Anomalous systemic artery to the non-sequestrated lung: multi-slice computed tomography features

Anomalous systemic artery to the non-sequestrated lung (ASANSL) is a rare congenital anomaly that was previously classified as a Pryce type I sequestration; it comprises an anomalous systemic artery (ASA) to the normal lung.1 To more clearly determine the features of ASANSL, we collected data on 15 cases and reviewed the relevant literature. It has been concluded that multi-slice computed tomography (MSCT) can be used as a highly reliable and minimally invasive tool for diagnosing ASANSL and planning the treatment plan. A total of 15 patients with ASANSL who underwent contrast-enhanced MSCT were evaluated retrospectively. ASAs originating from the descending aorta and with normal bronchial connections were seen in all cases. Supply of an ASA to the left lower lung (LLL) was seen in 13 cases (13/15), with two cases to the right lower lobe (RLL, 2/15); 12 cases to all basal segments of LLL (12/15), and three cases to part of segments of LLL or RLL (3/15). Normal pulmonary parenchyma (3/15), as well as various abnormalities of pulmonary parenchyma, was also noted in the involved segments. Representative images are shown in Figure 1. Five cases were treated with division of the ASA followed by lobectomy. One patient opted for therapeutic embolization and nine selected follow-up.Figure 1: Representative images of patients with anomalous systemic artery to the non-sequestrated lung. Upper panel: A 26-year-old man presented with anomalous systemic artery to the non-sequestrated lung. Anomalous systemic artery (ASA) supply could be seen to all the basal segments of the left lower lung (LLL). (A) Axial computed tomography (CT) image of the LLL shows an ASA originating from the descending aorta, accompanied with a dilated left inferior pulmonary vein. (B) Axial CT image at the lung window in the LLL shows normal bronchi and ground-glass opacity (GGO). (C) and (D) volume rendering (VR) image and schematic diagram show an ASA to all basal segments of LLL, without pulmonary artery, and a normal bronchial tree. Lower panel: An asymptomatic 41-year-old woman with anomalous systemic artery to the non-sequestrated lung. ASA supply could be seen to parts of the segments of the right lower lung (RLL). (E) and (F), Axial CT images show that segments 8 + 9 were normal, and segments 7 + 10 were GGO. (G–I), VR images and schematic diagram show ASA to segments 7 + 10 of RLL, with normal bronchial tree.Pryce1 described three variants of sequestration: namely, an abnormal artery confined to a normally connected lung, an abnormal artery to both a sequestered mass and adjacent normal lung, and an abnormal artery to the sequestered mass. Multiple names have been used for this anomaly, and the staggeringly long list includes entries such as ASA to the left lower lobe, ASA supply to the normal basal segments of LLL, and pseudosequestration,2,3 which suggests that there remains a considerable amount of confusion regarding this condition. We think that ASANSL may be the most accurate term. In our series, the majority of cases involved all basal segments of LLL, which seems in line with the above mentioned term. However, in three cases, only part of the LLL or RLL segments was affected. Thus, definitively naming the condition as LLL would not seem to encapsulate the entire spectrum of what may occur and could be seen as unscientific. In addition, while using MSCT on the affected segment of the lung, changes in parenchyma could be noted, including atelectasis, emphysema, bronchiectasis, and areas of ground-glass opacity, indicating a slight pulmonary congestion caused by high systemic arterial pressure. It would thus be unscientific to classify such conditions as being completely normal. In the past, it was usually necessary to undergo angiography, but recently, MSCT imaging has generally been the most useful diagnostic method in the evaluation of patients suspected to have the above mentioned abnormality, as it demonstrates the bronchial and parenchyma, as well as vascular anatomy of the lung. Various treatment modalities have been described, including ligation or division of the ASA routinely followed by resection of the diseased segments of the lung, embolization of the ASA, and re-implantation of the ASA to the pulmonary artery. In conclusion, MSCT is a non-invasive and valuable method to diagnose ASANSL and may be of great value in the determination of the treatment plan. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Conflicts of interest None.