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Management of Abdominal Wall Defects

Management of Abdominal Wall DefectsThe management of the complicated abdominal wall defect can be quite complex. As more and more patients with an increasing number of co-morbidities undergo sophisticated abdominal operations, an increasing number of physicians will have the opportunity to participate in the management of these patients. Moreover, it is clear that a multidisciplinary approach affords the best possible outcome, particularly in those patients whose defect includes gastrointestinal complications such as enterocutaneous fistulas. The purpose of this chapter is to provide a broad discussion of the management of these problems.

Incidence

The incidence of incisional hernia after abdominal wall surgery is at least 10%. In some studies of high risk patients, the occurrence rate is as high as 20%. Repair is commonly unsuccessful, with recurrence rates ranging from 20% to greater than 50%. This obviously represents a substantial management problem for the gastroenterologist and surgeon and their associated patients. Regrettably, a large retrospective population cohort study examining over 10,000 patients demonstrated that there had been no improvement in important measures of adverse outcome in the last several decades in these patients.

Nomenclature

The typical definition of the complex abdominal wall defect would include one or more of the following:

1.    Large sized defect (> 40 cm)

2.    Absence of stable skin coverage

3.    Recurrence

4.    Infected or exposed prosthetic material

5.    Compromised abdominal wall soft tissue secondary to co-morbidities, such as irradiation or corticosteroid dependence

6.    Simultaneous visceral complication (eg, enterocutaneous fistula)

7.    A systemically compromised patient (eg, posttransplant, concurrent malignancy, immunodeficiency disease).

Complex abdominal wall defects can occur both acutely and as a delayed consequence of surgery or injury. Acute defects may be the result of trauma, tumor excision, wound dehiscence and evisceration, necrotizing fasciitis, or some other intra-abdominal catastrophe. The acute complex defect maybe divided into two types: (1) unstable and (2) stable. Those with unstable abdominal contents are those where urgent surgical intervention is typically required for intra-abdominal injury or the acute deterioration of intra-abdominal disease (eg, diverticular abscess). An example of an acute complex defect with stable intra-abdominal contents is necrotizing fasciitis. A detailed discussion of the management of these acute defects is more esoteric to the nonsurgeon and will not be discussed further in this chapter.

Patient Examination

A number of factors become important in the examination of the patient with a chronic abdominal wall defect. The location of the defect and, in particular, its relation to previous chest and abdominal scars is very important whether laparoscopic or open repair is being considered. The latter especially can involve substantial areas of tissue rearrangement and advancement. The presence of previous incisions can have a substantial impact on the blood supply to both the skin and soft tissue and the myofascial components of the abdominal wall. The extent of the fascial defect is also vitally important and is likely best determined by a combination of physical examination and radiographic imaging, particularly computed tomography or magnetic resonance imaging. In the setting of an open wound, cultures of the wound can guide antibiotic use both in the preoperative period and after surgery. In patients who have undergone previous tumor excision within the abdomen or abdominal wall, tissue biopsy within the confines of a complex wound would be important to rule out tumor recurrence.

The overall stability of the skin and soft tissue in the setting of a complex abdominal wall defect can also be classified as stable (type I) or type II, indicating absence or instability of the skin and soft tissue coverage overlying the myofascial defect. As previously discussed, the perfusion of both the soft tissue and the myofascia can have a significant impact on reconstruction, and,

therefore, angiography can be helpful in those patients who have undergone multiple previous procedures or in whom regional or distant tissue flaps are being considered to aid in reconstruction. Finally, an evaluation for the presence of gastrointestinal pathology, including enterocutaneous fistula, inflammatory bowel disease, other inflammatory processes including diverticular disease, or recurrent tumor is vitally important before allowing the patient to enter the operating room. Optimization of these problems and their associated comorbidities, including malnutrition, abscess drainage, and assessment and control of the extent of any underlying gastrointestinal pathology are of the utmost importance both in the short term postoperative outcome and in long term results of abdominal wall reconstruction.

Surgical Techniques

The appropriate technique for abdominal wall reconstruction has been, and continues to be, a major topic of discussion in the surgical literature. Selection for a particular patient will depend on a number of factors, including size of the fascial defect, stability or lack thereof of the skin and soft tissue, the presence or absence of complicating gastrointestinal pathology, the extent of previous abdominal surgery, and surgeon experience and preference. The two most widely discussed issues are the use of laparoscopic techniques or open surgery and the performance of a primary repair versus the use of prosthetic material.

Laparoscopic Techniques

Management of Abdominal Wall DefectsLaparoscopic repair of ventral and incisional hernias continues to be studied and has been demonstrated to be a safe and effective alternative to open surgical techniques. There is, however, no consensus in the surgical literature regarding the minimum or maximum size of the fascial defect for which laparoscopic techniques should be used. Certainly this methodology would be contraindicated in those with unstable soft tissue coverage or complicating gastrointestinal pathology such as enterocutaneous fistulas. Essentially all laparoscopic techniques employ the use of prosthetic material to achieve repair of the abdominal wall defect.

Prosthetic Material

The use of prosthetic materialin open ventral and incisional hernia repair continues to be studied as well. The initial report of the use of mesh in the reconstruction of large abdominal wall defects appeared in the surgical literature in 1903 and described the use of silver wire mesh. Use of this material was abandoned because of a significant degree of erosion into other structures. The use of modern material began in 1959 with the introduction of polypropylene (Marlex) mesh. This material along with polytetrafluoroethylene (Goretex or Teflon) or a composite material of the two represents the majority of prosthetic materials used today. The classic use of these materials is either as an inset patch or as reinforcement of a primary tissue repair of myofascia. Placement of these materials can be done extrafascial or above the fascia, extraperitoneal and subfascial, or intraperitoneal. This too continues to be a much-debated topic. Complications of the use of mesh include separation of the mesh from the fascia, contact injury (eg, adherence to other structures, erosion, and fistula formation), and infection. Autogenous tissue is considered by some to be the ideal material to close complex myofascial defects. The source of the tissue can be regional musculofascial flaps most commonly represented by rectus abdominis advancement, which can be achieved using one of several plastic surgery tissue advancement techniques, or the use of distant flaps, including the tensor fascialata or rectus femoris of the thigh or latissimus dorsi.

Inguinal Hernia

Inguinal hernia, a subset or particular variety of abdominal wall defect, although usually less complicated, is a subject in the ongoing debates of prosthetic material versus primary tissue repair and laparoscopic versus open techniques. In these defects the laparoscopic repair can occur by using a transabdominal preperitoneal approach or a totally extraperitoneal technique, both of which use prosthetic mesh. The most widely accepted current open inguinal hernia technique, the Lichtenstein repair, as described by Amid, also uses prosthetic mesh. The appropriate methodology continues to be debated but likely involves the following two important concepts: (1) surgeon experience and (2) whether the planned procedure represents repair of a recurrence.

Summary

In conclusion durable reconstruction of a complex abdominal wall defect requires a complete evaluation of the defect and optimal preparation of the patient along with thoughtful surgical planning. Certainly a multidisciplinary approach is ideal and more times than not should likely include gastroenterology involvement, particularly in those patients who present with gastrointestinal co-morbidities complicating their abdominal wall defect and its reconstruction.

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