All the nutrients a puppy gets when inside its mother come from the placenta. This placenta connects the mothers blood to the puppies blood to allow nutrients for growth and development of the puppy. The placenta attaches to the puppies belly. As the abdominal wall develops this attachment becomes smaller and smaller until there is just a stalk (the umbilical cord) providing the nutrients from the placenta to the puppy via the belly button.
Shortly after birth the umbilical cord shrivels up and the small abdominal defect closes over. Failure of this abdominal wall closure is known as an umbilical hernia and it usually becomes apparent that this closure has failed by about 5 weeks of age.
As the puppy grows and the pressure inside the abdomen increases, parts of the abdomen can be forced out of this small hole. Usually this is just fat if the hole is quite small. If the hole is bigger then larger abdominal contents can be pushed through this hole, such as the intestines. If this happens then they can become constricted, preventing normal movement of food and could cause a life threatening problem that requires immediate surgery.
Umbilical hernias are usually congenital, caused by flawed development of the puppy when inside the mother. As the final hole closes over a few days after birth, it is very rare for the hernia to be due to “its mum bit the umbilical cord too short” as most breeders will suggest. It has generally been accepted that an umbilical hernia is a hereditary problem that is passed down from parents to puppies. This form of inheritance has been proven in collies, cocker spaniels, bull terriers, airdale terriers, basenji and Pekingese. It is likely that other breeds will pass on this trait in a similar way, it just may not have been investigated properly to prove it scientifically in other breeds.
As an umbilical hernia is a congenital defect due to a problem with development in the mothers uterus, a lot of animals have more than one defect (although not all can be detected at a young age on routine clinical examination by a vet – some become apparent later in life). Although the hernia is not usually a life threatening condition, heart defects can become life threatening as a puppy gets older. Many male dogs with umbilical hernias also have retained testicles.
If you are looking to buy a puppy, have a feel of its belly and if you can feel a small lump there, it is probably an umbilical hernia and it is best not buying a puppy with this condition, especially if you intend to breed.
As the umbilical hernia has the potential to cause life threatening problems and also predisposes to other life threatening defects and is passed on to offspring, at St Clair Veterinary Care we recommend neutering all animals with an umbilical hernia, the hernia can then be repaired at the time of neutering.