A hernia is a protrusion of an organ or tissue out of the body cavity in which it normally lies. By far the most common hernias develop in the abdomen, when a weakness in the abdominal wall evolves into a localized hole, or "defect", through which the protrusion occurs. These may present either with pain at the site, a visible or palpable lump, or in some cases by more vague symptoms resulting from pressure on an intraabdominal organ which has become "stuck" in the hernia. Fatty tissue usually enters a hernia first, but it may be followed by or accompanied by a segment of intestine or other intraabdominal organ. It is generally advisable to repair hernias in a timely fashion, in order to prevent complications which include intestinal blockage, gangrene, and death. Most hernias can be surgically repaired. Recovery rarely requires long-term changes in lifestyle.
A hernia may be likened to a failure in the sidewall of a pneumatic tire. The tire's inner tube behaves like the organ and the sidewall like the body cavity wall providing the restraint. A weakness in the sidewall allows a bulge to develop, which can become a split, allowing the inner tube to protrude, and leading to the eventual failure of the tire.
Types of hernias
By far the most common abdominal hernias are the so-called inguinal hernias. Named for the Latin word for "groin", these involve the bulging of abdominal contents into a defect in the inguinal canal in the lower abdomen. Since they involve the embryological route of descent of the testicle, inguinal hernias are more common in males than females, and in males the hernia contents commonly enter the scrotum. Inguinal hernias are further divided into the more common "indirect inguinal hernia", in which the inguinal canal is entered via a congenital weakness at its apex, and the "direct" type, where the hernia contents push through a weak spot in its back wall.
Other abdominal hernias include umbilical, femoral, incisional, and diaphragmatic. Umbilical hernias, especially common in infants of African descent, involve protrusion of intraabdominal contents through a weakness at the site of passage of the umbilical cord through the abdominal wall. While these often resolve spontaneously in children, in some communities mothers routinely push the small bulge back in and tape a coin over the palpable hernia hole until closure occurs. This practice is not medically recommended as there is a small risk of trapping a loop of bowel under part of the coin resulting in a small area of ischaemic bowel.
Femoral hernias, which can be virtually indistinguishable from the inguinal type, occur just below the groin crease, when abdominal contents pass into the weak area created by the passage of the femoral blood vessels into the lower extremities. An "incisional hernia" occurs when the defect is the result of an incompletely healed surgical wound. Higher in the abdomen, an (internal) "diaphragmatic hernia" results when part of the stomach or intestine protrudes into the chest cavity through a defect in the diaphragm. A hiatus hernia is a particular variant of the latter in which the normal passageway through which the esophagus meets the stomach serves as a functional "defect", allowing part of the stomach to periodically "herniate" into the chest.
Hernias may be surgically repaired by pushing back the abdominal tissue, and then repairing the weakness in muscle tissue. Modern techniques involve synthetic materials that avoid over-stretching of already weakened tissue, and repairs performed through laparoscopes. Many patients are able to return to work within a week or two, while heavy activities are prohibited for a longer period.
As above, hernias are primarily described by location. Each type can be further categorized as:
- reducible - the hernial contents can be returned to their normal site
- irreducible (incarcerated) - the contents cannot be "reduced" to their correct location
- strangulated - incarcerated hernia resulting in interrupted blood supply, or ischaemia, of contents; often associated with signs and symptoms of intestinal obstruction; these demand emergency surgery
- complete hernia - hernia sac and contents protrude all the way through the defect
- incomplete hernia - hernial contents do not protrude completely
Other types of hernia
- sliding hernia - the hernia sac is partially formed by the wall of a viscus
- Littre's hernia - hernia involving a Meckel's diverticulum
- Spigelian hernia - hernia through the linea semilunaris (spigelian fascia); a.k.a. spontaneous lateral ventral hernia
- internal hernia - hernia into or involving an intraabdominal structure
- obturator hernia - hernia through obturator canal
- lumbar hernia
- Petit's hernia - hernia through Petit's triangle (inferior lumbar triangle)
- Grynfeltt's hernia - hernia through Grynfeltt-Lesshaft triangle (superior lumbar triangle)
- pantaloon hernia
- ventral hernia
- Richter's hernia - incarcerated or strangulated hernia involving only one sidewall of the bowel. can result in bowel perforation through ischaemia without causing bowel obstruction.
- epigastric hernia - hernia through the linea alba above the umbilicus
- intraparietal hernia
- Hesselbach's hernia
- Congenital Diaphragmatic Hernia
- Bochdalek's hernia
- Morgagni's hernia
- propertitoneal hernia
- Cooper's hernia
- perineal hernia