Two Maltese dogs were referred for evaluation of a congenital heart disease: one was diagnosed with patent ductus arteriosus and the other was diagnosed with a ventricular septal defect. The PDA patient was diagnosed with congenital heart disease 2 weeks ago and the VSD patient about 11 months ago at another hospital. Echocardiographic findings revealed a bidirectional shunt condition, and the dogs were treated with medical management using sildenafil and oxygen inhalation. After medical management, the dogs returned to clinically normal conditions, and echocardiographic findings revealed a return to left-to-right shunt tendency. These dogs had no clinical signs associated with heart disease 3 years after treatment. This case report describes changes in echocardiography findings according to the progression of the reverse shunt and the possibility of improvement to a left-to-right shunt after medical treatment.

IntroductionCommon bile duct (CBD) measurements are important for the evaluation of biliary systemic disorders. However, in veterinary medicine, reference ranges for specific body weights (BW) and correlation between CBD diameter and BW have not been studied. This study aimed to establish normal reference ranges of CBD diameter for different BW groups and to analyse correlation between CBD diameter and BW in dogs without hepatobiliary disease. Additionally, normal reference ranges of CBD to aorta ratio (CBD: Ao ratio) were established which is not affected by BW.MethodsCBD diameter was measured at three different sites: porta hepatis (PH), duodenal papilla (DP) level and mid-portion (Mid) between these points using computed tomography (CT) in 283 dogs without hepatobiliary disease.ResultsThe reference range of CBD diameter at PH level: 1.69 ± 0.29 mm (Class 1; 1 kg ≤ BW < 5 kg), 1.92 ± 0.35 mm (Class 2; 5 kg ≤ BW < 10 kg), 2.20 ± 0.43 mm (Class 3; 10 kg ≤ BW < 15 kg), 2.79 ± 0.49 mm (Class 4; 15 kg ≤ BW < 30 kg); Mid-level: 2.06 ± 0.25 mm (Class 1), 2.43 ± 0.37 mm (Class 2), 2.74 ± 0.52 mm (Class 3), 3.14 ± 0.44 mm (Class 4); DP level: 2.33 ± 0.34 mm (Class 1), 2.90 ± 0.36 mm (Class 2), 3.35 ± 0.49 mm (Class 3), and 3.83 ± 0.50 mm (Class 4). There was a significant difference in CBD diameter at each level among all BW groups. Furthermore, BW and CBD diameter showed positive linear correlation at each level. We devised CBD: Ao ratio at each level that showed no significant difference between the different BW groups; PH level: 0.34 ± 0.05; Mid-level: 0.42 ± 0.06; DP level: 0.47 ± 0.06.ConclusionIn conclusion, since the CBD diameter for each BW is significantly different, different normal reference ranges of CBD diameter should be applied for each BW, and the CBD: Ao ratio can be used regardless of the BW.