CT morphology of anomalous systemic arterial supply to normal lung in dogs

Anomalous systemic arterial supply to the normal lung (ASANL) is a rare congenital anomaly in humans, in which the systemic arteries supply the basal segments of the lower lobe. It has a normal bronchial connection, but lacks a normal pulmonary artery. This anomaly has not been previously reported in the veterinary literature. The objectives of this retrospective descriptive study were to characterize the CT findings and clinical features of ASANL , and to determine the breed predisposition in a population of referral canine cases. Thoracic CT images, in which the caudal lung lobes were fully inflated and the pulmonary artery could be traced to the periphery, were reviewed. A total of 1,950 dogs were enrolled, and the aberrant vasculature equivalent to ASANL in humans was detected in 48 dogs. Shetland Sheepdogs (7/48, odds ratio [OR] = 8.0, P < 0.00001), Miniature Dachshunds (19/48, OR = 3.9, P < 0.00001), and Labrador Retrievers (6/48, OR = 4.5, P = 0.0009) were over-represented. The affected lung lobes were the right caudal lobe (24/48, 50%), the left caudal lobe (21/48, 43.8%), and bilateral caudal lobes (3/48, 6.3%). The aberrant vessels originated from the left gastric artery (14/48), descending thoracic aorta (8/48), celiac artery (6/48), and splenic artery (1/48). In the remaining 19 cases, the origin of the aberrant vessels could not be determined. Although the clinical significance of ASANL in dogs remains unclear, surgeons should be aware of this finding prior to lobectomy of the caudal lung lobes to avoid intraoperative systemic arterial bleeding.