hernia protrusion of an internal organ or part of an organ through the wall of a body cavity. The hernia is enclosed by a sac formed by the lining of the cavity. It results from a weakness or rupture in the wall, usually where there is already a natural weakness. A hernia may be present at birth or acquired later in life after heavy strain on the musculature. Structurally weak points, e.g., where various blood vessels, nerves, and ducts enter or leave a body cavity, occur in areas such as the lower abdomen, the diaphragm, and the region around the navel. If the protruding structure is caught in the muscular aperture of the wall, the result is a strangulation of the part, or an incarcerated hernia. Prompt medical attention must be received or loss of blood and eventual gangrene may result. A small hernia usually bulges spontaneously under exercise and strain and recedes into the cavity when the subject relaxes. A truss or external pad held against the weak spot may be used to control a hernia. However, surgery is usually recommended, even for a mild hernia, since it may eventually enlarge.

hernia A hernia is where a part of the abdominal content protrudes or bulges through an abnormal opening in the inner layers of the wall of the abdomen. The hernial ‘sac’ usually contains either fatty tissue or a loop of intestine. Some common types are groin, umbilical, and incisional hernias.

Groin hernias

There are two types of groin hernia, inguinal or femoral, the former being far more common and making up 98% of all groin hernias. Inguinal hernias are common in newborn boys, where they arise as a result of a ‘canal’ normally present in the embryo between the inside of the abdomen and the scrotum, which fails to close. They are also common in adult life and increase in frequency as one grows older. Inguinal hernias are approximately twenty times more common in men than women, while, interestingly, femoral hernias are more common in women.

Usually a groin hernia presents with a lump in the groin, felt all the time or only when straining. It often causes a dull ache that is worse with activity. The lump may get bigger with coughing or straining and shrink or disappear with lying down. Not all hernias are easily felt, however. When the contents can be pushed back into the abdomen the hernia is said to be ‘reducible’ — and ‘irreducible’ if not.

Surgeons have been treating and repairing hernias for over 3000 years, with varying degrees of success. The Mummy of Pharaoh Merneptah (nineteenth dynasty, 1224–14 bc) showed a large wound in the groin, with the scrotum separated from the body indicating that crude surgery had been performed on an inguinal hernia that had passed down into the scrotum. Nowadays many hernia repairs are performed worldwide each year, some 80 000 in the UK alone. The repair is usually performed by reinforcing the defect with stitches or a plastic mesh, often as a day case procedure, using either a local or a general anaesthetic.

While most hernias are usually just troublesome, on rare occasions they enlarge quickly with a sudden intense pain and part of the bowel gets trapped and becomes blocked. This intestinal obstruction is an emergency situation and requires surgery to free the trapped piece of bowel or to excise it if irretrievably damaged by ‘strangulation’ of its blood supply.

Umbilical hernias

Up to a fifth of babies are born with a bulge through a defect at the site of the umbilical cord. The majority will close by themselves and they only occasionally need surgical repair if the hernia becomes excessively large or inflamed, or if it is still present by the age of about four. Adults also develop hernias in the region of the umbilicus (paraumbilical). These are often associated with obesity, can be uncomfortable, and may become irreducible. Again they are usually repaired as a day case or overnight stay procedure.

Incisional hernias

These occur months or years after abdominal surgery and are common after such procedures as large bowel surgery in either sex, or hysterectomy in women. They are more common in obese patients or following a postoperative wound infection. They may become very large and unsightly. Rarely they may cause the bowel to obstruct and require emergency surgery. Nowadays they are usually repaired with a large piece of mesh, as there is a high recurrence rate after a sutured repair.

S. G. Taylor, and P. J. O'Dwyer

hernia Protrusion of an organ, or part of an organ, through its enclosing wall or connective tissue. Common hernias are a protrusion of an intestinal loop through the umbilicus (umbilical hernia), or protrusion of part of the stomach or oesophagus into the chest cavity (hiatus hernia).