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Hernia
Image Notes: Frontal chest X-ray showing a hernia of Morgagni.
See Also: Incisional Hernia
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 3 parts: the orifice through which it herniates, the hernial sac, and its contents.
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.
Pathophysiology
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 or sciatica.
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.
Epidemiology
Between 1995 and 2005, 16,742 Americans died from hernias.
Characteristics
Hernias can be classified according to their anatomical location:
Examples include:
- 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 on 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 produces 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.
- reducible or irreducible (also known as incarcerated): the hernial contents can or 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.
- 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.)
Text and images are licensed under the GNU Free Documentation License. Material is used from the Wikipedia article "Hernia".
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