Patent ductus arteriosus (PDA) is the most common congenital heart disease in dogs. The ductus arteriosus
extends from the main pulmonary artery to the descending aorta, shunting blood away from the nonfunctional
lungs in neonates. When it fails to constrict after birth, oxygenated blood can flow from the aorta to the pulmonary
artery. Most of untreated patients develop congestive heart failure at one year of age. The treatment options
include both minimally invasive and open surgical techniques. It is recommended that PDA be promptly closed
after diagnosis as immature dogs are the best candidates for surgery. An adult Pomeranian with PDA was
referred to Prasu-Arthorn Animal Hospital, Faculty of Veterinary Science, Mahidol University. An open surgical
ligation was performed at the animal hospital with the cooperation of a diplomate of the Thai Board of
Thoracic Surgery from the Faculty of Medicine Ramathibodi Hospital, Mahidol University. No intraoperative
complications occurred. Postoperative echocardiograms showed no residual flow, and there was a gradual
decrease in heart size three days to two months after surgery. The dog was more energetic and healthier.