The key in a hernia defect is the disruption of the continuity of the abdominal wall—depending on the etiology of the hernia and the patient’s surgical history, this may be one or many layers of the abdominal wall. In incisional hernias, this often means a midline defect at the site of the previous midline laparotomy incision (FIG 1).

As shown in FIG 2, the abdominal wall lateral to the rectus muscle is intact, and we can clearly see all three layers—the external and internal oblique and the transversus abdominis muscles inserting onto the linea semilunaris. The defect is clearly between the rectus muscles (FIG 2).

Coughing, the Valsalva maneuver, and contraction of the stomach muscles for postural stability all increase intraabdominal pressure. This pressure is normally opposed by the abdominal wall, which is a muscular and elastic organ and can provide inward force to maintain the viscera in their domain.

When one of the portions of the abdominal wall is unable to oppose the intra-abdominal pressure either due to denervation (as in a bulge) or due to discontinuity of the musculature (as in a hernia), the viscera are forced through that portion by the rest of the competent musculature. The abdominal wall functions uniformly as a pressurized cylinder, whereas sizeable hernias and bulges serve to lower intra-abdominal pressure.

The abdominal wall is muscular but also elastic. This has great bearing on the choice of reconstructive technique, in that the reconstructed muscular and fascial components must be able to stretch, so they can absorb and dampen the sharp rises in intra-abdominal pressure that come with coughing, sudden exertion, and Valsalva.

The most successful repairs occur in the most elastic abdomens, whereas a fibrotic, scarred abdominal wall that is unyielding will have more of a tendency for stitches tearing in the postoperative period. A bridging mesh (synthetic or biologic), besides its inherent inability to provide an inward force, is also inelastic and has a compliance mismatch with the intact abdominal wall, leading to a higher rate of dehiscence and suture pull-through, as shown in FIG 3.

A full history and physical exam is performed, with a focus on prior abdominal surgeries and the means of closure. Patients are encouraged to obtain all previous abdominal operative reports. The medical history looking for bowel dysfunction and comorbid conditions such as diabetes, cardiac anomalies, and chronic obstructive pulmonary disease is obtained.

Gestational history is important in order to ascertain if women have had their abdominal walls stretched previously.

History of weight loss, prior abdominal wall sepsis, or peritoneal dialysis is a factor that will either increase or decrease the elasticity of the abdominal muscles.

Examine the abdominal wall with the patient both standing and lying down. Attempt to reduce the hernia to assess the degree of bowel adhesions and the compliance of the abdomen.

Document the scars of previous surgeries. Evaluate rectus diastasis by watching the patient on the descent phase of a sit-up—a maneuver that clearly shows muscle separation in all but the most obese patients.

Evaluate the skin and subcutaneous tissues for scarring, excess, and wounds because this will need to be addressed for optimal closure.

Social history is necessary, as return to work issues and help at home after surgery will need to be planned in advance.

We routinely obtain a CT scan of the abdomen and pelvis using oral contrast to assess the layers of the abdominal wall, any implanted meshes, or biologic materials and measure the size of the defect for all major incisional hernias. If the patient has no kidney issues, we add IV contrast for an optimal study and to obviate the need to explore the abdomen at the time of hernia closure to save dissection time, limit tissue swelling, and avoid possible bowel injury.

The indications for repair of an incisional hernia are local hernia pain, a history of an obstruction, patient discomfort from an inability to raise core intra-abdominal pressure, unsightliness, and the need for intra-abdominal visceral surgery.

Small asymptomatic defects can be observed (so long as the patient is not traveling to an area lacking modern medical care), as the risk of surgery approximates the risk of observation.

For every patient, there should be a comparison of the expected benefits with the magnitude of the procedure required for repair.