Arteria praebronchialis found on MDCT: potentially dangerous aberrant artery supplying the left lower lobe

To describe the incidence and CT features of a rare branching pattern of the pulmonary artery, the Arteria praebronchialis (AP): According to the initial description, the AP originates as the first branch of the left pulmonary artery, crosses the front of the left mainstem bronchus and then runs along the mediastinal margin as it gives off branches to one or more of the basal segments.

Since the incidental discovery of the first patient, contrast-enhanced CT was screened by one radiologist for the presence of AP, until three more cases were identified. In those four patients, segmental and lobar branching patterns of the AP were assessed.

The estimated incidence of the AP was 0.03%. All four patients were men. Compared to the normal interlobar artery, the AP was smaller (n = 2), larger (n = 1), or of an equal size (n = 1). The segmental branches of the AP to the upper lobe (present in three patients) were A3 and A4 (n = 1), A3 and A5 (n = 1) and A4+5 (n = 1), respectively. Regarding the supply of the left lower lobe, AP gave off A7+8 and A9 (n = 2), A7+8 (n = 1), and A7 and A10 (n = 1), respectively. In two patients, a contralateral variant of pulmonary arterial branching was found, with (right) A7 arising as the first branch of right pulmonary artery.

The AP is extremely rare, but has a strong male predilection and highly diverse branching patterns in both the current study and the literature. Radiologists should familiarize themselves with the CT features of this surgically important variation, and be able to describe its lobar and segmental blood supply.