Stoma is the name given to a permanent opening created surgically for an artificial bowel or bladder outlet so that those two organs can continue to function artificially. In other words, a stoma is an artificially produced opening in a hollow organ leading to the body surface.
Parastomal hernias particularly often affect the artificial bowel outlet known as an enterostoma (abdominal opening). The artificial bowel outlet is particularly prone to incisional hernias because it proceeds from strong structures which are additionally exposed to major stresses from the bowel itself and from the abdominal wall and the internal abdominal pressure.
In a parastomal hernia, a prolapse occurs beneath the skin of the stoma loop in the bowel and in some cases to an additional prolapse of other parts of the bowel or parts of the organ known as the greater omentum into the subcutaneous fatty tissue.
It is currently believed that 50% to 80% of patients with an artificial bowel outlet also experience a parastomal hernia. Accordingly, incisional hernias constitute a frequent complication of abdominal surgery.
The symptoms of a parastomal hernia manifest as defects in the abdominal wall and a protrusion near the artificial bowel outlet. The bulge through the hernia sac becomes particularly prominent when pressure inside the abdominal cavity increases, which can happen, for example, when coughing or through abdominal pressure.
Even so, the symptoms can vary greatly and can range from the complete absence of discomfort to restrictions in movements and pain. These occur especially if there are circulatory disorders where parts of the bowel are trapped in the hernial ring. In this case, immediate surgery is essential to alleviate pain and restore vital blood circulation in the bowel.
Parastomal hernias occur mainly after surgery where the tissue and the scar of the stoma opening do not grow together sufficiently and form a firm bond. Also, parastomal hernias are more likely in the presence of general compromised wound healing, wound infections and bleeding. In addition, poor general and nutritional status in the patient, diabetes and overweight plus certain illnesses are all contributory factors in parastomal hernias. Certain medications, for example cortisone, compromised collagen metabolism and long-term smoking favor complications after the creation of an artificial bowel outlet.
The following are examples of some of the general risk factors leading to the emergence of a parastomal hernia:
- the patient's age
- adiposity or overweight
- connective tissue weakness
- abdominal surgery
- healed wound infections or
- steroid therapy applied for example for COPD.
All factors weaken the tissue and so favor the failure of the scar to heal properly after surgery and of the stoma to sit securely in the abdominal wall. In this way, organs can also prolapse from inside the abdomen out into a hernia sac if there is increased internal abdominal pressure.
Today, amongst the causes of a parastomal hernia, it is also accepted that there may be a technical error on the part of the surgeon. Even so, the emergence of a parastomal hernia demonstrates that the surgical technique plays no part in the causation of parastomal hernias. This was also shown in clinical studies to be the case. In most cases of a new stoma placement a secondary hernia occurs. This facts shows in particular that the surgical technique seems to have no significance for the emergence of a parastomal hernia.
Also, the fact that a parastomal hernia can be seen as a special form of incisional hernia confirms the view that tissue weakness and scar instability are responsible for the emergence of parastomal hernias.
In most cases, the existence of a parastomal hernia can be established by external clinical examination. In some cases, the contents of the hernia sac can be detected by thorough palpation. However, for a reliable and precise diagnosis of a parastomal hernia, this should be followed by imaging techniques such as ultrasound or MRT. This can also increase the detection rate of small hernias.
Large parastomal hernias in particular require surgery because the hernial ring and hernia sac are correspondingly large and so may contain a lot of bowel contents. Surgery should entail moving the prolapsed contents of the abdomen back into the abdomen, closing the scar and protecting against any further rupture.
However, a very large hernia sac often creates difficult surgical conditions because the whole contents need to be pushed back into position and kept there. At the same time, the anatomical function of the abdominal wall must be restored, which is difficult in the case of parastomal hernias, because the artificial outlet compromises the role of the abdominal wall as a support and constitutes a weak point.
A very reliable surgical technique for the treatment of parastomal hernias has been shown to be the use of a synthetic mesh to reinforce the hernial ring. This is the most reliable method of reducing the rate of recurrence. There are various different mesh materials which are used for the different surgical techniques to repair parastomal hernias.
In open surgery, light meshes with a wide mesh structure made of polypropylene are used. These are in direct contact with the bowel loops and may cause irritations and fistulas because they are very solid. Also, the meshes must show themselves to be more flexible and more finely textured for use in laparoscopic techniques.
Every mesh used in parastomal hernia surgery has different properties so that different meshes produce different physical reactions in the patient's body. This means that the right type of mesh must be selected for every case of parastomal hernia surgery.
In particular, the high rates of recurrence are the reason why the so-called fascia suture is no longer used for parastomal hernias. Even resiting the stoma in a different location is no longer favored because then a new parastomal hernia can be expected. And because the basic conditions of the tissue and the patient remain the same.
Basically, even if a parastomal hernia has been repaired, the likelihood of another forming is very high. In open surgery, a recurrence rate of up to 50% is assumed. This is because the surgical area is exposed to a major risk of infection. This is unlike the situation with minimally invasive techniques, which are exposed to fewer infection risks, even though ideal outcomes are not always achieved.
In general, patients cannot prevent a parastomal hernia on their own, especially because it is caused by an essential surgical intervention. However, there are now studies which demonstrate the efficacy of using a synthetic mesh as a precautionary measure in stoma surgery. This means that using a mesh may prevent the formation of a parastomal hernia because it strengthens the abdominal wall.
If a patient has a high risk of developing a parastomal hernia, such at risk patients can be given a synthetic mesh during surgery as a precautionary measure to strengthen the abdominal wall. In this way, the patient's abdominal wall is reinforced and the new weak point in the abdominal wall, created through placement of an artificial bowel outlet, is circumvented as well as possible.