Radiographic Findings in Dogs With Patent Ductus Arteriosus: Left-to-Right, Right-to-Left, and Bidirectional Shunt

Patent ductus arteriosus (PDA) is a common congenital heart defect in dogs, typically presenting as a left-to-right (L-R) shunt. This multicenter retrospective study aimed to characterize thoracic radiographic changes in dogs with L-R, right-to-left (R-L), and bidirectional (BID) PDA. All dogs had an echocardiographic diagnosis of PDA and underwent thoracic radiography. Qualitative radiographic evaluations assessed left heart enlargement (LHE), right heart enlargement (RHE), main pulmonary artery dilation (MPAD), aortic dilation (AD), and lung patterns. Quantitative radiographic assessments included measurements of the vertebral heart score (VHS) and vertebral left atrial size (VLAS). A total of 22 dogs were included in the study (13 L-R, 6 R-L, and 3 BID). L-R and BID shunts demonstrated a significantly higher prevalence of LHE (p = 0.002) and lower prevalence of MPAD (p = 0.002) compared to R-L shunts, consistent with echocardiographic findings. All L-R cases exhibited RHE on radiography, although echocardiography only revealed LHE. R-L shunts were associated with a higher incidence of normal lung appearance compared to L-R and BID shunts (p = 0.018) and showed only RHE on radiographic evaluation. Finally, L-R PDA displayed significantly higher VHS and VLAS compared to R-L (p = 0.01 and 0.03, respectively). In conclusion, this study provides a detailed characterization of the thoracic radiographic alterations associated with PDA, highlighting differences based on the type of shunt and their correlation with echocardiographic findings.