RUL=right upper lobe T= Thoracic vertebra

Figure 1 Normal anatomy of trachea (a), tracheal stenosis with normal branching of major bronchi (b), tracheal stenosis with an accessory tracheal right upper lobe branch (c) and tracheal stenosis with partial supply of right upper lobe (apical branch)  by tracheal bronchus (d). RUL = right upper lobe. LMB= left main bronchus. RMB = right main bronchus.