A hernia is a protrusion of a tissue, structure, or part of an organ through the muscle 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.
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
- anal hernias
- hernias of the nucleus pulposus of the intervertebral discs
- intracranial hernias
- Spigelian 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 or completely herniate into the chest.
- 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.
It is generally advisable to repair hernias quickly in order to prevent complications such as organ dysfunction, gangrene, multiple organ dysfunction syndrome, and death. 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 preferably 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 intensive 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.