In Brief

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Abdominal wall hernia (AWH) is 1 of the most common abnormalities encountered by gastrointestinal surgeons. Although the true incidence is unknown, the National Center for Health Statistics estimates that approximately 5 million Americans have an AWH. Because inguinal herniation has been recently addressed by this journal, we review here other abdominal wall hernias. To illustrate the significance of these hernias, 360,000 noninguinal abdominal wall hernias were repaired in 2003 alone.

Abdominal wall hernias can be small and relatively asymptomatic; however, most do cause patients pain and discomfort and affect their quality of life. Furthermore, a small proportion of these hernias progress to incarceration and even strangulation of bowel and other viscera, both of which can be life-threatening. Considering also the fact that as many as 1 in 5 patients who undergo a laparotomy will develop an incisional hernia, it is clear that abdominal wall hernias remain a common and costly health care issue in this country.

Positive developments on the approach to and treatment of AWH over the past several years can be reported. Of all recent developments in ventral herniorrhaphy, 2 bear special mention. The surgical shift over the past 10 to 15 years from primary suture repair (initially under tension) to tension-free repair requiring placement of a biomaterial mesh is regarded as a very important trend in herniorrhaphy.

A second, more recent advance is the advent of a minimally invasive or laparoscopic approach to ventral hernia repair. First described in the early 1990s, it is a procedure being increasingly adopted by surgeons across the country. The techniques, outcomes, and reported benefits of laparoscopic incisional/ventral hernia (LIVH) repair are considered in detail in this issue.

To summarize the significant impact of both advances, informal industry estimates suggest that approximately 70% of ventral or incisional hernia repairs in the United States are now performed with mesh. Furthermore, 10 years ago laparoscopic techniques were used in less than 1% of all mesh repairs for ventral/incisional hernias whereas 5 years later that figure had risen to 15%. At present 25% to 30% of all mesh repairs of ventral or incisional hernias are performed laparoscopically.

In this issue we also review the most important aspects of abdominal wall anatomy as related to hernia formation and repair. The abdominal wall consists of a complex fusion of overlapping layers of muscle and connective tissue designed to contain and protect the abdominal viscera while facilitating rotation and approximation of the thorax with respect to the pelvis. The complex interaction of these muscles along with the rectus sheath forms an important basis for understanding hernia development and repair.

Equally important to such an understanding is the pathophysiology of the forces involved. Hernias are defined as a defect in an aponeurotic layer, resulting in the protrusion of an organ out of a cavity in which it normally resides. This occurs as a result of increased intra-abdominal pressure that exceeds abdominal wall counterpressure. Pascal’s principle and the law of LaPlace are frequently referenced, but we analyze them here with the specifics of AWH in mind.

An understanding of the biochemical basis for incisional hernia formation remains in its infancy. It has long been speculated that a dysfunction of collagen synthesis or deposition may be a causative factor in clinical herniation. More recent research has been focused on the extracellular matrix as the dynamic scaffolding that allows appropriate tissue remodeling and healing. It is now recognized that there is an active role taken by collagen subtypes as well as fibronectin, laminin, and a host of other glycoproteins. The results of this research suggest that surgical technique clearly alters the body’s tissue response on both a molecular as well as a functional level.

A myriad of factors has been associated with incisional ventral hernia formation and recurrence. Unfortunately, strong literature that supports the significance of individual risk factors is lacking. We consider the contributing factors in 2 categories: those that are patient-related and those that depend on surgical technique. Most comorbidities, however, do not seem to have a substantial impact on incisional hernia recurrence.

Despite the large number of ventral hernias repaired in the United States annually, there is no clear consensus about the best method of treatment. The rationale for elective repair of ventral and incisional hernias relates to the risk of incarceration of the hernia and resulting strangulation of the herniated intestine. The true incidence of incarceration is unknown, but it may occur in as many as 10% of all ventral hernias.

Primary repair has been reserved typically for ventral hernias smaller than 4 cm in their greatest dimension. Since primary closure of even small incisional hernias has been associated with long-term recurrence rates between 40% and 60%, most surgeons have abandoned this technique.

Prosthetic materials may be used to repair ventral hernias in a tension-free manner. Numerous techniques used commonly in such repairs include mesh overlay, mesh inlay, properitoneal underlay, and intraperitoneal underlay. Repairs differ in type, location, and fixation of prosthetic material. Despite such differences, each of these tension-free repairs serves to bridge the hernia defect with the prosthetic material widely overlapping normal healthy tissues. This allows the defect to be repaired without increasing intra-abdominal pressure, which is known to stress the integrity of the hernia repair. Tension-free hernia repairs are associated with recurrence rates that are significantly lower than the recurrence incidence in primary repairs.

In ventral hernia repair the use of prosthetic materials has resulted in decreased incidence of recurrence; however, these implants are not without potential for side effects and complications. These materials best act to provide a permanent abdominal wall repair that does not result in adhesion formation and is compliant, strong, durable, and infection resistant.

Polypropylene, polyester, and polytetrafluoroethylene (PTFE) meshes are the most commonly used hernia prosthetic materials. Innovative bilayer prosthetic materials, most often created with polypropylene and PTFE, may be used in ventral hernia repair. Bilayer prosthetic materials with an absorbable adhesion barrier may also be used. Xenografts that are bioabsorbable tissue scaffolds derived from the extracellular matrix of porcine small intestinal mucosa have recently been used for the repair of incisional hernias. In addition, allografts composed of decellularized human dermis may be useful in contaminated or infected fields.

Numerous materials for prosthetic fixation, including sutures, tacking devices, and fibrin glues, are available to the surgeon. Suturing remains the most common method of prosthetic fixation for ventral hernia repair.