http://www.upei.ca/cidd/Diseases/car...seases/PDA.htm
Here is an excellent site that explains this rather complicated problem. I used to be a labor & del. nurse and we dealt with this in skin babies and the problem is about the same with dogs. Please read this and hopefully it will help with knowing which type to ask about or at least knowing when the vet expains it. Please keep us posted. Sending lots of prayers and kisses from Yogi and Dori too.