the upper limit of normal serum LDH. Light's criteria misclassify about 25% of transudates as exudates in patients already on diuretics — in that situation use a serum-to-pleural-fluid albumin gradient > 1.2 g/dL or a protein gradient > 3.1 g/dL, which indicates a transudate.

Pleural fluid analysis — what to send.

When the tap is non-diagnostic. About 20–25% of effusions remain undiagnosed after two thoracenteses. Next steps: CT-guided cutting-needle pleural biopsy of thickened pleura (high yield in malignancy and tuberculosis), or medical (local anaesthetic) thoracoscopy — the investigation of choice, with a diagnostic yield above 90% for malignancy and tuberculosis, and it allows talc poudrage in the same sitting. Blind Abrams needle biopsy retains a role for suspected tuberculosis where thoracoscopy is unavailable. Consider bronchoscopy only if there is haemoptysis or a parenchymal lesion. If all are negative and there is asbestos exposure, keep mesothelioma in mind and follow up.

Management by cause. Transudate — treat the underlying disease (diuretics and guideline-directed therapy for heart failure, albumin/diuretics for cirrhosis); repeated taps are rarely needed. Parapneumonic effusion — antibiotics alone if simple; intercostal chest drain if the fluid is purulent, pH < 7.20, glucose < 60 mg/dL, loculated, or organisms are seen. Empyema — small-bore chest drain plus prolonged antibiotics; if drainage fails, intrapleural fibrinolytic therapy with alteplase plus DNase (MIST-2 regimen) improves drainage and reduces surgical referral, with VATS decortication for failure. Tuberculous effusion — standard ATT for 6 months; therapeutic aspiration for symptoms; steroids are not routinely indicated. Therapeutic aspiration should be limited to about 1.5 litres at one sitting, stopping earlier for cough or chest discomfort, to avoid re-expansion pulmonary oedema.

Malignant pleural effusion and the geriatric approach. A malignant effusion signifies advanced disease with a median survival of about 3–12 months (worst in lung cancer, best in breast cancer and mesothelioma of epithelioid type); prognosis can be estimated by the LENT score. Management is palliative and symptom-driven: observe if asymptomatic; therapeutic aspiration for a frail patient with limited life expectancy; indwelling pleural catheter (IPC) — preferred where the lung fails to re-expand (trapped lung) or where hospital stay must be minimised; and chest drain with talc pleurodesis where the lung re-expands and durable control is wanted. In the older patient the choice is driven by performance status, life expectancy, home support and patient preference, not by the size of the effusion. Treat the underlying malignancy where appropriate and involve palliative care early.

BTS Pleural Disease Guideline 2023 (Thorax). Key changes relevant to older patients: thoracic ultrasound must be used for all pleural interventions; a contrast CT should be obtained before complete drainage where malignancy is suspected; medical thoracoscopy is the preferred investigation for an undiagnosed exudate; indwelling pleural catheters and talc pleurodesis are equally acceptable first-line options for malignant effusion, with the decision made by shared decision-making; and the RAPID score (Renal, Age, Purulence, Infection source, Dietary/albumin) is endorsed for risk-stratifying pleural infection, in which age over 70 is an adverse prognostic factor.

Intrapleural therapy and IPC strategy have matured. Following MIST-2, combined intrapleural alteplase plus DNase is established for pleural infection when drainage fails, and is increasingly used in frail patients who are unfit for surgery. For malignant effusion, the AMPLE and IPC-PLUS trials support indwelling pleural catheters with daily drainage, and talc administered through the catheter to achieve pleurodesis — an approach that reduces total hospital days, which is the outcome that matters most to an older patient with limited life expectancy.