Gregory Ara Dumanian
Presentation
A 55-year-old diabetic smoker with a BMI of 27 kg/m2 is referred 4 months after a ventral hernia repair with mesh because he has persistent drainage along the midline of his incision. His surgery was uneventful apart from a serosal tear that was identified and repaired immediately. One month postoperatively, he developed a seroma that was drained in the office, and since that time he has noted drainage and a small opening along the middle of the incision, requiring the use of dressing changes twice daily (Figure 1). He is otherwise healthy.
FIGURE 1 • A 55-year-old diabetic smoker, 4 months after ventral hernia repair with polypropylene mesh. The midline draining wound has been present for 3 months.
Differential Diagnosis
The differential diagnosis for this patient includes a mesh infection, persistent noninfected seroma, and an enterocutaneous fistula. A distinction should be made between acute and chronic mesh infections. Acute mesh infections are processes with high levels of inflammation, pyogenic bacteria that can invade local tissue, and tissue necrosis. They occur early after a ventral hernia repair and are associated with a stormy postoperative course, reexploration, and prolonged use of antibiotics. The hallmark of chronic mesh infection (colonization) is nonincorporation of the mesh by the soft tissues and fluid collections, but often without the high levels of inflammation in surrounding tissues. Chronic mesh infections are characterized by a more indolent course (>3 months) and associated with persistent fluid collections, drainage, fistula formation, and ultimately mesh extrusion. Both acute and chronic mesh infections will often require mesh excision and reconstruction, but there are subtle differences in the procedure selected for each condition.
Workup
Workup begins with a thorough physical exam, obtaining cultures of the draining fluid, and assessing the patient’s wound characteristics for the quality of the surrounding skin (erythema, extent of tissue loss) as well as the quality of the drainage (color, odor, consistency). The wound should be gently probed to determine if the mesh is exposed. Mesh colonization is easy to diagnose when the mesh can be visualized or palpated. If the mesh cannot be felt, a CT scan is warranted and may reveal a fluid collection in close proximity to the mesh, although this alone is not diagnostic of mesh colonization. Oral contrast will locate a fistula if present. Fluid around a colonized foreign body does not necessarily enhance, and therefore IV contrast is not always necessary. Secondary signs of infection including pain, erythema, and a leukocytosis can help distinguish between mesh colonization and persistent noninfected seromas. Sampling of the fluid under radiographic guidance can be helpful in differentiating a sterile seroma from an infection. However, low-grade mesh colonization in patients on suppressive antibiotics may not grow any bacteria.
In our case, polypropylene mesh could be palpated at the base of the wound, which tracks into a large cavity. The surrounding tissues are inflamed and woody over an area of approximately 5 × 8 cm. The drainage is yellow-green tinted, approximately 20 mL per day. His WBC is 13,000 per µL, and blood glucose is 300 mmol/L. The patient is otherwise in good health. A CT scan reveals a fluid collection anterior to the abdominal wall overlying the permanent mesh (Figure 2). There are no fistulae visualized. The fluid is drained under radiographic guidance and the culture shows Staphylococcus aureus.
FIGURE 2 • A CT scan reveals a fluid collection anterior to the abdominal wall overlying the permanent mesh.
Diagnosis and Treatment
The most likely diagnosis for the patient in this scenario is chronic mesh colonization. Patients with chronically infected abdominal wall mesh are best thought of as wound problems. The wounds will resolve when the foreign material is removed. While antibiotics alone on occasion can solve a mesh problem, the biofilms present often cannot be penetrated and the bacteria remain present in a dormant state. Before this patient is taken to surgery, the surgeon must (i) anticipate the abdominal wall integrity after mesh removal, which depends on the type of mesh in place and the timing since the last surgery, and (ii) assess the patient’s overall health status and evaluate the quality of the local tissues.
Abdominal Wall Integrity
The surgeon must anticipate whether or not the mesh can be excised without putting the patient at risk for an evisceration. If the mesh can be excised and scar/granulation tissue is present to hold the bowel within the abdominal cavity, then a wound closure and delayed reconstruction with a plan for hernia repair in the future is the optimal treatment. If removal of the mesh is only possible with a full laparotomy and bowel mobilization, then a one-stage mesh excision and abdominal wall reconstruction is performed. The timing since the last surgery and the type of mesh present will lead the surgeon to one of these two pathways. Within 2 weeks of the initial implantation of the mesh, removal will often necessitate a procedure to prevent evisceration, such as placement of a temporary polyglactin mesh or a bioprosthetic mesh. Both of these materials are not prone to colonization by bacteria like prosthetic mesh. After 3 weeks from implantation, bowel adhesions are typically strong enough to avoid evisceration despite removal of the mesh.
The type of mesh present also dictates what the expected strength of the scar tissue between bowel loops will be after removal of the material. Polytetrafluoroethylene (PTFE) meshes can be removed even 3 weeks after implantation without evisceration, because a fibrous rind develops posterior to the mesh. This rind represents granulated viscera and omentum and has enough structural integrity to prevent a postoperative evisceration after the mesh removal. PTFE meshes are used to decrease the chance of problematic visceral adhesions. Unfortunately, the sheet-like nature of the mesh and the relative lack of tissue ingrowth facilitate the spread of bacteria along the surface of the material when contaminated. While it is theoretically possible to rearrange the soft tissues to provide coverage and help clear infection, this can only be done with early exposures before the development of a bacterial biofilm. In general, all PTFE mesh exposures will require explantation of the mesh and wound closure. The resulting hernia that develops 3 to 6 months later can be treated with a prosthetic mesh in a clean field. Polypropylene or polyester meshes act quite differently than do PTFE meshes, and this is related to the tissue ingrowth that occurs with these materials. If the amount of mesh exposed is small and the majority of mesh appears incorporated, local excision of visible mesh may be performed, but only by an experienced abdominal wall surgeon with great care to avoid a bowel injury. Wound contracture of the soft tissues can then occur with local wound care. Larger pieces of exposed polypropylene or polyester mesh must be removed in their entirety. Unlike PTFE meshes, the adhesions between the polypropylene or polyester mesh and the viscera are such that they cannot be stripped out of their location without a formal laparotomy. An associated procedure to prevent evisceration and restore the abdominal wall then becomes a necessity. It is difficult to predict whether composite meshes (comprising both PTFE as adhesion barriers and polypropylene to aid incorporation) will leave behind enough of a rind to contain the abdominal contents. In these situations, both the surgeon and the patient must be ready for the longer mesh dissection and full abdominal wall reconstruction.
Health Status and Quality of Local Tissues
It is imperative for the surgeon to attempt to optimize this patient’s nutritional parameters, ensuring tight blood glucose control (history of diabetes), encouraging weight loss (BMI of 27 kg/m2) and tobacco cessation. Improving these parameters will reduce but not eliminate his risk of wound-healing problems. In general, the inflamed and stiff tissues of a patient with a mesh infection will not hold sutures well and tend not to heal per primam. For these patients, a radical en bloc excision of the wound and mesh can be performed (Figures 3–5), and the abdominal wall reconstruction performed with noninflamed mobilized lateral tissues (i.e., component separation).
FIGURE 3 • An elliptical incision is marked to encompass the draining wound and surrounding inflamed tissues.
FIGURE 4 • Great care is taken to dissect the polypropylene mesh free from underlying bowel.
FIGURE 5 • Removal of the polypropylene mesh in its entirety.
In our case, the patient is informed of the diagnosis and the need for explant of the mesh with singlestage reconstruction using the component separation technique. The possibility of bowel resection, blood transfusion, wound-healing problems, prolonged hospital stay, and risk of recurrence are explained. An initial incision and drainage in the office is performed to better drain the fluid collection and to temporize the wound until the major procedure is performed. Surgery is scheduled after he has stopped smoking, controlled his blood sugars, and has been cleared by his medical doctor.
Surgical Approach for Mesh Removal and Abdominal Wall Reconstruction
This patient’s polypropylene mesh is colonized and must be removed. As discussed above, colonization of a large portion of this type of mesh requires en bloc removal with entry into the abdomen and dissection of bowel under direct vision. In the operating room, an elliptical incision is made through the soft tissues to encompass the inflamed soft tissues and mesh (Figures 3–5). A dissecting finger is introduced between the mesh and the medial aspect of the rectus muscles, and Bovie electrocautery is used to divide the tissue and to excise en bloc the central inflamed mesh and soft tissues located between the rectus muscles. The omentum and bowel are typically stuck to the undersurface of the mesh. With this inflamed central tissue now elevated out of the abdomen, the viscera are now dissected off the undersurface of the mesh with improved visualization to complete the en bloc resection. Pinpoint fistulas may require a bowel excision and resection (Table 1).
TABLE 1. Key Technical Steps
The component separation technique is chosen for abdominal wall reconstruction for this patient because it will allow for resection of the chronically inflamed tissue in the midline in exchange for healthy well-vascularized lateral tissue. The components separation technique (Figures 6–8) involves dividing the external oblique muscle and fascia from their insertion into the anterior rectus fascia from above the rib cage to near the symphysis pubis to create bilateral myofascial rectus abdominis flaps. Skin vascularity is important in these contaminated wounds. The releases along the semilunar lines can be performed through 6-cm transverse incisions located just inferior to the ribs. This preserves the periumbilical perforators that supply the skin blood flow to the abdominal wall. There is a 20-25% recurrence rate when using the component separation technique in this setting without any supporting mesh. As an alternative to component separation, bioprosthetic mesh alone can be used to restore abdominal wall integrity as a nonvascularized “patch.” However, there must be adequate soft tissue coverage for closure over the bioprosthetic. Unless component separation is performed, the tissue used for closure is the undermined medial skin, which is more prone to breakdown. In addition, the long-term integrity of these bioprosthetic meshes is still under great debate.
FIGURE 6 • Releases of the external oblique muscle and fascia are performed through bilateral transverse 6-cm incisions located at the inferior border of the rib cage (Figure 6A). The external oblique muscle and fascia are then divided under direct vision from above the rib cage to the level of the inguinal ligament (Figure 6B and C).
FIGURE 7 • The medial aspect of the rectus muscles are debrided of any nonviable tissue.
FIGURE 8 • The rectus muscles are brought together easily without tension using 0-polypropylene interrupted sutures.
Chronic Seromas with Mesh Present
Chronic fluid collections that do not appear to be infected can occur in association with abdominal wall mesh. Despite a thorough workup, on occasion it cannot be decided preoperatively whether or not there is mesh colonization. For these patients, intraoperative assessment of mesh incorporation must be made. A completely incorporated mesh without a hernia is probably a chronic seroma that can be treated with excision of the bursal cavity and reclosure without the risks of an intra-abdominal procedure. Mesh with areas of wrinkled or nonincorporation associated with a chronic seroma may be better treated with total mesh excision and abdominal wall reconstruction.
Postoperative Management
After a full laparotomy, mesh excision, and reconstruction, a typical hospital stay is 6 to 7 days. An ileus is expected and usually resolves after 4 days, at which point oral food intake can begin. Binders are useful to help compress the skin down to the abdominal wall, but do not prevent hernia recurrences. Drains between the skin and abdominal wall are left in routinely until drainage is < 30 mL over 24 hours. Long-term antibiotics are not necessary when the mesh has been completely removed and en bloc excisions of inflamed tissue performed. Routine follow-up for wound healing and hernia formation is performed.
Case Conclusion
The patient tolerates the procedure well. He remains in the hospital for 6 days, and is discharged home without antibiotics and tolerating a general diet. He shows no signs of hernia recurrence at 18 months postoperatively.
TAKE HOME POINTS
· Before treatment, knowledge of the previous surgeries is mandatory. The timing since the last surgery and type of mesh in place will influence the surgery sequence.
· Mesh exposures and infections should be treated with mesh removal. Some of these patients will require simultaneous abdominal wall reconstruction, depending on the integrity of the abdominal wall after removal of the mesh.
· PTFE-based meshes can often be removed and the skin closed primarily over drains. Abdominal wall reconstruction is performed at a later time, when the patient is well nourished and the tissues are soft and pliable.
· Infected polypropylene and polyester meshes often will require a one-stage excision and reconstruction given the loss of abdominal wall integrity after mesh removal.
SUGGESTED READINGS
Ko JH, Wang EC, Salvay DM, et al. Abdominal wall reconstruction: lessons learned from 200 “components separation” procedures. Arch Surg. 2009;144(11):1047–1055.
Szczerba SR, Sukkar SM, Dumanian GA. Definitive surgical treatment of infected or exposed mesh. Ann Surg. 2003;237:437–441.