Incisional hernia1) Incisional herniae may become apparent during the early months after surgery when there has almost certainly been some deep wound dehiscence in the postoperative period.

2) A poor-quality scar, as a result of a wound infection or faulty closure technique may disrupt later however, and both morbid obesity and chronic cough greatly increase the risk.

3) Easily reducible wide-necked defects may often be ignored.

4) Some form of elasticated support for comfort is often all that a patient wishes, but if repair is planned it is important to decide whether only part of the wound, or the whole wound, needs to be explored.

5) If there is more than one area of herniation it is usually advisable to repair the whole wound.

6) Accurate preoperative skin marking of the extent of the palpable sac and the fascial defect is helpful.

7) Access is via the original scar, and excision of the scarred skin gives a better cosmetic result.

8) The sac is defined and the plane around it followed to identify the defect.

9) Before repair, the edges of the defect must be defined by incising the junction of normal fascia with the attenuated fascial covering of the sac.

10) A shallow peritoneal protrusion from most of a scar need not be opened and to do so unnecessarily merely increases the risk of small bowel injury, and of ileus.

11) Therefore, if the peritoneum can be freed from the under-surface of the abdominal wall it can be left intact, and the fascia repaired over it.

12) A peritoneal sac through a narrow defect should be excised, and the peritoneum should also be opened if there is any concern that a wide-necked sac could be loculated.

13) More often, the peritoneum has to be opened because it cannot be separated from the abdominal wall, but this has the advantage that the surgeon has the opportunity to palpate the under-surface of the adjacent scar for weak areas which need to be repaired at the same operation.

14) If the peritoneum has been opened it may either be closed separately or with the abdominal wall repair.

15) The edges of the abdominal wall defect are excised so that there is a freshly cut edge of healthy tissue for closure.

16) The suture technique used is similar to that for any abdominal wall closure as described above, but particular care must be taken to encompass healthy fascia in the suture bites.

17) A non-absorbable continuous suture is suitable.

18) If the abdominal wall has retracted laterally and there is any tension, then a mesh or other technique should be used.

19) There is also increasing evidence that some form of mesh repair may be the better option, even when the surgeon is confident that satisfactory tension-free apposition of the fascia can be achieved by using a simple suture technique.

20) An on-lay mesh, placed over the closed fascia and secured to it with sutures, is the simplest technique.

21) However, any superficial wound infection is likely to result in a chronic infection in the mesh.

22) Vacuum drainage of the subcutaneous fat to prevent postoperative haematoma collection and prophylactic antibiotics will reduce the incidence of this complication.

23) Frequently the fascial edges of an incisional hernia do not oppose without tension.

24) Several techniques which mobilize the abdominal wall fascia to close large defects have been described. For example, longitudinal incisions may be made through the lateral side of the anterior rectus sheath which is then elevated off the muscle, folded medially and sutured in the midline. A mesh overlay can be used in addition to ensure extra strength to this repair. This is an operation which, although attractive in theory, is disappointingly difficult to execute satisfactorily, especially when there is extensive abdominal scarring. Most surgeons, however, when faced with this problem would use mesh to bridge the defect in the abdominal fascia, as described below.

MESH IN ABDOMINAL WALL REPAIR

1) The development of inert meshes, such as monofilament polypropylene, has greatly simplified the treatment of most difficult herniae.

2) A mesh may be used over or under a simple repair to provide additional strength.

3) The mesh must be placed so that it is in contact with normal tissue for some distance on either side of the closure, and a few sutures are then used to prevent it becoming displaced in the immediate postoperative period. Ultimately, the mesh becomes incorporated into the tissues and adds greatly to the strength of the final scar.

4) Alternatively, a mesh may be used to bridge a defect in the abdominal wall which cannot be closed without unacceptable tension.

5) The defect may be a large hernia, a congenital abnormality, or represent a portion of the abdominal wall lost through trauma, or excised for malignancy.

6) The ideal position for such a mesh is between the closed peritoneum and the abdominal wall, where intra-abdominal pressure pushes it against the muscles and fascia, and the peritoneum separates it from the bowel. This is only possible if the peritoneum can be separated from the overlying muscles and sufficient peritoneum from the sac can be saved to allow peritoneal closure. Unfortunately, this situation is often unattainable and the mesh has to replace both the peritoneum and the fascia of the defect. In this position a mesh may be in direct contact with bowel, if omentum cannot be placed between. Although there are concerns that this might increase the risk of fistula formation and mesh infections, the results of recent studies have suggested that these fears may be unfounded.

7) A mesh should be several centimetres larger than the defect it will replace, as it is only in the areas of overlap that it can be incorporated into tissue and provide any inherent strength.

8) An extraperitoneal or an intraperitoneal mesh first requires four sutures to prevent any rolling of the edges of the mesh.

9) The edges of the fascial defect are then sewn with a continuous non-absorbable suture down onto the top surface of the mesh, with care being taken to prevent injury to any underlying viscus.

10) Any implanted mesh may become infected. The infection is difficult to eradicate as bacteria may be in a protected environment where there is poor antibiotic penetration, and in spaces too small to allow access to neutrophils.

11) Recent advances in mesh material and pore size have improved this problem, but the surgeon should still be very wary of using a mesh in any potentially infective situation, and antibiotic cover is always recommended.

12) A vacuum drain in the subcutaneous fat reduces the risk of a haematoma as a potential culture medium for infection.

13) An infected non-absorbable mesh almost always has to be removed completely.

14) Smooth inert patches of expanded polytetrafluoroethylene (ePTFE), marketed as Gore-Tex, are an alternative to polypropylene meshes.

15) The reduction in fibrosis may decrease bowel complications when the mesh has to be in direct contact with the bowel, but the poor tissue in-growth inevitably results in a weak attachment of the patch to the abdominal wall and a greater risk of recurrence.

16) Compound meshes with an inner layer of ePTFE and an outer layer of polypropylene may have a role.

17) Inert collagen meshes are a recent advance, which can be used in the presence of infection. They can be of great value in bridging a fascial defect left when an infected mesh has had to be removed. However, as this material is extremely expensive, its use is limited to situations where other techniques are inappropriate.