A patent ductus arteriosus (PDA) was detected in a 10-month-old Pyrenean Shepherd. The PDA was occluded with hemostatic clips. One month after surgery, an aneurysmal dilatation of the ductus was diagnosed using Doppler echocardiography. The authors present the echo-Doppler findings and the follow-up of the ductus aneurysm. The pathogenesis and significance of such an aneurysm are discussed.