
Although I have not had experience of umbilical hernias in dogs, I have seen it in children and in lambs.
I was told by a consultant surgeon that when the foetuses or foetus develops the internal organs develop first in a membrane, so they are held in place, next the muscle develops to cover this and finally the skin. In some babies and animals the muscle and skin development is slowed and this is when umbilical hernias develop. In children the conditions are often referred to as gastroschisis and exomphalos. In the former the membrane ruptures and the gut and organs are loose, in the latter the gut and organs are still in the membrane at birth.
The size of the hernia depends very much on how the development of muscle and skin slows. Some children need a patch to hold the gut and organs in place, while the muscle and skin grows over, in others a small operation shortly after birth is all that is needed to correct the problem.
There is an international charity which supports parents and children born with these conditions, if you visit their website some of the babies on the Experiences page are pictured while still under treatment, so if you are squeamish do bear this in mind.
www.GEEPS.co.uk
I was a founder member of GEEPS and their first chairperson, along with Sue Smith my friend whose daughter Sarah was born with gastroschisis.