Differential Diagnosis

The patient's presentation and imaging findings suggest several possible diagnoses. Here's a categorized differential diagnosis:

• Single most likely diagnosis
  • Pulmonary nodule: The chest x-ray shows an 8.5 cm diameter round, smooth-edged opacity, which is more consistent with a pulmonary nodule than other options. The patient's history of trauma and lack of respiratory symptoms make other diagnoses less likely.
• Other Likely diagnoses
  • Contusion of the lung: Given the patient's history of a motor vehicle collision, a lung contusion is possible, although the smooth-edged opacity on the chest x-ray is not typical for a contusion.
  • Pneumothorax: Although the patient does not have symptoms of a pneumothorax, such as shortness of breath or decreased breath sounds, it is still possible, especially given the trauma history.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Penetrating foreign body: Although the patient was a restrained front seat passenger and there are no reported lacerations or contusions, a penetrating foreign body could have occurred, and it is essential to consider this possibility to avoid missing a potentially life-threatening condition.
• Rare diagnoses
  • Lung cancer: Although the patient is young and healthy, lung cancer cannot be entirely ruled out, especially if the pulmonary nodule is found to be malignant. However, this diagnosis is less likely given the patient's age and lack of symptoms.
  • Other rare diagnoses, such as a pulmonary arteriovenous malformation or a congenital lung lesion, could also be considered, but they are less likely given the patient's presentation and imaging findings.