CHAPTER 42

ABDOMINAL WALL HERNIAS: EMERGENCIES AND RECONSTRUCTION

TIMOTHY C. FABIAN AND MARTIN A. CROCE

INTRODUCTION

There are few conditions that test the combination of a surgeon’s critical care skills, technical ability, and judgment more than a patient with an open abdomen. Successful management depends on appropriate initial operative intervention, temporary abdominal wall coverage (depending upon the etiology for open abdomen), delivery of surgical critical care, management of complications, and definitive abdominal wall reconstruction (AWR). The current chapter will address these issues. We will discuss acute abdominal wall coverage as it relates to the etiology of the defect and methods for temporary closure. Different options for definitive abdominal wall management will be presented, including technical points for reconstruction. Finally, data regarding outcomes for AWR will be presented.

Acute Coverage: Etiology

Abbreviated Laparotomy for Trauma. The concept of abbreviated laparotomy for critically injured patients was described by Stone et al.¹ in 1983. They described the concept of addressing life threatening hemorrhage quickly followed by immediate closure of the abdomen without definitive management of the hollow organ or other abdominal injuries. Ligation of injured bowel segments to control contamination was recommended. Gauze packing of major hepatic injury or other areas of the abdomen with “nonsurgical bleeding” was used to control hemorrhage. Patients later returned to the operating room when hemodynamically stable for definitive management—bowel resection and anastomoses, ostomy creation, omental packing of hepatic wounds, etc. These investigators demonstrated improved survival in patients who had laparotomy terminated as rapidly as possible to avoid further hemorrhage and its sequelae—particularly coagulopathy. The concept of traumatic coagulopathy was subsequently expanded upon by Moore² who referred to the “bloody vicious cycle” of metabolic acidosis, hypothermia, and progressive coagulopathy. Subsequently, the term “damage control” was introduced by Rotondo et al.³ to describe the abbreviated laparotomy as initially reported by Stone.

While the concept of abbreviated laparotomy undoubtedly has saved numerous lives, it was not without its own problems; we have in some sense traded morbidity for decreased mortality. Some patients had temporary abdominal closure with prosthetic material. Usually, this material was polypropylene mesh. Contact with the underlying bowel sometimes led to fistula formation, especially if the mesh was left long enough to allow ingrowth of granulation tissue.⁴ If the skin was simply closed over the mesh, the mesh frequently became infected.^5–7 Other patients still underwent attempts at abdominal closure, with the hope that abdominal closure would allow the gauze packing to effectively tamponade exsanguinating hemorrhage. The packing was effective, but the increased abdominal pressure led to a series of physiologic perturbations. Profound respiratory failure, renal failure, and subsequent cardiovascular collapse were observed, leading to the recognition of the entity “abdominal compartment syndrome” (ACS).

Abdominal Compartment Syndrome. While compartment syndrome may occur anywhere in the body, it is more likely to develop in anatomic compartments with low compliance.⁸ Common anatomic sites are extremities, the intracranial vault, and the abdomen. Regardless of location, the most likely final common pathway is an ischemia/reperfusion injury (Algorithm 42.1). Endothelial damage from ischemia/injury initiates a series of inflammatory cascades resulting in the loss of endothelial cell tight junctions and subsequent interstitial edema and cellular swelling. Continued ischemia further exacerbates the hyperinflammatory response, resulting in continued ischemia. Reperfusion, with its attendant neutrophil activation and oxygen-free radical production, further accelerates the cellular damage and interstitial edema. This causes dramatic increase in interstitial edema, resulting in alterations in microvascular blood flow. Typically, pressures around 25 mm Hg are necessary for reduction in microvascular flow. Left untreated, this cascade of events usually leads to cellular death in the compartment. It is important to realize that the detrimental edema and microvascular flow alterations require reperfusion; that is, resuscitation from shock. This phenomenon is most evident following revascularization of the lower extremity following vascular injury. If four compartment fasciotomies are performed prior to vascular repair, minimal swelling of the muscle is seen. However, when fasciotomies follow vascular repair, the muscle typically will bulge.

The pathophysiology of the ACS is similar. ACS may be viewed as a global ischemia/reperfusion injury, resulting in significant visceral edema. The three characteristics of ACS are respiratory insufficiency, decreased splanchnic flow, and diminished renal function. In a series of experiments in dogs, Richardson and Trinkle⁹ created a model of progressive intra-abdominal hypertension (IAH). This linear pressure increase resulted in a dramatic increase in peak inspiratory pressures, decreased cardiac output, and venous hypertension in both the inferior vena cava and renal veins; all at an abdominal pressure of 25 mm Hg. These findings were confirmed in a porcine model by Diebel et al.¹⁰ They demonstrated that increased abdominal pressures reduced cardiac output (without alterations in pulmonary artery occlusion pressures), decreased superior mesenteric arterial flow, and decreased mucosal pH.

The three types of ACS are primary, secondary, and recurrent. Primary ACS typically follows injury, shock and resuscitation, and laparotomy (either abbreviated with or without gauze packing); this type is most commonly seen. Secondary ACS is typically seen in patients who receive massive fluid resuscitation following severe injury,¹¹ burns, or resuscitation from sepsis.¹² Secondary ACS was originally described by Maxwell et al.¹¹ in seven patients who developed ACS without previous laparotomy. All patients had dramatic improvement following abdominal decompression. Recurrent ACS (formerly called tertiary ACS) is ACS, which recurs after initial treatment; likely due either to inadequate initial treatment or ongoing tissue ischemia.

In suspected cases with the clinical scenario of ACS, the diagnosis may be confirmed by measurement of the bladder pressure, which reflects abdominal pressure. There are many ways to measure bladder pressure,^13–16 and there are currently commercially available kits that allow continuous measurements. The World Society of the Abdominal Compartment Syndrome (www.wsacs.org) has offered standard definitions of IAH based on the intra-abdominal pressure (IAP) and standard methods of pressure measurement.¹⁷ There are four proposed grades of IAH:

Abdominal perfusion pressure (APP), which is analogous to cerebral perfusion pressure, may also be calculated:

APP = mean arterial pressure – IAP

Some have suggested that the APP is an accurate predictor of abdominal visceral perfusion.^18,19 A target APP of at least 60 mm Hg is associated with improved survival in patients with IAH and ACS.¹⁸ ACS may be defined as sustained IAP > 20 mm Hg (with or without an APP < 60 mm Hg) that is associated with new organ dysfunction.¹⁷ The management of patients with ACS is the same as for patients with compartment syndrome of any other body area; decompression. This, of course, results in a patient with an open abdomen. In less severe cases, nonoperative therapy may be beneficial.^20,21

Severe Intra-abdominal Infection. There are instances when adequate source control may not be possible with a single laparotomy. Diseases such as perforated diverticulitis and necrotizing pancreatitis may result in diffuse suppurative peritonitis. Leaving the abdomen open in such instances allows easier access for repeat laparotomy for irrigation, debridement of nonviable tissue, and ultimately, source control. This practice of repeat laparotomy has not been shown to improve patient outcome in controlled trials.^22,23 Nonetheless, it has its proponents and may be performed in the operating room or at the bedside in the ICU in selected cases.^24–26 More importantly, repeat laparotomy is frequently required to obtain effective source control, and the open abdomen can avoid the development of ACS in these critically ill septic patients.

Mesenteric Ischemia. The management of patients with acute mesenteric ischemia is facilitated by use of the open abdomen. The “second look” procedure allows assessment of bowel viability and resection of ischemic or necrotic segments, if necessary.²⁷ Ward et al.²⁸ demonstrated improved outcome in patients with delayed bowel anastomosis and repeat laparotomy. Park et al. demonstrated improved survival with bowel resection at either the first or second look procedure.²⁹ By leaving the abdomen open, even in the patient deemed low risk for development of ACS, the fascial edges are spared repeat fascial closures and necrotic fascial edges.

Abdominal Wall Loss. Necrotizing soft tissue infections of the abdominal wall are devastating disease processes. Adequate source control requires prompt diagnosis and operative intervention, which may necessitate debridement of large portions of the abdominal wall.^30,31 Interestingly, this problem has decreased in frequency with more liberal uses of the open abdomen. Leaving the abdomen open avoids tight fascial closure. This tight closure may result in strangulation of the fascia, which can serve as a nidus for infection in contaminated wounds.

Other causes of abdominal wall loss include shotgun blasts and high-velocity gunshot wounds. It is imperative to adequately debride these wounds. In the case of shotgun injuries, the shell and wadding are frequently imbedded in the tissue and must be removed. In the case of high velocity injuries, the missile tract should be debrided of nonviable tissue. The kinetic energy imparted to the tissue will cause more extensive injury, and these wounds frequently result in significant tissue loss. These wounds should be reexamined frequently, because they often will require further debridement.

Acute Coverage: Options. The primary goal of acute, temporary coverage of the open abdomen is protection of the underlying viscera. This should be accomplished without compromising the fascia in anticipation of subsequent abdominal closure or reconstruction. Effective temporary closure allows control of fluid losses and helps reduce the catabolism associated with large wounds. To these ends, there are a number of options for temporary closure. The primary options are plastic, absorbable mesh, a vacuum device, skin, and nonabsorbable mesh (Fig. 42.1).

Plastic Closure. One of the easiest devices to use for temporary abdominal closure is a sterile 2-L IV infusion bag. Surgeons in Colombia described its use years ago for temporary abdominal closure; hence the term “Bogotá bag.” Another plastic device for acute coverage is the x-ray cassette cover. These are inexpensive, readily available, and can cover a large area if necessary. Plastic temporary closure is a short-term method for coverage since it is not particularly durable. The plastic is typically sewn to the skin edges allowing for a fairly rapid closure. Another advantage to using plastic for acute coverage is it allows the underlying viscera to be visually inspected. Plastic closure is generally during the first 48–72 hours postinjury as ongoing resuscitation is necessary. If the patient survives this initial phase after injury, a more durable method of temporary abdominal closure will be necessary.

Absorbable Mesh. The use of absorbable mesh for acute coverage affords more durability for temporary closure than does plastic. These meshes, polyglycolic acid (Dexon), and polyglactin 910 (Vicryl) may be sewn to the fascia and will prevent the progressive loss of abdominal domain that may be seen when the closure material is sewn to the skin. The authors’ choice is woven polyglactin 910. It is not as elastic as polyglycolic acid or knitted polyglactin 910, but is similarly pliable. Since it does not stretch, it allows sequential pleating that can facilitate delayed fascial closure. It is important to note that pleating the mesh should be performed frequently to avoid adhesions between the viscera and abdominal wall. If the mesh is placed and no attempts are made to cinch and pleat it, adhesions will form, and the patient is destined for a planned ventral hernia. When the mesh is ready to be removed, it simply peels off the underlying viscera and early granulation tissue since there is a thin suppurative layer that forms under the mesh. In a small number of patients, there is rapid ingrowth of granulation tissue through the mesh. In these patients, skin graft may successfully be performed without attempts at mesh removal.

Vacuum Closure. Use of vacuum-assisted temporary abdominal closure is gaining in popularity due to its rapid placement and simplicity. There are also commercially available kits for vacuum-assisted closure of the abdomen. Since its original description by Brock et al.³² in 1995, it has become one of the standards for acute coverage of the open abdomen. Whether the “homemade” vacuum device³² or the commercial device is used, there are a number of real and theoretic advantages. Perhaps, the most important component is the sheet of plastic that is placed beneath the abdominal wall and superficial to the viscera. This sheet precludes adherence between the viscera and abdominal wall that may facilitate delayed fascial closure. Indeed, several investigators have reported high-delayed fascial closure rates for patients with vacuum-assisted acute coverage ranging from 65% to 100%.^33–35 However, only one prospective randomized study has been performed comparing vacuum with absorbable mesh for acute coverage of the open abdomen. Bee et al.³⁶ randomized 51 patients to either vacuum-assisted or polyglactin 910 coverage for patients with open abdomens.³⁶ There was no difference in delayed fascial closure rates (31% for vacuum and 26% for mesh). The lower delayed fascial closure rates occurred despite strict protocols with aggressive mesh pleating and repeated attempts at closure. It appears that the best predictor for delayed fascial closure is patient selection. It is unlikely that patients with massive visceral edema and hemorrhagic shock will undergo delayed fascial closure. On the other hand, patients without massive edema, or those left open for “second look” procedures, are excellent candidates for delayed closure. Regardless, careful attention to the abdomen with repeated attempts at closure is required to optimize delayed facial closure rates.

Nonabsorbable Mesh. Early materials for temporary abdominal coverage included polypropylene mesh. This mesh was sewn to the fascia, preventing loss of domain. It was either removed when granulation tissue began to grow through the interstices or left in place. If removed, a split-thickness skin graft was placed over the wound. If left in place, full-thickness skin and subcutaneous tissue were typically mobilized and reapproximated. This method had the advantage of eliminating a large ventral hernia. There were two problems with this management; fistula formation and mesh extrusion. Fistula rates around 20% were reported, with progressive mesh extrusion even higher over time.^4,5,37 Since there are better alternatives available, there is little need for polypropylene mesh for acute coverage of the abdomen. Another nonabsorbable option is use of the plastic artificial burr (Wittmann patch). Velcro-type sheets are sutured to the fascial edges and allowed stepwise reapproximation of the fascia. Investigators have reported high-delayed fascial closure rates.³⁸ A modification described by Fantus involves placement of a plastic sheet beneath the abdominal wall, similar to the vacuum device, to prevent adhesions and facilitate closure.³⁹

Skin Closure. In patients with relatively small fascial defects where delayed fascial closure cannot be accomplished, there are basically three options: allow the wound to granulate, place a split-thickness skin graft, or mobilize skin and subcutaneous tissue for approximation. The latter allows a better cosmetic result, but does not change the need for ultimate ventral hernia repair. Split-thickness skin grafting provides optimal coverage for large defects and is a key component in the staged management of AWR as described later. A subset of patients may benefit from immediate skin reapproximation with a series of towel clips or suture. This closure can be beneficial in patients without significant visceral edema and are at low risk for the development of ACS. For example, patients with acute mesenteric ischemia and a “second look” procedure may be ideal candidates for initial towel clip closure.

Complications. Given the fact that patients managed with an open abdomen are critically ill and injured, it is not surprising that complications are not uncommon. Most are related to the wound. Patients who have acute coverage material sewn to the skin may develop skin edge necrosis, a relatively minor problem. For those patients with the material sewn to the fascial edge, development of fascial necrosis may be a more serious issue. Both require debridement back to healthy, viable tissue.

Some patients have a persistent systemic inflammatory state, which precludes adequate mobilization of fluids. This results in persistent visceral edema along with an edematous, nonpliable abdominal wall. Regardless of the method of temporary abdominal closure, these patients will not undergo delayed fascial closure. Adhesions will develop between the viscera and abdominal wall, creating a “frozen abdomen.” When this occurs, it is imperative to obtain biologic coverage of the open, granulating viscera. This is best accomplished with split-thickness skin grafting. Wound coverage will reduce the catabolic demand of the open abdomen⁴⁰ and reduce the incidence of formation of enteroatmospheric fistula.

An enterocutaneous fistula is an epithelialized communication between the gastrointestinal tract and the skin. An enteroatmospheric fistula is a hole in the bowel that is exposed in an open abdomen. Should such a fistula occur before the open abdomen has granulated, the management is resection; this is a rare occurrence and is usually the result of a technical failure. The new anastomosis should be buried beneath viable tissue (loops of bowel or the abdominal wall) so that none of the suture line is exposed. Unfortunately, most of the enteroatmospheric fistulae occur in patients with a frozen abdomen, making reoperation precarious at best.

In a prospective study on temporary abdominal closure, Bee et al.³⁶ noted an increased rate of fistulae in patients managed with vacuum closure. Further analysis identified the subgroup more prone to fistula development; patients with tube jejunostomies, placed either for nutrition or for management of duodenal injury. These fistulae were likely due to the plastic drape, which is effective in preventing adhesion formation. While adhesion prevention is advantageous when trying to gradually close an abdomen, adhesion formation between viscera and the abdominal wall is beneficial when patients have tube enterostomies. It is our current practice to avoid vacuum temporary closure in patients with tube enterostomies.

Prevention, of course, is the best course of action. The longer the granulating abdomen is left open, the greater chance for a fistula.^40,41 Jernigan et al.⁴⁰ demonstrated a significant association between a prolonged open granulating abdomen and fistula formation. In their series of 274 patients initially managed with an open abdomen, 129 patients either survived with an open abdomen or had fascial closure. Ten of these patients developed a fistula and had skin grafting almost 10days later than those without a fistula. Thus, early grafting is important for fistula prevention.

Fischer et al.⁴² evaluated 2,224 patients who had laparotomy for trauma and found 43 patients with fistulae (1.9%). The fistula rate for the 380 patients with an open abdomen was 8.4%; nearly 70% occurred prior to skin grafting. Of note, 37% of the fistulae closed spontaneously. Management of these patients is difficult; control of the enteric output and support of nutrition are paramount. Control may be obtained by various tubes placed in the fistula, but this is rarely completely successful and often enlarges the size of the enterostomy (Fig. 42.2). The bowel is protected, and the sponge is cut around the fistula; this allows output control. Skin grafting may be possible around the fistula so that an ostomy bag may be placed. As long as nutrition can be maintained, these patients can then undergo fistula resection at the time of AWR.

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