An 8-year-old child recovering from blunt chest trauma shows diminished breath sounds on one side. What is the next recommended step for evaluation?

In the context of an 8-year-old child recovering from blunt chest trauma who exhibits diminished breath sounds on one side, the most appropriate next step for evaluation is a chest x-ray. This imaging modality is crucial in identifying possible complications from trauma, such as pneumothorax, hemothorax, or consolidation due to pulmonary contusion.

A chest x-ray provides a quick and effective assessment of the thoracic cavity and can help visualize any abnormalities in lung expansion, fluid levels, or the presence of air in the pleural space. Given the history of chest trauma and the present clinical signs, the chest x-ray serves as an essential tool for prompt diagnosis and management of the child's condition.

Other evaluation methods, while valuable in different contexts, would not be the best immediate choice here. For example, transillumination is primarily used in neonates to assess for pneumothorax, and may not be as accurate in older children. An echocardiogram is more suited for assessing cardiac conditions rather than direct lung issues. A lateral decubitus x-ray is useful for specific conditions like detecting free air or fluid but is generally performed after a standard chest x-ray if further investigation is warranted.