I know it is a little old
My boy has the same thing so I have researched it and talked to my vet.
Conventional wisdom, however, does not differentiate between "true hernias" where there is a defect in the body wall, and "delayed closures", where a small bit of omentum slips out of the area before the umbilicus closes.
The most common means of acquiring an umbilical hernia (delayed closure) is as a result of the umbilical cord being severed too close to the abdominal wall, when the mama dog bites off the umbilical cord too closely or is rough with the pup while whelping. Or that an area around the umbilical cord and belly simply did not grow fully closed and fuse together normally.
Most don't need to be fixed the are just cosmetic, fatty tissue gets trapped outside when closing and leaves a bump (outie belly button)
This type of hernia will not alter or hinder their lifestyle in any way. Keep in mind that a pup who acquires a hernia can still lead a healthy
More info
http://www.showdogsupersite.com/kenl...umbilical.html