Systemic arterial supply to normal basal segments of left lower lobe: CT findings.

Objective: The purpose of this study was to evaluate the usefulness of CT in making a diagnosis of systemic arterial supply to normal basal segments of the left lower lobe.

Methods: We retrospectively reviewed chest radiography (three cases), CT (three cases), and angiography (two cases).

Results: An anomalous systemic artery arising from the descending aorta was shown as a retrocardiac density on posteroanterior radiography and as a nodular density behind the heart on lateral radiography. Contrast enhanced CT revealed the vascular nature of the density adjacent to the descending aorta. Dynamic CT in one patient demonstrated that the nodular density was composed of an anomalous systemic artery and a prominent inferior pulmonary vein. High-resolution CT showed the interlobar artery distal to the origin of the superior segmental artery to be absent. The bronchial system of the left basal segments was normal as was the pulmonary parenchyma on CT.

Conclusions: Characteristic CT findings consist of absence of the interlobar artery distal to the origin of the superior segmental artery and origination of an anomalous artery from the descending aorta that gives off branches to normal left basal segments. With a constellation of these CT findings, angiography would be obviated for definite diagnosis of this anomaly.