The term hernia is used to describe a weakness or defect of the abdominal wall, through which abdominal contents can protrude. It is important to note the distinction between the hernia defect and hernia contents, as surgical repair is generally more concerned with the former, with a few exceptions. Abdominal wall defects arise at areas of weakness in the abdominal wall. These areas include sites of previous surgery, the umbilicus, as well as areas of weakened abdominal and/or flank musculature such as in lumbar hernias.¹

Patients may unknowingly have an abdominal wall or fascial defect that only becomes apparent after intraabdominal or preperitoneal contents pass through the hernia defect. This is especially true of umbilical hernias, which are the most common type of ventral abdominal hernia.²

The umbilicus is a natural area of weakness in the anterior abdominal wall. Located in the linea alba, it is technically a scar, located at the point of passage of the umbilical vessels through the abdominal wall while in utero. The fascial edges of the hernia develop by the third week of gestation, with the umbilical cord developing by week five. The extra-abdominal rotation of the intestine occurs between the sixth and tenth weeks of gestation, with fascial defect fusing thereafter. A hernia occurs after this area fails to close or later stretches and reopens as an adult. These hernias have been documented as early as the ancient Egyptians, with the first known repair occurring in the first century AD by Celsus. The first series of primary suture repairs were reported by Mayo in 1901,³ a technique that largely remains consistent today for small defects.

Incidence

A wide estimated range of neonatal incidence exists for umbilical hernias. In Caucasian babies, the reported incidence is 10% to 30%. For unknown reasons, the incidence in African-American children is higher. Prematurity and family history of umbilical hernia are known risk factors.

The vast majority of congenital umbilical defects close as infants grow into early childhood. In fact, once children are entering school age, only about 10% of previously diagnosed defects remain on physical exam. For this reason, most pediatric surgeons recommend deferring repair for uncomplicated umbilical defects. The current recommended age for surgical repair in the pediatric literature is at least 2 to 3 years, with many surgeons advocating for even later.

Umbilical hernias diagnosed in adulthood tend to be acquired in nature, and therefore it is more difficult to establish a true incidence. A female predominance exists, with a female:male ratio of 3:1. Also, medical comorbidities or physiologic factors that increase intraabdominal pressure confer a higher incidence of umbilical hernia.² These include pregnancy, obesity, abdominal ascites, chronic obstructive pulmonary disease, or persistent bowel distension or obstruction. In the adult patient, hernia formation seems to be the result of repeated stress on an already vulnerable area.

Clinical Manifestations

An umbilical hernia is typically not difficult to diagnose, and the list of differential diagnoses is short. On physical exam, the practitioner will appreciate a soft mass overlying or adjacent to the umbilicus. Most hernias are reducible and contain only preperitoneal fat or omentum, although some may contain bowel, and caution should be exercised when attempting reduction. In most cases, the fascial defect can be palpated and the defect size estimated. While uncommon, other conditions at the umbilicus may mimic a hernia; an abdominal wall varix, granuloma, or peritoneal tumor implant (Sister Mary Joseph’s nodule) all can be misdiagnosed as an umbilical hernia.

Most umbilical defects do not warrant surgical repair since the majority are small and asymptomatic. However, if the defect is causing discomfort, increasing in size, obstructing bowel, or compromising the overlying skin, surgery is indicated. Many patients will request repair upon hearing they have a previously unknown hernia; in these cases, the patient should be counseled appropriately by an experienced surgeon.

Umbilical hernias secondary to chronic liver failure and ascites represent a special circumstance. First, any Childs classification confers a higher risk of postoperative mortality and morbidity. Second, in this patient population, the risk of hernia recurrence is significantly elevated.⁴ Furthermore, the risk of prosthetic mesh infection, if used, is higher. For these reasons, surgical repair in these patients should be reserved for cases of acute incarceration or progressively symptomatic hernias. These patients should have an explanation of the full spectrum of surgical risk prior to deciding on a treatment.

Treatment

In the patient with a small umbilical hernia, a short curvilinear incision is made just inferior to the umbilicus. Dissection is carried through the subcutaneous tissues and down to the fascial level. The neck of the sac is then encircled with a hemostat. After the sac is dissected free of its umbilical skin attachments, it can be reduced or inverted completely into the peritoneal cavity or incised to explore the contents of the hernia sac. In this way, the redundant portion of the sac can be excised using electrocautery. The fascial defect is then closed transversely with interrupted sutures in an interrupted, figure-of-eight, or horizontal mattress fashion. The skin of the umbilicus is tacked to the fascia layer using a single absorbable suture. This operation is usually performed under local, local with sedation, or general anesthesia depending on patient factors and the size/morphology of the defect. The traditional “vest-over-pants” technique originated by Mayo³ is less commonly utilized since overlapping fascial closures have been shown to weaken the overall wound strength in hernia repair.

In large defects where fascial reapproximation results in significant tension, a prosthetic mesh may be used.⁶ Mesh cones were used in the past but are generally not recommended currently due to risk of migration and recurrent hernia. Composite meshes that are made with protective bioabsorbable layers allow for the mesh to be placed as an underlay in the peritoneal cavity with significant, usually 4 to 5 cm, fascial overlap in all directions. An overlay mesh with uncoated synthetic mesh is also an option to help reinforce the fascial closure. The techniques utilizing prosthetic mesh, including retrorectus and preperitoneal mesh placement, are described in more detail later in the chapter.⁵

Incidence

Incisional hernias have been reported in 10% to 20% of patients following laparotomy, with at least one-third of these patients presenting 5 to 10 years postoperatively. It is estimated that over 100,000 incisional hernia repairs are performed in the United States alone.^7–10 Unsurprisingly, the rate of incisional hernias is lower following minimally invasive surgeries. Recent data have suggested the means of fascial closure following laparotomy greatly influences the rate of incisional hernia repair, with the traditional “1 cm bite, 1 cm travel” producing higher levels of tissue ischemia than a “small, frequent bite” technique. This technique also limits the degree of fascial disruption during normal patient motion. Transverse laparotomies, although rarely performed in the adult population, may also protect against incisional hernia, possibly due to the two-layer fascial closure and the robust vascularity of the rectus muscles.^11,12

Multiple risk factors for incisional hernia have been identified, including obesity, wound infection, diabetes, smoking, immunosuppression medication, ascites, advanced age, and poor nutritional status. Many of these factors predispose to an environment of relative ischemia or deficiency in macromolecules necessary for wound healing. Wound infection has the strongest association with a subsequent hernia, and as such, most surgeons advocate for early reopening and drainage of infected surgical wounds to improve healing.^13–16

Normal wound healing produces long-term collagen deposition and remodeling that maintain the strength of the scar. However, the resulting mature scar is only 80% as strong as the native presurgical fascia. Thus, every surgical wound represents an area of relative weakness that can be exacerbated over time with repeated strain.

Clinical Manifestations

Most patients with an incisional hernia will present with a palpable bulge underlying a previous abdominal incision.⁷ The hernia may present with varying degrees of discomfort. Occasionally, the patient may also voice cosmetic concerns as the hernia becomes increasingly protuberant. Some patients may present acutely with an incarcerated hernia or symptoms of a bowel obstruction such as nausea, vomiting, or obstipation. Less commonly, the overlying skin may be subject to an increasing degree of pressure secondary to the hernia, possibly compromising the dermal vascular plexus leading to “paper thin” skin or skin erosion.

On physical examination, the hernia sac should be palpable, and depending on morphology, an attempt should be made to approximate the fascial edges. Examination can be significantly impaired by an obese body habitus. It is especially important to examine the entirety of the abdominal wall, especially along the same incision, to identify other occult defects which are often present.

Extremely large incisional hernias may present with a large proportion (25% or more) of the abdominal viscera within the hernia sac, a condition commonly referred to as “loss of domain.”^17,18 These hernias typically have a fascial defect greater than 10 cm in diameter. Multiple physiologic changes occur in these patients as a result, most notably musculoskeletal, alimentary, and pulmonary dysfunction. The position of the bowel within the hernia sac leads to chronic venous and lymphatic congestion as well as chronic bowel dilation. Over time this leads to bowel thickening, congestion, and dysfunction. The weight of the hernia sac coupled with the disruption of the abdominal core muscles also predisposes to a hyperlordosis of the lumbar spine that can lead to chronic back pain. Lastly, the drop in intraabdominal pressure that results following extra-abdominal migration into the hernia sac alters the normal pulmonary mechanics and physiologic pressures that drive respiration. Many of these patients require intensive pulmonary care.

Treatment

The treatment of ventral hernias has undergone significant changes in the past 20 years, driven by advances in technology, materials, and “rediscovered” surgical techniques such as the classic retrorectus repair popularized by Rives and Stoppa.

MESH SELECTION

Incisional hernias are, by definition, areas of poor fascial healing and weakness. Therefore, for most clean cases, prosthetic mesh is recommended. The material used will ultimately depend on the location of mesh implantation and the degree of possible contamination.¹⁹ For example, synthetic polypropylene should not be used in the peritoneal cavity due to the risk of fistulization or adhesion to the bowel. Also, permanent synthetic mesh, at this time, is not recommended in contaminated cases.

Biologic meshes have been used in contaminated fields as an alternative to synthetic mesh. However, current data show higher rates of wound complications and hernia recurrence with biologic mesh compared to synthetic mesh. Biologic meshes also carry greatly increased material cost. Absorbable mesh, such as Vicryl, is a much cheaper temporary solution in contaminated fields.¹⁹

Synthetic meshes are available in a variety of materials, sizes, and weight. The most commonly used materials are polypropylene, polyester, and ePTFE. Large-pore mesh offers decreased surface area to harbor infection but retains significant strength. Recent data have shown acceptable rates of mesh infection, about 6%, when lightweight, macroporous polypropylene was used in clean-contaminated fields, although this remains controversial. Composite synthetic meshes are also offered with a protective visceral coating that allows safe placement in the peritoneal cavity.^19–21

MESH LOCATION

The various positions for mesh placement are listed in Table 13-1.⁵ The common theme underlying mesh placement is complete defect coverage with wide fascial overlap. Intraperitoneal placement is performed easily but suffers from high rates of mesh migration, and due to decreased tissue ingrowth, higher mesh infection rates. Preperitoneal and retrorectus positioning benefits from the increased vascularity of their respective spaces, as well as decreased fixation requirement, but requires more dissection to perform. Onlay mesh placement requires the elevation of lipocutaneous flaps and has higher rates of surgical site occurences, but has experienced a resurgence in recent years as it is best suited for uncommon hernia sites such as the flank.

Most laparoscopic repairs involve intraperitoneal onlay mesh (IPOM) placement, with good results. However, increasing numbers of surgeons have begun to use minimally invasive techniques to place mesh in the preperitoneal or retrorectus position.