Recognition of a pneumothorax depends on the volume of air in the pleural space and the position of the body. On a supine radiograph a pneumothorax can be subtle and approximately 30% of pneumothoraces are undetected. A sign to look for is the 'deep sulcus sign'. It represents lucency of the lateral costophrenic angle extending toward the hypochondrium (Figure). The image is of a patient in the ICU who is on mechanical ventilation. There was an acute exacerbation of the dyspnoe. There is a deep sulcus sign on the left. Notice that the left hemidiaphragm is depressed. This is an important finding since it indicates a tension pneumothorax. #Clinical #Radiology #CXR #Pneumothorax #Tension #Deep #Sulcus #DeepSulcus #Sign #RadiologyAssistant
