171 Pleural Effusion

Clinical Presentation

40-year-old man with liver failure, ascites, and absent right-sided breath sounds

Radiologic Findings

PA (Fig. 171.1A) and lateral (Fig. 171.1B) chest radiographs show complete “white-out” of the right hemithorax. No air bronchograms are seen and only the left diaphragm is perceptible on the lateral exam. Note the contralateral displacement of the tracheal air column and mediastinum “away” from the white-out on the PA exam (Fig. 171.1A).

Diagnosis

Massive Unilateral Pleural Effusion; Hepatic Hydrothorax

Differential Diagnosis

• Unilateral Opaque Thorax (“White-out”) is quite broad (Table 171.1)

• Differential can be narrowed based on location of trachea (Table 171.2)

• Other Causes of Unilateral Pleural Effusion (Table 171.3)

Fig. 171.1

Table 171.1 Unilateral Opaque Thorax (‘White-out”)

Pleural Disease	Pulmonary Disease	Chest Wall Deformity
Pleural effusion	Total lung collapse	Significant scoliosis
Pleural thickening	Pneumonia	Severe congenital or acquired chest wall deformity
Fibrothorax	Pneumonectomy	Large chest wall hematoma
Diffuse malignant mesothelioma	Pulmonary agenesis	Large chest wall tumor
Metastatic pleural cancer		Diaphragmatic hernia

Table 171.2 Unilateral Opaque Thorax (“White-out”) Based on Trachea Location

Pulled “Toward” White-Out	Pushed “Away” from White-out	Central Position
Total lung collapse	Pleural effusion	Pleural thickening
Pneumonectomy	Diaphragmatic hernia	Fibrothorax
Pulmonary agenesis	Severe congenital or acquired chest wall deformity	Diffuse malignant mesothelioma
		Metastatic pleural cancer
		Large chest wall hematoma
		Large chest wall tumor

Table 171.3 Unilateral Pleural Effusion Differential Diagnosis

Heart failure

Parapneumonic-empyema

Neoplasia

Pulmonary thromboembolism

Autoimmune-collagen vascular disorders

Trauma

Chylothorax

Subdiaphragmatic diseases and disorders

Discussion

Background

Pleural effusion is an abnormal accumulation of fluid in the pleural space and a common manifestation of local and systemic diseases that involve the thorax, affecting an estimated 1.3 million persons each year. The normal pleural cavity contains a small volume of fluid (5–15 mL) that provides a frictionless surface between the visceral and parietal pleura as lung volume changes during respiration. However, between 1 and 2.5 L of pleural fluid is produced each day. Pleural fluid normally forms and flows from capillaries in the parietal pleura into the pleural space and is absorbed through parietal pleural lymphatics. The parietal pleura vasculature drains to the right side of the heart, whereas the visceral pleura vasculature drains to its left side. The formation and absorption of pleural fluid is governed by Starling’s equation. That is, the net filtration and resorption of water and its solutes (i.e., pleural fluid) across a semi-permeable membrane (i.e., pleura) are determined by balances between hydrostatic and osmotic pressures. Anything that upsets this balance results in accumulation of pleural fluid: (1) increased hydrostatic pressure (e.g., heart failure, constrictive pericarditis); (2) decreased osmotic pressure (e.g., cirrhosis, hypoalbuminemia); (3) decreased pleural space pressure (e.g., atelectasis); (4) increased microvasculature permeability (e.g., neoplasia, inflammatory conditions); (5) impaired lymphatic drainage (e.g., neoplasia, fibrosis, radiation therapy); and (6) increased transportation of fluid from the peritoneal space into the pleural space (e.g., ascites, nephrotic syndrome).