Which of the following conditions is least likely to occur as secondary to a rib fracture?

Hydrothorax refers specifically to the presence of fluid in the pleural space that is typically due to conditions like congestive heart failure, malignancy, or infections, rather than trauma such as rib fractures. While rib fractures can lead to complications like hemothorax, which involves bleeding into the pleural cavity, or pneumothorax, where air enters the pleural space, hydrothorax is less directly associated as a secondary complication of rib fractures.

Hemothorax occurs when a rib fracture lacerates blood vessels, leading to blood accumulation between the pleurae. Pneumothorax can arise from a fractured rib penetrating the pleural cavity, allowing air to escape into the chest wall. Hypoxia may develop as a result of any of these thoracic complications, due to impaired gas exchange or ventilation. In contrast, hydrothorax is more distinctly related to systemic issues rather than isolated traumatic injuries like rib fractures, making it the condition least likely to occur as a secondary result of such fractures.