[Topographic radiologic anatomy of the right subcarinal and retrobronchial pulmonary recess (author's transl)].

Depending on the size of the subcarinal and retrobronchial recess the medial wall of the right and perhaps the left main bronchus can be recognized. The medial extension of the recess is very variable. On lateral films with slight anterior rotation of the right shoulder, the posterior wall of the right main bronchus can be shown in 97% of patients. Awareness of this recess and its boundaries is essential for diagnosis of subcarinal and tracheobronchial node enlargement. The following 4 signs will assist in diagnosis: 1. The dorsal margin of enlarged nodes may be recognized posterior and inferior to the carina. 2. The posterior wall of the right main bronchus can no longer be seen. 3. The medial wall of the right main bronchus can no longer be seen. 4. Clearer demonstration of the right main bronchus or bronchus intermedius occurs, due to an "air bronchogram" effect. Due to the application of these 4 signs, enlargements of the subcarinal or tracheobronchial nodes can be recognized, at a stage where the tracheal bifurcation is not yet splayed, and when the nodes have not yet caused bronchostenosis.