What are the immunologic changes associated with abdominal wall hernia mesh?

From the Guidelines

Abdominal wall hernia mesh repairs can trigger immunologic changes in the body, and the choice of mesh material is crucial in minimizing these changes and preventing mesh-related complications. When mesh is implanted, the body initiates an inflammatory response that progresses through several phases. Initially, neutrophils and macrophages infiltrate the area, followed by fibroblasts that begin tissue integration. This foreign body reaction typically leads to fibrous encapsulation of the mesh, which is generally beneficial for mesh incorporation. However, in some patients, chronic inflammation may develop, characterized by persistent macrophage activity, foreign body giant cells, and pro-inflammatory cytokine production. These immunologic changes can manifest clinically as mesh-related complications including seromas, chronic pain, mesh contraction, or mesh rejection. Factors influencing the immune response include mesh material (polypropylene typically elicits stronger reactions than polyester or PTFE), mesh weight (lightweight meshes generally cause less inflammation), coating substances, and individual patient factors like genetics and comorbidities.

Key Considerations

• The use of biological meshes, such as Permacol and Strattice, has been shown to have varying degrees of success in abdominal hernia repair, with some studies indicating a lower recurrence rate at 12 months for cross-linked meshes compared to non-cross-linked meshes 1.
• The choice between a cross-linked and a non-cross-linked biological mesh should be evaluated depending on the defect size and degree of contamination, as recommended by the WSES guidelines for emergency repair of complicated abdominal wall hernias 1.
• Surgeons should consider the immunologic implications of mesh selection, particularly in patients with autoimmune disorders or history of foreign body reactions, and post-operatively monitor for signs of problematic immune responses, such as persistent pain, swelling, or erythema beyond the expected healing period.

Mesh Selection

• The selection of mesh material should be based on the individual patient's needs and the specific characteristics of the hernia, including the size of the defect and the degree of contamination.
• Biological meshes, such as Permacol and Strattice, may be a viable option for patients with contaminated or dirty surgical fields, as they have been shown to have a lower risk of infection and recurrence compared to synthetic meshes in some studies 1.
• However, the use of biological meshes is not without risks, and surgeons should carefully weigh the benefits and risks of each type of mesh before making a decision.

Post-Operative Care

• Post-operatively, patients should be monitored for signs of mesh-related complications, such as seromas, chronic pain, mesh contraction, or mesh rejection.
• Persistent pain, swelling, or erythema beyond the expected healing period may indicate problematic immune responses requiring evaluation and potential intervention.
• The use of negative pressure peritoneal therapy may play a role in mitigating the bio-mediator effects that cause distant organ failure and is an additional potential benefit of an open abdomen in cases of severe complicated intra-abdominal sepsis 1.

From the Research

Abdominal Wall Hernia Mesh Immunologic Changes

• The use of synthetic mesh in abdominal wall hernia repair can lead to immunologic changes, including inflammation and immune response to the mesh material 2.
• Studies have shown that mesh infection after abdominal hernia repair can be a devastating complication, affecting the immune system and requiring prompt treatment 3, 4.
• The development of antibacterial coatings for hernia mesh, such as the PA/PHMG coating, has shown promise in reducing bacterial infection and promoting tissue repair 2.
• Immunohistochemical analysis has revealed a significantly attenuated degree of neutrophil infiltration in the PA/PHMG coating group, attributed to the decreased bacterial numbers alleviating the inflammatory response at the implant sites 2.
• The use of composite mesh has been shown to provide satisfactory results in patients with complicated large ventral hernia, with a trend of low wound complication and recurrence rates 5.

Mesh Infection and Treatment

• Mesh infection after abdominal hernia repair can be treated with conservative management, excision of mesh with primary closure, single-stage reconstruction, immediate staged repair, or repair in contaminated field 4.
• The choice of treatment approach depends on the severity of the infection, the type of mesh used, and the patient's overall health status 3, 4.
• Laparoscopic exploration is an effective and minimally invasive approach to detecting internal organ involvement and removing the infected hernia mesh from affected patients 3.

Mesh Materials and Designs

• Various mesh materials and designs are available, including lightweight materials, meshes with improved attachment, antimicrobial fabrics, composite and hybrid textiles, and performant mesh designs 6.
• The development of new mesh materials and designs aims to improve treatment outcomes, reduce complications, and promote tissue repair 6, 2.
• The use of polypropylene-based composite mesh has been shown to provide satisfactory results in patients with complicated large ventral hernia 5.