From the Guidelines
The immunologic response to mesh hernia repair is a complex process that involves an initial acute inflammatory response, followed by a chronic inflammatory state, and ultimately, the formation of a fibrous capsule around the mesh, with the choice of mesh material and surgical technique playing a crucial role in determining the outcome, as evidenced by a recent multicentre large-sized retrospective study that compared suture, synthetic mesh, and biologic matrix in contaminated ventral hernia repair, which found that a biologic matrix was associated with a non-significant reduction in both SSI and recurrences 1. The use of mesh in hernia repair triggers an immediate acute inflammatory response characterized by neutrophil infiltration, followed by macrophages that attempt to phagocytize the foreign material. Since the mesh cannot be broken down, a chronic inflammatory state develops where macrophages fuse to form foreign body giant cells. These cells release cytokines and growth factors that recruit fibroblasts, which deposit collagen around the mesh, creating a fibrous capsule.
- The encapsulation process is essential for mesh integration but varies based on mesh composition, with polypropylene meshes typically eliciting a stronger inflammatory response than polyester or biologic meshes, as reported in a study by Carbonell et al. that investigated open ventral hernia repairs performed with a polypropylene mesh in the retro-rectus position in clean-contaminated and contaminated fields, which found a 30-day surgical site infection rate of 7.1 and 19.0%, respectively 1.
- Patients with heightened immune responses may experience mesh rejection, chronic pain, or seroma formation, highlighting the importance of careful patient selection and surgical technique, as emphasized in a study by De Simone et al. that included 71 patients who underwent emergency ventral hernia repair with a biological mesh, which found that high ASA score, smoking, diabetes, chronic immunosuppression, previous hernia repair, and dirty surgical field were associated with wound complications 1.
- To minimize adverse reactions, surgeons often select lightweight meshes with larger pores that allow better tissue ingrowth and use minimally invasive techniques, as recommended in the 2017 update of the WSES guidelines for emergency repair of complicated abdominal wall hernias, which suggests that primary repair is recommended when the size of the defect is small, and a biological mesh may be used for repair in contaminated fields 1.
- Post-operatively, patients should monitor for signs of excessive inflammation, including persistent pain, redness, or drainage, and while no specific medications are routinely prescribed to modulate the immune response to mesh, non-steroidal anti-inflammatory drugs may help manage post-operative inflammation, as suggested in a study by Han et al. that included 63 patients who underwent emergency surgery for acute incarcerated abdominal wall hernias with human acellular dermal matrix repair, which found a low rate of infection and recurrences 1.
From the Research
Immunologic Response to Mesh Hernia Repair
- The immunologic response to mesh hernia repair is a crucial aspect of the healing process, and various studies have investigated the differences between biologic and synthetic mesh in terms of postoperative outcomes 2, 3.
- A systematic review and meta-analysis of randomized controlled trials comparing biologic and synthetic mesh in elective open ventral hernia repair found that biologic meshes resulted in increased hernia recurrences and surgical site infections compared to synthetic mesh 2.
- Another study, a pilot randomized controlled trial, compared synthetic and biologic mesh for complex open ventral hernia repair and found that biologic mesh demonstrated no benefit compared to synthetic mesh in one-year outcomes, with a higher percentage of major complications, surgical site infections, and wound dehiscence 3.
- In contrast, studies on inguinal hernia repair have shown that lightweight mesh may be preferable to heavyweight mesh in terms of reducing chronic pain and foreign body sensation, without increasing the risk of recurrence 4, 5.
- The use of mesh in hernia repair has been shown to reduce the risk of recurrence compared to tissue repair, and newer mesh products, such as lightweight meshes, are being developed to improve outcomes and minimize complications 6.
Key Findings
- Biologic meshes may have a higher risk of complications, such as hernia recurrence and surgical site infections, compared to synthetic mesh 2, 3.
- Lightweight mesh may be preferable to heavyweight mesh in inguinal hernia repair, with reduced chronic pain and foreign body sensation 4, 5.
- The choice of mesh material and type should be based on individual patient factors and the specific hernia repair procedure being performed 2, 3, 4, 5, 6.