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Difficulty: MediumInterpreting Imaging Results

A 34-year-old man is brought to the emergency department after a high-speed motor vehicle collision. He complains of severe shortness of breath and right-sided chest pain. He is fully immobilized on a backboard with a cervical collar in place. Vital signs include a blood pressure of 115/75 mm Hg, pulse of 112/min, and respiratory rate of 28/min. Physical examination reveals decreased breath sounds over the right hemithorax. The trachea is midline, and there is no jugular venous distention. Because the patient cannot sit upright due to strict spine precautions, a supine portable anteroposterior chest radiograph is obtained. The image demonstrates a markedly radiolucent and abnormally deepened right costophrenic angle extending toward the hypochondrium. The apical visceral pleural line is not clearly visible. Which of the following is the most likely diagnosis based on this specific radiographic finding?

  1. Right-sided pneumothoraxAnswer
  2. B
    Right-sided hemothorax
  3. C
    Right-sided diaphragmatic rupture
  4. D
    Pneumoperitoneum
  5. E
    Right lower lobe pulmonary contusion

Answer

Right-sided pneumothorax
The correct diagnosis is a right-sided pneumothorax. On a supine anteroposterior chest radiograph, intrapleural air accumulates in the highest parts of the chest, which anatomically are the anterior and basal regions. This abnormal collection of air pushes the costophrenic angle inferiorly and makes it appear excessively radiolucent and deep. This finding is known as the 'deep sulcus sign' and is a classic, vital indicator of a pneumothorax in trauma patients who must remain supine.

Step-by-Step Solution

1
Analyze the clinical presentation and physical exam findings.
The patient has blunt chest trauma, tachycardia, tachypnea, and decreased breath sounds on the right hemithorax.
This establishes a high clinical suspicion for thoracic injury, specifically pneumothorax, hemothorax, or pulmonary contusion.
2
Interpret the specific radiographic findings described in the context of patient positioning.
The radiograph is taken supine. It shows a markedly radiolucent, abnormally deep right costophrenic angle (deep sulcus sign) without a visible apical pleural line.
Patient positioning dictates where air and fluid distribute. In an upright patient, air rises to the apex. In a supine patient, air accumulates in the least dependent areas: the anterior and basal pleura.
3
Correlate the imaging sign with the correct pathology.
The deep sulcus sign specifically represents basally accumulating pleural air on a supine radiograph, diagnosing a pneumothorax.
Differentiating this radiolucency from opacifications (which would suggest fluid/blood or contusion) secures the diagnosis.

Key Concept

The deep sulcus sign on a supine chest radiograph indicates a pneumothorax due to the anterior and basal accumulation of pleural air.
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Interpreting Imaging Results

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