What Is a Hernia?

A hernia is a protrusion of an organ or tissue through a hole. The hole is usually an abnormal opening that should not be there.  This is the case in the groin where an inguinal hernia occurs and through an incision where an incisional or ventral hernia occurs.  Another example is the umbilical or belly button hernia in which tissues, and possibly intestine, pass through an opening in the navel which did not close after birth.

Occasionally, a hernia occurs at the site of a normal opening that under normal circumstances does not allow tissue or organs to protrude through it.  Such is the case for a hiatal hernia, in which the stomach protrudes through the normal opening that allows the esophagus to pass from the chest into the abdomen.  A hernia through a normal opening occurs when the opening enlarges or when barriers to protrusion disappear.

Where do hernias occur?

A hernia can develop at any place there is a normal opening, an abnormal opening or a potential opening.

• A normal opening, for example,  would be the hole the esophagus passes through on its way from the chest to the abdomen.
• An abnormal opening is one that results from an incision.  For some reason the incision did not completely heal, leaving an opening.
• Potential openings result from the developmental process and are sites which at one time were open.  These sites should have closed during normal development.  If they do not, a potential hole exists through which tissue and organs can herniate.  Two examples of hernias through potential openings are the groin (inguinal) hernia and the umbilical hernia.

About umbilical hernias

An umbilical hernia arises through the site of the umbilical cord.  While in utero, the umbilical cord brings nutrients to and takes wastes from the fetus.  At birth, the umbilical cord is cut and then shrivels up.  If the site of the umbilical cord does not fuse solidly with the rest of the abdominal wall, a small hole is left.  With time, this hole can enlarge and allow the passage of tissue, forming an umbilical hernia.