Causes of Pleural Effusions
Among the options provided, congestive heart failure and breast cancer are established causes of pleural effusions, while dehydration, allergies, and bronchiectasis are not recognized as primary causes.
Confirmed Causes from the Options
Congestive Heart Failure
- Heart failure is the most common cause of pleural effusions, accounting for 29% of all cases and more than 80% of transudative effusions 1, 2.
- Fluid overload from cardiac impairment creates hydrostatic imbalances that drive pleural fluid accumulation 3.
- Heart failure represents the leading etiology in hospitalized patients, with modern studies differentiating true heart failure (9.6%) from pure fluid overload (61.5%) 3.
Breast Cancer
- Breast cancer is the second most common malignancy causing pleural effusions after lung cancer 1.
- Malignancy overall accounts for 26% of all pleural effusions, with breast cancer being a major contributor to this category 1, 4.
- Malignant effusions from breast cancer are exudative and often recurrent with poor prognosis 5.
Non-Causes from the Options
Dehydration
- Dehydration does not cause pleural effusions; it would theoretically reduce fluid accumulation rather than increase it.
- The pathophysiology of effusions requires either increased hydrostatic pressure, decreased oncotic pressure, increased capillary permeability, or impaired lymphatic drainage—none of which occur with dehydration 1.
Allergies
- Allergies are not recognized as a cause of pleural effusions in any major guideline or clinical series 1, 4.
- While eosinophilic pleural effusions exist, they are typically related to parasitic infections, drug reactions, or malignancy—not simple allergic responses 3.
Bronchiectasis
- Bronchiectasis is not a primary cause of pleural effusions 3.
- While chronic suppurative lung conditions like bronchiectasis may occasionally produce small effusions, this is rare and not considered a standard etiology 3.
- The guideline mentions bronchiectasis only in the context of pediatric infections where it may be associated with effusions, but not as a direct cause 3.
Additional Common Causes (Not Listed in Options)
For clinical context, the most common causes of pleural effusions include:
- Pneumonia (16% of cases): Parapneumonic effusions are the most common exudative cause 1, 4, 5.
- Tuberculosis (6% of cases): Important exudative cause, especially in endemic regions 1, 4.
- Pulmonary embolism: Associated with effusions in up to 40% of cases, with 80% being exudates 2.
- Cirrhosis (3% of cases): Accounts for approximately 10% of transudates 1, 2.
- End-stage renal failure: Prevalence of 24.7% among ESRF patients due to fluid overload, heart failure, and uremic pleuritis 3, 1, 2.
Clinical Pitfall
Do not assume all effusions in heart failure patients are cardiac in origin—malignancy, infection, and pulmonary embolism must be reconsidered in persistent or atypical cases, as they are amenable to specific treatment 1, 2.