What is the significance and cause of left hilar fullness on a radiograph, particularly in a patient with a history of smoking or respiratory symptoms?

Left Hilar Fullness: Radiographic Significance and Causes

Left hilar fullness on chest radiography represents enlargement or increased density of the left hilum that warrants further evaluation with CT imaging to distinguish between vascular, lymphatic, infectious, and neoplastic etiologies.

What Left Hilar Fullness Means

Left hilar fullness indicates abnormal prominence of structures at the left pulmonary hilum, which normally consists of the left pulmonary artery, left descending pulmonary artery, and left superior pulmonary vein 1. The left hilum is anatomically complex and poorly visualized on conventional chest radiography, making interpretation challenging 2, 3.

The finding is nonspecific and requires correlation with clinical context and advanced imaging to determine the underlying cause 2, 3.

Primary Causes to Consider

Malignant Causes

• Lung cancer is the most concerning etiology, particularly in patients with smoking history 4, 5
• The most common sites of intrathoracic spread in lung cancer are hilar and mediastinal lymph nodes, with bulky hilar adenopathy causing extrinsic airway compression 4
• Lymphoma can present as hilar masses with associated mediastinal adenopathy 3
• Approximately 25% of lung cancer patients are asymptomatic at diagnosis, but the majority present with symptoms including cough, dyspnea, chest pain, or hemoptysis 4

Infectious/Inflammatory Causes

• Tuberculosis can present as a hilar mass mimicking malignancy, with perihilar consolidation and mediastinal lymphadenopathy 6
• Sarcoidosis uncommonly presents as unilateral hilar tumor mass, though bilateral hilar adenopathy is more typical 5
• Both conditions show noncaseating granulomas on biopsy and can demonstrate high metabolic activity on PET-CT 6, 5

Vascular Causes

• Pulmonary hypertension causes enlargement of the left descending pulmonary artery with associated pruning of peripheral vessels 7
• Aortic pseudoaneurysm can present as a left hilar mass, particularly with posterior location and lack of contralateral hilar adenopathy 3
• Vascular masses are readily defined by CT with contrast 3

Critical Clinical Features to Assess

High-Risk Patient Characteristics

• Smoking history (particularly >20 pack-years) significantly increases risk of lung cancer and warrants aggressive workup 4
• Recurrent pneumonia in the same anatomic distribution or relapsing COPD exacerbations should raise concern for endobronchial obstruction from neoplasm 4
• Persistent hemoptysis, even in scant amounts, in smokers with COPD suggests possible endobronchial tumor 4

Symptoms Suggesting Intrathoracic Spread

• Hoarseness indicates possible recurrent laryngeal nerve involvement (more common on left due to nerve's circuitous route under the aortic arch) 4
• Dysphagia suggests subcarinal adenopathy compressing the mid-esophagus 4
• Localized chest pain may indicate pleural or chest wall invasion 4

Diagnostic Algorithm

Initial Imaging Approach

Chest radiography is appropriate for initial screening but has significant limitations 4:

• Sensitivity for detecting pulmonary nodules is only 28% compared to CT 8, 9
• Cannot reliably distinguish between benign and malignant causes 2, 3

Definitive Imaging

CT chest with IV contrast is the gold standard for evaluating left hilar fullness 8, 9, 3:

• Contrast improves detection of mediastinal and hilar adenopathy by distinguishing nodes from mediastinal vessels 4, 9
• Provides superior spatial localization for detecting small pulmonary nodules 4, 8
• Readily defines vascular hilar masses (aneurysms, pulmonary hypertension) 7, 3
• Aids in delineating soft tissue extension of skeletal metastatic disease 4, 9

CT without contrast is acceptable if the primary concern is pulmonary nodules alone, but contrast should be added when evaluating hilar fullness to assess lymphadenopathy 8, 9.

Tissue Diagnosis

When malignancy or lymphoma are suspected 3:

• Endobronchial ultrasound-guided needle aspiration (EBUS-NA) for accessible hilar/mediastinal nodes 4
• Mediastinoscopy with lymph node biopsy when EBUS is non-diagnostic 5
• Bronchoscopy with endobronchial biopsy for visible mucosal abnormalities 6
• Target the most advanced site of disease first for efficient staging 4

Critical Pitfalls to Avoid

• Never rely on chest radiography alone when hilar fullness is identified—sensitivity is inadequate and up to 72% of lesions may be missed 8, 9
• Do not assume malignancy without histological confirmation—benign conditions like sarcoidosis and tuberculosis can present as hilar masses with high PET-CT uptake 6, 5
• Avoid ordering CT without and with contrast (dual-phase)—there is no supporting literature for this approach in hilar mass evaluation 8, 9
• Do not dismiss symptoms in smokers—recurrent pneumonia in the same location, persistent hemoptysis, or hoarseness warrant immediate advanced imaging regardless of radiographic findings 4
• Consider vascular causes when the mass has posterior location without contralateral adenopathy—CT with contrast will prevent dangerous biopsy attempts on vascular structures 3