The protrusion of an organ, or part of an organ, through the wall of the cavity that normally contains it. The most common types of hernia involve the organs of the abdomen which can herniate externally through the abdominal wall, or internally usually through a defect in the diaphragm. External hernias appear as a swelling, covered with skin, which bulges on coughing or straining but which can normally be made to disappear with gentle pressure.
Inguinal hernia appears in the groin; less common is femoral hernia, which appears just below the groin. Incisional hernia may occur through a defect in any abdominal surgical scar, a paraumbilical hernia arising just to the side of the umbilicus and an epigastric hernia in the mid line above the umbilicus. In children, herniation may occur through the umbilicus itself, which is a natural weak spot. The commonest internal hernia is a hiatus hernia, when part of the stomach slips upwards into the chest through the DIAPHRAGM (see diagram).
Hernias may be due to a defect present at birth (congenital), or may develop later in life (acquired). Acquired hernias arise due to the development of a defect or injury of the abdominal wall or due to increased pressure within the abdominal cavity, which forces the organ through a potential weakness. Such causes include chronic coughing or excessive straining due to constipation.
Small hernias may cause no problems at all. However, some may be large and cumbersome, or may give rise to a dragging sensation or even pain.
Although most reduce spontaneously under the effects of gravity or gentle pressure, abdominal organs that may have been displaced inside some hernias may become stuck, when they are said to be irreducible. If the contents become so trapped that their blood supply is cut off, then strangulation occurs. This is a surgical emergency because the strangulated organs will soon die or rupture. When strangulation – usually of a loop of intestine – does occur, the hernia becomes irreducible, red, and very painful. If the hernia contains bowel, then the bowel may also become obstructed.
Anatomy of indirect inguinal hernia: area 11 is where the displaced loop of intestine intrudes into the scrotum.
Surgical repair by laparoscopy or open operation consists of returning the herniated organs to their proper place and then repairing the defect through which the hernia occurred, sometimes incorporating a mesh to prevent recurrence. This may be done safely under local or general anaesthetic, often as a day-case procedure, and most operative repairs result in a permanent cure. Non-operative treatment with a compression belt, or truss, is used only for those unfit for surgery or while awaiting surgery.