The anterior bronchus sign: a new clue to hilar abnormality

One hundred normal posteroanterior chest radiographs were reviewed to determine the frequency of appearance and characteristics of the anterior segmental bronchi of the upper lobes. The bronchus was visible as a sharp circle on the right in 45% of normals, and on the left in 50%. In 90% of normals, there is less than 3 mm of tissue lateral to the bronchus. In 10% of normals, pulmonary vessels may cause 3-5 mm of tissue lateral to the bronchus. Four cases of bronchogenic carcinoma were found to have more than 5 mm of tissue lateral to the bronchus. The presence of more than 5 mm of tissue lateral to the anterior segmental bronchus is termed the "anterior bronchus sign" and is a helpful clue to recognizing hilar region abnormality.