HERNIAS

Abdominal incisional hernias are common after operations requiring a large incision. These can be at the umbilicus, above the umbilicus (epigastric) or along the full length of the incision (massive ventral hernia) (figure 1).

In severe cases, portions of organs may move through the hole in the muscle.

How do they form?

During surgery an incision is made in the muscles that make up the abdomen. For some reason, that muscle doesn't heal, so a gap opens up as the muscles tighten and release during activities. Instead of a flat, strong piece of muscle, you have a piece of muscle that has a small gap in it. After a while, the tissues underneath realize there is an escape route through the muscle, and they start to poke through the opening, where they can be felt under the skin.

Who is at risk for an incisional hernia?

Incisional hernias are more common in obese and pregnant patients. Previous multiple abdominal surgeries may increase the risk of an incisional hernia.

Significant weight after an abdominal surgery is a risk factor as is, pregnancy or participation in activities that increase abdominal pressure like heavy lifting.

The incision is weakest, and most prone to a hernia, during the first 6-12 weeks after surgery while it is still healing. While incisional hernias can develop or enlarge months or years after surgery, they are most likely to occur in the first 6-12 weeks following surgery.

Diagnosing an incisional hernia

Incisional hernias may seem to appear and disappear, which is referred to as a "reducible" hernia.

The hernia may not be noticeable unless the patient is involved in an activity that increases abdominal pressure, such as coughing, sneezing, pushing to have a bowel movement, or lifting a heavy object.

CT scan or ultrasound is sometimes necessary to determine the extent of the hernia as well as its contents. Sometimes these imaging modalities also determine synchronous hernias nearby.

Incisional hernia treatment

An incisional hernia may not be symptomatic and small enough that surgical repair is an option. If the hernia is large, causes pain or is steadily growing, surgery may be recommended. Another option is a truss, a garment that is similar to a weight belt or girdle, that applies constant pressure to the hernia.

When is incisional hernia surgery necessary?

An Incisional hernia may require surgery if it is painful, enlarges over time, is cosmetically unappealing, or irreducible. In many cases surgery can be performed laparoscopically with small key-hole incisions.

A stomal hernia (also called a para-stomal hernia) is a type of incisional hernia that occurs next to a stoma. It is a common problem, and can be challenging to manage.

Cause

Stomal hernias result when there is a widening of the surgical hole (trephine) created in the abdominal wall at the time of original stoma formation. This hernia results from tangential forces that stretch on the trephine over time. They are a common and difficult complication to manage. In fact, some degree of herniation is argued to be inevitable, and does not always represent a true hernia.

Incidence

As a general rule, up to half of stomas will develop a para-stomal hernia, and most occur within the first two years.

Definition

A parastomal hernia is a protrusion of abdominal contents (commonly bowel or fatty omentum) through a weakness in the abdominal wall at the site of the previous hole (trephine) made for delivering the stoma. They are traditionally classified clinically into four sub-types:

1. Subcutaneous – the hernia occurs alongside the bowel for the stoma and bulges into the fatty spaced just under the skin (subcutaneous space).
2. Interstitial – the hernia occurs alongside the bowel for the stoma, then bulges into the abdominal wall sliding between the muscles of the abdominal.
3. Perstomal – relates only to the prolapsing loop stoma, and is where loops of bowel and or omentum enter the hernia space produced between the two loops of prolapsed bowel.
4. Intrastomal – the hernia occurs alongside the bowel for the stoma and enters the plane between the emerging and the everted part of the bowel. It typically occurs in prolapsing end stomas or stomas with excessive spouting.

The actual type of hernia is not as important as the contents of the hernia, and whether or not the hernia causes symptoms. Parastomal hernias that contain bowel and cause obstructive symptoms such as abdominal bloating and vomiting with pain, are the hernias that are most likely to need repairing.

Risk factors

Technical factors and patient factors are responsible for parastomal hernias.

• Technical factors

  Technical factors frequently responsible include the site of stoma placement, size of the trephine, and method of fixation used.

  The size of the trephine is likely to be the most important. A large scientific review found that para-stomal hernias were more common in those people with a trephine greater that 35mm, with a 10% increase in hernia rate for every 1mm increase in size. An analysis of the forces acting upon the trephine that cause dilatation, and ultimately a hernia, show that the larger the trephine radius, the stronger the tangential force pulling the trephine apart, and the greater the risk of herniation. This physical analysis supports the clinical findings that para-stomal hernias are less common following a small bowel stoma (ileostomy) than a large bowel stoma (colostomy).

• Patient factors

  Patient factors that increase the risk of para-stomal herniation include the following:

  1. obesity;
  2. emergency procedure;
  3. weight gain after stoma formation;
  4. poor nutrition;
  5. immunosuppression (including use of steroids and biologics)
  6. emphysema and smokers (chronic cough leads to raised intra-abdominal pressures) and
  7. inflammatory bowel disease (Crohn’s and ulcerative colitis).

Obesity appears to be the stand-out risk factor. Those with a waist circumference of greater than 100cm or BMI >30 are at particular risk. Those having a stoma as part of an emergency procedure are also at increased risk, as poor nutrition, immunosuppression, and large hole (trephine) to accommodate a swollen bowel are all likely to co-exist.

There is growing evidence to suggest that defects in collagen metabolism lead to altered wound repair and increase the risk of hernias.

Prevention of parastomal hernias

The aim of prevention is to minimise both the technical and patient risk factors already described.

Surgery for Stoma Hernias

Surgery for parastomal hernia is required if it is symptomatic, progressively enlarging, or contain bowel being irreducible. Surgical options include repair of the hernia, or reversal or re-siting of the stoma.