A hernia occurs when part of an internal organ or body part protrudes through an opening into another area where it ordinarily should not be located. There are many different types of hernias, but the most common is when a portion of the intestine protrudes through a weak area in the muscular wall of the abdomen. This causes an abnormal bulge under the skin of the abdomen, usually near the groin or the navel.
Hernias occur in various locations. Some hernias are present at birth, while others develop during adulthood. Hernias may enlarge due to increased pressure inside the abdomen, such as during straining, persistent coughing, obesity, or pregnancy.
Inguinal hernia — A portion of intestine or internal fat protrudes through a weakness in the inguinal canal. The inguinal canal is a natural passageway through the abdominal wall in the groin. In males, the inguinal canal contains the blood vessels that go to the testicle and the duct that carries sperm from the testicle. Inguinal hernias account for 75% of all hernias and are five times more common in males than females. They may be present in infants but can develop in adults also.
Femoral hernia — This is a hernia through the passage that contains the large blood vessels (the femoral artery and vein) between the abdomen and the thigh. This type of hernia causes a bulge in the upper thigh just under the groin and is more common in women than men.
Epigastric hernia — A small bit of fat bulges through a weakness in the upper abdominal muscles between the navel and breastbone. Most people with such hernias are between ages 20 and 50. These hernias are often so small that they may go unnoticed.
Umbilical hernia — Intestine or fat bulges through the abdominal wall under the navel. The area of weakness in the abdominal wall can be very small (less than half an inch) or it can be as large as 2 to 3 inches. Umbilical hernias are common in newborns but may disappear gradually over time. They may also occur in adults who are overweight or in women who have been pregnant many times.
Incisional hernia — Intestine bulges through a weakness in the abdominal wall in an area where there has been previous surgery. The skin has healed, but the underlying muscle has pulled apart, resulting in a hernia. These hernias can be small or quite large.
Ventral hernia — This is a general term that can refer to an epigastric, umbilical or incisional hernia.
Hiatus hernia — This hernia involves the stomach rather than the intestine. The stomach slips upward through the normal opening in the diaphragm and passes into the chest. It is often associated with acid reflux, or "gastroesophageal reflux disease" (GERD), which causes heartburn.