Opaque hemithorax

Abstract

A 69-year-old male patient presented with complaints of cough and progressive dyspnea. A chest X-ray showed complete opacification of the left hemithorax (Figure 1). DISCUSSIONComplete opacification of a hemithorax on chest X-ray is termed opaque hemithorax (OH) and is a common finding in emergency room patients. Attending physicians encountering an OH should be able to make an immediate decision regarding the most appropriate approach.The differential diagnosis of an OH is primarily based on the volume of the affected hemithorax, as determined by the position of the mediastinum (the position of the trachea providing the best reference for that):• increased hemithoracic volume-mediastinal shift to the unaffected side • reduced hemithoracic volume-mediastinal shift to the affected side • normal hemithoracic volume-no mediastinal shiftThe differential diagnosis of an OH with increased volume includes large pleural effusions (which constitute the most frequent cause of OH) and large thoracic masses, especially in children. In most cases, these conditions can be easily differentiated by ultrasound or CT.The differential diagnosis of an OH with reduced volume includes pulmonary agenesis, pneumonectomy, and atelectasis. Bronchial obstruction by a foreign body (in children) or an endobronchial tumor (in adults) is the most common cause of atelectasis.There are cases in which an OH presents with normal volume. In children, such cases are primarily due to extensive pneumonia affecting the entire lung parenchyma. In adults, however, such cases are primarily due to bronchial carcinoma, accompanied by pleural effusion and atelectasis.Our patient presented with opacification of the left hemithorax with a marked mediastinal shift to the left. The absence of history of surgery or surgical scar on the chest wall, ruled out a previous pneumonectomy. A previous normal chest X-ray ruled out pulmonary agenesis. Therefore, a diagnosis of atelectasis was made, and a bronchoscopy revealed a tumor resulting in complete left main bronchial obstruction. . Note mediastinal structures, particularly the trachea, shifted to the left. Note also that the heart cannot be seen overlapping the vertebral bodies. These findings characterize an opaque hemithorax whose volume is reduced. RECOMMENDED READING1. Fraser RS, Müller NL, Colman NC, Pare PD, editors.

Left upper lobe atelectasis

“…Children are especially susceptible to resorption atelectasis in the presence of an aspirated foreign body because they have poorly developed collateral pathways for ventilation. 1 - 3 …”

“…The Golden S sign represents bowing or displacement of a fissure caused by a mass (generally bronchial carcinoma) that prevents complete displacement of the fissure. 1 - 3 …”

Diffuse opacification of the hemithorax

“…O HO com volume mantido tem como principais diagnósticos diferenciais pneumonias extensas, nas quais frequentemente broncograma aéreo é observado, e carcinoma broncogênico, com atelectasia e derrame pleural combinados, tendo efeitos antagônicos no volume do hemitórax comprometido. (1,2) Em nosso paciente, observa-se um HO à direita, com o mediastino centrado (volume mantido). Não havia história de infecção, nem a presença de broncograma aéreo, permitindo afastar a hipótese de pneumonia extensa.…”

Unilateral hyperlucent lung

“…In children, the main cause is obstruction by foreign body aspiration (FBA) 1 , whereas the main cause in adults is obstruction by neoplastic processes, particularly bronchial cancer. 2 The compromised lung may be with normal or hyperinflation. Hypoattenuation occurs only in cases of partial obstruction.…”