A hernia can look concerning at first; a big, round lump simply does not belong on a puppy's belly. In some cases, a hernia can lead to a life-threatening illness, but in most cases, it is just a minor annoyance that can be easily fixed. If you suspect your puppy has a hernia, bring it to the attention of your vet.
A hernia occurs when there is an abnormal opening in the abdominal wall, and abdominal tissues are able to push their way through to just underneath the skin, producing a small external lump. If the hernia is small enough that only fat can get through, it is not an urgent problem. The emergency arises when the opening is big enough that a loop of intestine can poke through and get stuck, causing intestinal strangulation.
A hernia will appear as a fleshy lump on the puppy's belly, either where the bellybutton should be or where the hind leg meets the abdomen. Most hernias are normal-flesh-coloured, but if the lump appears irritated or inflamed or feels hot to the touch, intestinal strangulation may already be occurring. If this is the case, the puppy might be vomiting and running a fever and should be taken to a vet immediately.
The vet will visually examine the hernia and attempt to press the lump back into the abdomen with her finger. If it does go back in, it means that only fat was poking through, and the hernia is not an emergency. If the lump feels firm and warm, she will likely run bloodwork and take x-rays to determine the extent of the problem.
Surgical correction is the only way to repair a hernia, but not all hernias need to be repaired. Some small hernias close themselves by the time the puppy is six months old, and other, very small, hernias never need to be closed at all. Most vets schedule hernia repair for the same day as the spay or neuter surgery. If the hernia is large, however, it should be closed immediately. If intestinal strangulation has already begun, a couple of days of intensive post-operative care will be required.
Most puppies aren't bothered too much by hernias and to recover from the surgery rather quickly. Even puppies with larger hernias involving intestinal strangulation can recover from surgery just fine--but an untreated large hernia can be fatal within 48 hours of the onset of intestinal strangulation. Hernias are hereditary, and any dog who has had a hernia should not be used for breeding or show.