Hernias occur when layers of the abdominal muscle become weak or tear. Abdominal pressure then pushes the lining of the abdominal wall out through the area of weakness, creating a bulge under the skin. A hernia may start as a small lump, but over time can grow large and may require surgical repair.
Even after surgical repair, hernias often recur. Implantation of a surgical mesh can help; recurrence rates for adults are lower in clinical literature when mesh is used. However, hernia occurrence and recurrence remain a consistent problem following abdominal surgery, with unacceptably high rates. A primary cause of failure is that sutures placed during the repair surgery can cut or pull through the tissue or mesh. Often hernias form at the location of a prior surgery where an incision occurred, when the abdominal pressure overcomes the strength of the closed surgical site. Thus these hernias are often called "incisional hernias" and are one of the most common types of hernias.