What is a hernia?

A hernia is the exit of an organ, or part of an organ, or some other tissue from the space in which it normally resides through a defect or hole in a tissue wall.
Abdominal hernias occur due to a defect in the abdominal muscle wall and often result in a bulge felt under the skin of the abdomen.
The most common sites of a hernia are the groin (an inguinal hernia) and the navel (an umbilical hernia). Hernias may occur in other areas of the abdomen and may occur spontaneously or as a result of previous surgery (an incisional hernia). 
Once discovered, hernias should be repaired as they tend to enlarge, become painful, and may cause serious complications such as bowel gangrene if the bowel gets stuck in the defect.