Abdominal Herniae

Definition

A hernia is generally defined as a protrusion of an organ or structure beyond the limits of its normal anatomical confines.  Herniae generally develop at a site of natural weakness in genetically predisposed individuals exposed to one or more risk factors.

Risk Factors & Causes

Inherited risk factors centre on genes that code for connective tissue proteins; genetically predisposed individuals have connective tissues with inherent weaknesses.  These conditions, as risk factors for hernia development, are still under investigation, and the causal relation is not clearly understood.

Any cause of increased intra-abdominal pressure can contribute to development of a hernia, including chronic straining due to heavy lifting, chronic straining at stool due to constipation or at urination due to an enlarged prostate, chronic coughing, intra-abdominal obesity, pregnancy, and tumours. Some medications that dampen the inflammatory response – such as steroids – can also contribute to development of a hernia, particularly at the site of a healing incision.

A hernia may also arise as a consequence of traumatic defects in otherwise healthy tissue, without longstanding increased intra-abdominal pressure.  The two main mechanisms are penetrating injuries causing tears in the muscle and blunt shearing forces applied to the muscle.  A third mechanism is a transient, extreme increase in intra-abdominal pressure.

Hernia Symptoms

The main symptom of an abdominal wall hernia is a visible or palpable lump or swelling.  The lump may come and go on its own, with certain postures or positions, or it may reduce in size in response to externally applied pressure.  When lumps can no longer be pushed back inside, they persist despite the application of pressure, and may herald development of complications, so need attention without undue delay.

An uncomplicated hernia rarely causes pain, but may be associated with discomfort, particularly after strenuous activity, long periods of standing or walking, climbing stairs, or towards the end of the day.  If a hernia becomes painful, reddened, warm, or tender to touch, such symptoms usually indicate the development of a complication that may require urgent attention.

Abdominal pain that is not necessarily related to the site of the hernia may indicate an evolving or incomplete bowel obstruction.  This is frequently the first sign of an internal hernia.  An established bowel obstruction may develop with any type of hernia, and is usually associated with nausea and vomiting, and an inability to pass a bowel motion or break wind.  In this situation, emergency surgery may be required to correct both problems.

Complications of Hernia

The risk of a hernia becoming complicated is related to the size of the defect as well as the contents of the hernia sac.  Depending on the hernia site and size, its contents may include fat, bowel, bladder, stomach, liver, pancreas, spleen, kidney, adrenal gland, or combinations of these structures.

A tighter defect – called the neck of the hernia – causes greater constriction, and increases the risk of herniated contents becoming incarcerated or irreducible (unable to be pushed back, or reduced, into their normal location), strangulated (their blood supply is compromised, threatening necrosis or death of tissue), or, in the case of hollow organs such as bowel, obstructed (the normal passage of food or fluid is blocked).

Development of hernia complications warrants higher surgical priority in the case of incarceration, or emergency surgery in the case of strangulation or obstruction.

Types of Hernia

Hernia development occurs most frequently in the groin, more often in males than females; about 40% occur on the right, 20% on the left, and 40% in both groins simultaneously.  A groin hernia can either be direct or indirect inguinal, or femoral, with a greater risk of complication development in that order.

The second most common site of hernia development is at a previous abdominal incision, as an acquired weakness in the musculature of the abdominal wall.  Diabetes and smoking are additional risk factors for incisional hernia development.  A para-stomal hernia is a type of incisional hernia occurring at the site of an ileostomy or colostomy.

Other common hernia types include umbilical, epigastric, and Spigelian hernia.  All of the above types are external, or abdominal wall herniae.

By contrast, internal herniae are not visible from the outside, although they are just as prone to the complications described previously, and can be either due to problems arising during gut development or as a result of surgery on the abdomen.

During foetal development, much of the gastrointestinal tract protrudes outside the abdominal cavity; to be able to fit back inside, it must undergo a series of rotations, and folds over itself, the investing layers of peritoneal lining fusing to obliterate any potential hernia spaces.  Inadequate or failed rotation or fusion gives rise to the potential for an internal hernia.  Internal herniae are uncommon, but the most frequent sites are around the duodenum and around the caecum.

Internal herniae can also arise as a result of changes in the configuration or orientation of the bowel as a result of abdominal surgery.  Adhesions between adjacent loops of bowel or fibrous bands between various intra-abdominal structures can also create tunnels through which other parts of the bowel can herniate.

Diaphragmatic herniae are a special class of internal hernia that can also arise either as a result of problems during the foetal development of the diaphragm – the sheet of muscle that separates the chest cavity from the abdomen – or from acquired conditions of the diaphragm.  A hernia occurring due to failed fusion of muscular elements at the back of the diaphragm is called a Bochdalek hernia, named after the Czech Anatomist and Pathologist, Vincenz Alexander Bochdalek (1801–1883), who first discovered it.  Occurring due to failed fusion of the muscular elements at the front of the diaphragm, a Morgagni hernia is named after the Italian anatomist Giovanni Battista Morgagni (1681 – 1771), who studied the development of this part of the diaphragm.  Surgical and other traumatic defects of the diaphragm can also give rise to a diaphragmatic hernia.

A hiatal hernia is a unique diaphragmatic hernia; the oesophageal hiatus is the diaphragmatic opening that permits passage of the oesophagus (food pipe) from the chest into the abdomen.  Normally, it cradles the oesophagus snugly, contributing to the mechanism that prevents acid reflux.  Weakening of the ligament between the hiatal muscle fibres of the diaphragm and the oesophagus leads to widening of the hiatus, which may become so extreme as to admit many of the upper abdominal organs (a para-oesophageal hernia), or contribute to the stomach twisting on itself and becoming blocked (gastric volvulus).  Even if small (a sliding hiatal hernia), however, it is often associated with gastro-oesophageal reflux, heartburn, and indigestion.

Diagnosing & Investigating a Hernia

External herniae are usually diagnosed by physical examination, but imaging with ultrasound or CT scanning may be necessary to delineate the extent of the defect, associated defects, contents of the hernia sac, and related structures, particularly if surgery to repair the hernia is being considered.  An MRI scan may also be used to investigate the possibility of inflammation or scarring, or hint at alternative diagnoses.

Not all imaging modalities are suitable for all hernia types.  Although many doctors will order an ultrasound scan to help diagnose a groin hernia, the diagnostic accuracy of this combination is only as good as a coin-toss at 50%.  A CT scan is essential for the diagnosis of an internal hernia, however.  The actual investigations ordered will depend on the findings at physical examination, the diagnostic approach of your doctor, previous and concurrent herniae, findings on other investigations, and the treatment options under consideration.

Treatment of Hernia

The only strategy that is effective is surgical repair of the hernia; a hernia will not get better by itself, or with any form of non-surgical treatment.  That is not to say that there are no alternatives, however.  It is important to balance the risk of surgery against the risk of doing nothing.  If the risk of surgery is greater than the risk of hernia complications, then it is safer not to repair the hernia.  Other forms of management, such as analgesia, a truss, or an abdominal binder may help alleviate symptoms associated with a hernia.

Hernia Surgery

The type of surgical procedure selected to repair a hernia depends on many factors, including the type of hernia, the tissues to be repaired and their functional characteristics, the size of the hernia defect and hernia sac, the contents of the hernia sac, the patient’s physical and health characteristics, and the surgeon’s expertise.  In some situations, use of a synthetic mesh might be required to diminish the possibility of hernia recurrence.  In others, use of mesh may be hazardous.  Much has been recently reported in the press about complications of mesh.  There are certainly aspects of deep concern in relation to some of these reports, but not all that has been reported has been accurate.  Many of the problems stem from inappropriate use of mesh, selection of the wrong mesh type for a particular application, and use of mesh in a way for which it was not designed.  The potential for use of mesh, its rationale, and the potential for complications arising from it will be discussed on an individual basis.

The surgical approach may take a variety of forms, depending on a number of factors, and the strategy may change during the course of the operation.  Traditionally, surgery is conducted through an open incision,  and this may still be the approach of choice for certain groin herniae, for instance.  For incisional and internal herniae, however, a laparoscopic approach is now fairly standard.  Robotic surgery is a new advance that may more patients to undergo effective surgery – particularly to repair complex incisional herniae – while avoiding the morbidity associated with an open operation.

The risks of hernia repair surgery depend on many factors, including the hernia site, and the method of repair. These will be discussed individually, as treatment is tailored to each individual patient. You should be sure that you understand the details of surgery as discussed, and ask as many questions as are required to clarify any difficulties completely.

The probability of success of surgery to repair a recurrent hernia diminishes with each successive attempt, which is why we have worked closely over almost the past decade with the Australian Hernia Institute, as well as with local, interstate and international collaborators to develop a comprehensive approach to complex hernia repair and abdominal wall reconstruction.

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