Posterior wall of the bronchus intermedius: radiographic-CT correlation

The posterior wall of the bronchus intermedius (PWBI) is visible on lateral chest radiographs and computed tomographic (CT) scans and can become abnormally thickened in the presence of right hilar disease. The appearances of the PWBI on plain radiographs and CT were correlated in groups of 20 normal patients and 20 patients with a right hilar abnormality. Among 10 patients with an abnormal hilum who had thickening of the PWBI on CT, the lateral radiograph showed thickening of similar degrees in seven. However, in two of the 10, the lateral chest radiograph significantly underestimated the degree of thickening of the PWBI, and in one the PWBI was not visible. Among 10 patients with an abnormal right hilum who had no thickening of the PWBI on CT, the PWBI appeared to be abnormal on lateral chest radiographs in four because of adenopathy in the lateral or medial hilum. One other finding of note was the presence in one patient of an anomalous pulmonary vein passing posterior to the bronchus intermedius, simulating a small posterior hilar mass.