The anterior wall stripe of the left lower lobe bronchus on the lateral chest radiograph: CT correlative study

We designed a study to determine whether thickening or effacement of the anterior wall stripe of the left lower lobe bronchus on the lateral chest radiograph implies adjacent disease, as it does for the posterior wall stripe of the right bronchus intermedius. The anterior wall stripe of the left lower lobe bronchus originates from the inferior anterior aspect of the end-on left bronchus and descends in a gentle posteriorly convex curve. The left lower lobe bronchus was identified on routine lateral chest films in 86 of 90 consecutive patients who also had chest CT. In those cases the anterior wall stripe was measured and categorized on chest films. On the CT scans, the length of the left lower lobe bronchus and its relationship to the left lower lobe artery and left upper lobe, lingular, and lower lobe veins were assessed. The presence of adjacent disease was noted. A complete anterior wall stripe was seen in 59 of 86 cases. It was effaced by anterior soft tissue in 15 of 86 cases; in 12 of 86 cases only the superior 0.5-1.5 cm was effaced. A normal anterior wall stripe was as thick as 12 mm in one case, but was 6 mm or less in 90%. Shapes other than linear were common. Anatomic variation accounted for nearly all of these findings. There was no focal abnormality in the 12 cases with partial effacement or in nine of the 15 cases with complete effacement; disease was significant in only two of these six. We concluded that thickening or effacement of the anterior wall stripe is an unreliable sign of disease.