A hernia is a protrusion of a tissue, structure, or part of an organ through the muscular tissue or the membrane by which it is normally contained. The hernia has three parts: the orifice through which it herniates, the hernial sac, and its contents.
By far most hernias develop in the abdomen
, when a weakness in the abdominal wall evolves into a localized hole, or "defect", through which adipose tissue
, or abdominal organs covered with peritoneum
, may protrude. Another common hernia involves the intervertebral disc
, and causes back pain
Hernias 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 organ which has become "stuck" in the hernia, sometimes leading to organ dysfunction. Fatty tissue usually enters a hernia first, but it may be followed by or accompanied by an organ.
Most of the time, hernias develop when pressure in the compartment of the residing organ is increased, and the boundary is weak or weakened.
- Weakening of containing membranes or muscles is usually congenital (which explains part of the tendency of hernias to run in families), and increases with age (for example, degeneration of the annulus fibrosus of the intervertebral disc), but it may be on the basis of other illnesses, such as Ehlers-Danlos syndrome or Marfan syndrome, stretching of muscles during pregnancy, losing weight in obese people, etc., or because of scars from previous surgery.
- Many conditions chronically increase intra-abdominal pressure, (pregnancy, ascites, COPD, dyschezia, benign prostatic hypertrophy) and hence abdominal hernias are very frequent. Increased intracranial pressure can cause parts of the brain to herniate through narrowed portions of the cranial cavity or through the foramen magnum. Increased pressure on the intervertebral discs, as produced by heavy lifting or lifting with improper technique, increases the risk of herniation.
Hernias can be classified according to their anatomical location:
- abdominal hernias
- diaphragmatic hernias and hiatal hernias (for example, paraesophageal hernia of the stomach)
- pelvic hernias, for example, obturator hernia
- hernias of the nucleus pulposus of the intervertebral discs
- intracranial hernias
Each of the above hernias may be characterised by several aspects:
- congenital or acquired: congenital hernias occur prenatally or in the first year(s) of life, and are caused by a congenital defect, whereas acquired hernias develop later on in life. However, this may be on the basis of a locus minoris resistentiae (Lat. place of least resistance) that is congenital, but only becomes symptomatic later in life, when degeneration and increased stress (for example, increased abdominal pressure from coughing in COPD) provoke the hernia.
- complete or incomplete: for example, the stomach may partially herniate into the chest, or completely.
- internal or external: external ones herniate to the outside world, whereas internal hernias protrude from their normal compartment to another (for example, mesenteric hernias).
- intraparietal hernia: hernia that does not reach all the way to the subcutis, but only to the musculoaponeurotic layer. An example is a Spigelian hernia. Intraparietal hernias may produce less obvious bulging, and may be less easily detected on clinical examination.
- bilateral: in this case, simultaneous repair may be considered, sometimes even with a giant prosthetic reinforcement.
- irreducible (also known as incarcerated): the hernial contents cannot be returned to their normal site with simple manipulation.
If irreducible, hernias can develop several complications (hence, they can be complicated or uncomplicated):
- strangulation: pressure on the hernial contents may compromise blood supply (especially veins, with their low pressure, are sensitive, and venous congestion often results) and cause ischemia, and later necrosis and gangrene, which may become fatal.
- obstruction: for example, when a part of the bowel herniates, bowel contents can no longer pass the obstruction. This results in cramps, and later on vomiting, ileus, absence of flatus and absence of defecation. These signs mandate urgent surgery.
- dysfunction: another complication arises when the herniated organ itself, or surrounding organs start dysfunctioning (for example, sliding hernia of the stomach causing heartburn, lumbar disc hernia causing sciatic nerve pain, etc.).
It is generally advisable to repair hernias in a timely fashion, in order to prevent complications such as organ dysfunction, gangrene
, and multiple organ dysfunction syndrome
. Most abdominal hernias can be surgically repaired, and recovery rarely requires long-term changes in lifestyle. Uncomplicated hernias are principally repaired by pushing back, or "reducing", the herniated tissue, and then mending the weakness in muscle tissue (an operation called herniorrhaphy
). If complications have occurred, the surgeon will check the viability of the herniated organ, and resect it if necessary. Modern muscle reinforcement techniques involve synthetic materials (a mesh prosthesis) that avoid over-stretching of already weakened tissue (as in older, but still useful methods). The mesh is either placed over the defect (anterior repair) or more prefrably under the defect (posterior repair). At times staples are used to keep the mesh in place. These mesh repair methods are often called "Tension Free" repairs because, unlike older traditional methods, muscle is not pulled together under tension. Evidence suggests that these Tension Free methods have the lowest percentage of recurrences and the fastest recovery period compared to older suture repair methods. Increasingly, some repairs are performed through laparoscopes
Many patients are managed through day surgery centers, and are able to return to work within a week or two, while heavy activities are prohibited for a longer period. Patients who have their hernias repaired with mesh often recover in a number of days. Surgical complications have been estimated to be up to 10%, but most of them can be easily addressed. They include surgical site infections, nerve and blood vessel injuries, injury to nearby organs, and hernia recurrence.
Generally, the use of external devices to maintain reduction of the hernia without repairing the underlying defect (such as hernia trusses, trunks, belts, etc.), is not advised. Exceptions are uncomplicated incisional hernias that arise shortly after the operation (should only be operated after a few months), or inoperable patients.
It is essential that the hernia not be further irritated by carrying out strenuous labour.
A sportman's hernia
is a syndrome
characterized by chronic groin pain
and a dilated superficial ring
of the inguinal canal, although a true hernia is not present.
By far the most common hernias (up to 75% of all abdominal hernias) are the so-called inguinal hernias. For a thorough understanding of inguinal hernias, much insight is needed in the anatomy of the inguinal canal. Inguinal hernias are further divided into the more common indirect inguinal hernia (2/3, depicted here), in which the inguinal canal is entered via a congenital weakness at its entrance (the internal inguinal ring), and the direct inguinal hernia type (1/3), where the hernia contents push through a weak spot in the back wall of the inguinal canal. Inguinal hernias are more common in men than women while femoral hernias are more common in women.
Femoral hernias occur just below the inguinal ligament
, when abdominal contents pass into the weak area at the posterior wall of the femoral canal
. They can be hard to distinguish from the inguinal type (especially when ascending cephalad): however, they generally appear more rounded, and, in contrast to inguinal hernias, there is a strong female preponderance in femoral hernias. The incidence of strangulation in femoral hernias is high. Repair techniques are similar for femoral and inguinal hernia
Umbilical hernias are especially common in infants of African
descent, and occur more in boys. They involve protrusion of intraabdominal contents through a weakness at the site of passage of the umbilical cord
through the abdominal wall
. These hernias often resolve spontaneously.
Umbilical hernias in adults are largely acquired, and are more frequent in obese
women. Abnormal decussation of fibers at the linea alba
An incisional hernia occurs when the defect is the result of an incompletely healed surgical wound. When these occur in median laparotomy
incisions in the linea alba
, they are termed ventral hernias
. These can be the most frustrating and difficult to treat, as the repair utilizes already attenuated tissue.
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 this type, in which the normal passageway through which the esophagus meets the stomach (esophageal hiatus) serves as a functional "defect", allowing part of the stomach to (periodically) "herniate" into the chest. Hiatus hernias may be either "sliding," in which the gastroesophageal junction itself slides through the defect into the chest, or non-sliding (also known as para-esophageal), in which case the junction remains fixed while another portion of the stomach moves up through the defect. Non-sliding or para-esophageal hernias can be dangerous as they may allow the stomach to rotate and obstruct. Repair is usually advised.
A congenital diaphragmatic hernia is a distinct problem, occurring in up to 1 in 2000 births, and requiring pediatric surgery. Intestinal organs may herniate through several parts of the diaphragm, posterolateral (in Bochdalek's triangle, resulting in Bochdalek's hernia), or anteromedial-retrosternal (in the cleft of Larrey/Morgagni's foramen, resulting in Morgagni-Larrey hernia, or Morgagni's hernia).
Other types of hernia
Since many organs or parts of organs can herniate through many orifices, it is very difficult to give an exhaustive list of hernias, with all synonyms and eponyms
. The above article deals mostly with "visceral hernias", where the herniating tissue arises within the abdominal cavity. Other hernia types and unusual types of visceral hernias are listed below, in alphabetical order:
- Brain hernia: herniation of part of the brain because of excessive intracranial pressure. This may be a life-threatening condition, especially if the brain stem (responsible for some important vital signs) is involved.
- Cooper's hernia: a femoral hernia with two sacs, the first being in the femoral canal, and the second passing through a defect in the superficial fascia and appearing immediately beneath the skin.
- Epigastric hernia: a hernia through the linea alba above the umbilicus.
- Littre's hernia: a hernia involving a Meckel's diverticulum. It is named after the French anatomist Alexis Littre (1658-1726).
- Lumbar hernia: a hernia in the lumbar region (not to be confused with a lumbar disc hernia), contains the following entities:
- Petit's hernia - hernia through Petit's triangle (inferior lumbar triangle). It is named after French surgeon Jean Louis Petit (1674-1750).
- Grynfeltt's hernia - hernia through Grynfeltt-Lesshaft triangle (superior lumbar triangle). It is named after physician Joseph Grynfeltt (1840-1913).
- Obturator hernia: hernia through obturator canal
- Pantaloon hernia: a combined direct and indirect hernia, when the hernial sac protrudes on either side of the inferior epigastric vessels
- Perineal hernia: a perineal hernia protrudes through the muscles and fascia of the perineal floor. It may be primary but usually, is acquired following perineal prostatectomy, abdominoperineal resection of the rectum, or pelvic exenteration.
- Properitoneal hernia: rare hernia located directly above the peritoneum, for example, when part of an inguinal hernia projects from the deep inguinal ring to the preperitoneal space.
- Richter's hernia: strangulated hernia involving only one sidewall of the bowel, which can result in bowel perforation through ischaemia without causing bowel obstruction or any of its warning signs. It is named after German surgeon August Gottlieb Richter (1742-1812).
- Sliding hernia: occurs when an organ drags along part of the peritoneum, or, in other words, the organ is part of the hernia sac. The colon and the urinary bladder are often involved. The term also frequently refers to sliding hernias of the stomach.
- Sciatic hernia: this hernia in the greater sciatic foramen most commonly presents as an uncomfortable mass in the gluteal area. Bowel obstruction may also occur. This type of hernia is only a rare cause of sciatic neuralgia.
- Spigelian hernia, also known as spontaneous lateral ventral hernia
- Sports hernia, a hernia characterized by chronic groin pain in athletes and a dilated superficial ring of the inguinal canal.
- Velpeau hernia: a hernia in the groin in front of the femoral blood vessels
- Spinal disc herniation, or "herniated nucleus pulposus": a condition where the central weak part of the intervertebral disc, which helps absorb shocks to our spine), herniates through the fibrous band (annulus fibrosus) by which it is normally bound. This usually occurs low in the back at the lumbar or lumbo-sacral level and can cause back pain which usually radiates well into the thigh or leg. When the sciatic nerve is involved, the symptom complex is called sciatica. Herniation can occur in the cervical vertebrae too. A nucleoplasty is an operation to repair the herniation.
- Double hernia: the presence of a hiatus hernia with concomitant severe cardiorespiratory illness. The hernia itself poses no symptoms, but preoccupies the sufferer.
Complications may arise post-operation, including rejection of the mesh
that is used to repair the hernia. In the event of a mesh rejection, the mesh will very likely need to be removed. Mesh rejection can be detected by obvious, sometimes localised swelling and pain around the mesh area. Continuous discharge from the scar is likely for a while after the mesh has been removed.
An untreated hernia may complicate by:
- Surgical recall, 2nd edition, by Lorne. H. Blackbourne, published by Lippincott Williams & Wilkins
- Sabiston textbook of surgery, 17th edition, Townsend et.al.(e.d.), Elsevier-Saunders