A supine trauma patient has a portable anteroposterior chest radiograph. There is increased lucency of the left costophrenic angle extending along the lateral abdominal wall with sharp demarcation of the diaphragm beneath it. Which condition does this indicate?
- A Left basal atelectasis
- B Left pneumothorax ✓
- C Left hydropneumothorax
- D Free intraperitoneal air
Correct answer: B. Left pneumothorax
Explanation
The deep sulcus sign describes abnormal deepening and lucency of the costophrenic sulcus on a supine radiograph, caused by air collecting anteriorly and laterally when the patient cannot sit upright. In the erect position this same air would rise to the apex as a visible visceral pleural line. Free intraperitoneal air instead outlines the underside of the diaphragm centrally, and basal atelectasis produces opacity rather than lucency.
Reference: Grainger and Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.