Wound infection following repair of abdominal wall hernia

INTRODUCTION — The repair of an abdominal wall hernia is a generally clean procedure with a low risk of infectious complications. However, when wound infections do occur following a hernia repair, they can be associated with hernia recurrence, mesh infections, and systemic complications [1,2].

Abdominal wall hernia repairs can be divided into two broad categories:

●Ventral hernia repair includes incisional, ventral, epigastric, spigelian, peristomal, and umbilical hernias. (See "Overview of abdominal wall hernias in adults".)

●Groin hernia repair includes inguinal and femoral hernias. (See "Classification, clinical features, and diagnosis of inguinal and femoral hernias in adults".)

Risk factors for and strategies to reduce the risk of infection after abdominal wall hernia repair are reviewed here. An overview of antibiotic prophylaxis and other control measures to prevent surgical site infection are discussed elsewhere. (See "Antimicrobial prophylaxis for prevention of surgical site infection in adults" and "Overview of control measures for prevention of surgical site infection in adults".)

EPIDEMIOLOGY AND RISK FACTORS — The risk of infection following hernia repair is influenced by a variety of clinical and operative factors, use of mesh, location of mesh insertion, repair technique, use of drains, and emergency indications for the procedure.

Hernia location — Observational studies suggest that ventral hernia repair has a higher risk of wound infection than inguinal hernia repair, although this depends upon the magnitude of the ventral hernia repair. The reported incidence of a wound infection following inguinal hernia repair ranges from 0 to 6 percent [3-14], while the reported incidence following a ventral hernia repair ranges from 0 to 23 percent [1,15-23].

Clinical and intraoperative factors — Clinical risk factors associated with wound infection following hernia repair include [1,17,24-30]:

●Obesity [31]

●Low serum albumin

●Diabetes

●Immunosuppression (eg, chronic corticosteroids)

●Heart failure

●Smoking

●American Society of Anesthesiologists (ASA) score >3

●Advanced age

●Previous methicillin-resistant Staphylococcus aureus (MRSA) infection (independent of body site)

●Chronic obstructive pulmonary disease (COPD) [32]

Intraoperative risk factors associated with a wound infection following hernia repair include [1]:

●Enterotomy

●Bowel resection

●Emergency procedure

●Prolonged operative time

●Perioperative blood transfusion

●Use of mesh to repair large ventral hernia defects (>10 cm)

Open versus laparoscopic hernia repair — Whether a laparoscopic or open repair of abdominal wall hernias is more appropriate for a specific individual and the complications associated with each technique are reviewed elsewhere. (See "Overview of abdominal wall hernias in adults" and "Overview of treatment for inguinal and femoral hernia in adults".)

The laparoscopic technique is associated with a lower risk of superficial incisional surgical site infection (SSI) for inguinal and ventral hernia repairs compared with the open technique. By contrast, there is no significant difference in the rate of deep incisional SSI necessitating mesh removal [12].

●A systematic review that included 5565 patients found that patients undergoing a laparoscopic inguinal hernia repair had a significantly lower rate of superficial wound infection compared with open repair (odds ratio [OR] 0.45, 95% CI 0.32-0.65) [12]. A 2021 systematic review and network meta-analysis of 35 randomized trials also found significantly reduced wound infection rate in minimally invasive versus open (Lichtenstein) inguinal hernia repair [33].

●A review of eight trials with 526 patients found that laparoscopic ventral hernia repair with mesh was associated with significantly fewer superficial incisional SSIs compared with an open repair (1.5 versus 10.1 percent) [23]. There were fewer deep incisional SSIs reported that required mesh removal with laparoscopic repair (0.7 versus 3.5 percent); however, the difference was not significant.

Mesh-related factors — Infections related to prosthetic mesh, which is an avascular foreign body, are more likely to occur if contamination occurs during or after insertion. The interaction of neutrophils with the foreign body diminishes neutrophil function, which may enhance susceptibility to infection. In animal models, the presence of a foreign body reduces the minimal inoculum of S. aureus required to cause infection by a factor of more than 100,000 to as little as 100 colony-forming units. In addition, it is difficult for the host to eradicate mesh-related infections related to the formation of biofilm [34]. (See 'Microbiology' below.)

In a systematic review that included 2418 patients from six cohort studies, the overall infection rate for mesh hernioplasties was 5 percent [24]. In a retrospective review of 3470 cases of abdominal wall hernia repairs, 2 percent developed mesh infections, most of which (73 percent) required explantation of the mesh [35]. Predictors of mesh infection included steroid or other immunosuppressive drug use, urgent repair, and postoperative surgical site infection; predictors of mesh explantation were polytetrafluoroethylene mesh, onlay mesh position, and associated enterotomy in the same procedure.

Non-mesh versus mesh repairs — There are conflicting data regarding whether the use of mesh during hernia repair definitely results in a greater risk for infection than traditional repair without mesh. The reported risk of wound infection following a primary, non-mesh suture repair ranges from 0 to 6 percent [4-9], while the reported risk of infection following a mesh repair ranges from 0.4 to 14 percent [11,15-17,19-23,36-38].

●A meta-analysis of 20 randomized trials with 5016 patients undergoing inguinal hernia repair found no difference in infection rate between open mesh and open primary repairs (OR 1.24, 95% CI 0.84-1.84) [11]. Virtually all infections were superficial.

●A 2018 Cochrane review of mesh versus non-mesh repair of inguinal and femoral hernias [39] included 25 studies with 6293 participants. Wound infection was found slightly more commonly (2 versus 3 percent) in the mesh repair group (relative risk 1.29, 95% CI 0.89-1.86).

●A review of two randomized trials with 341 patients found that the open suture repair technique for primary and incisional ventral hernias was associated with a lower pooled rate of infection compared with the open mesh repair (0 versus 10 percent) [17,22].

●A meta-analysis of nine randomized trials and observational studies that included 1782 patients reported a pooled SSI rate following primary ventral herniorrhaphy of 7.3 percent for mesh repair (n = 31) and 6.6 percent for suture repair (n = 43), which was not significant [40].

●A randomized trial that included 93 patients comparing mesh or non-mesh repair for umbilical hernias reported increased rates of infection following mesh repair (28 versus 9 percent) [17].

Nonabsorbable versus absorbable mesh — Mesh for hernia repair can be absorbable or nonabsorbable and synthetic or biologic. (See "Open surgical repair of inguinal and femoral hernia in adults", section on 'Mesh for open hernia repair' and "Laparoscopic inguinal and femoral hernia repair in adults", section on 'Mesh for laparoscopic repair' and "Management of ventral hernias".)

Meshes that have been used in contaminated fields include:

●Absorbable

•Synthetic polyglactin-910 mesh (eg, Vicryl, Dexon)

•Biologic (eg, Surgisis – derived from small intestinal submucosa)

●Nonabsorbable synthetic polypropylene mesh (eg, Marlex, Prolene, Parietene [semiabsorbable])

●Biosynthetic – Long-term absorbable (eg, Gore Bio-A)

Factors associated with an increased risk for infection when using synthetic mesh include the type of filament and pore size. Monofilament meshes with large pore sizes (>75 micrometers) are associated with lower risk of infection. Microporous meshes (eg, expanded polytetrafluoroethylene [ePTFE]) with a pore size <10 micrometers allow free passage to bacteria but block neutrophils and macrophages [41].

Biologic meshes may be derived from human (allograft) or animal (xenograft – typically bovine or porcine). The most common tissue used is decellularized dermis, which provides a collagen matrix. The porcine meshes are the most commonly used, and the different products differ in the use of supplemental cross-linking (cross-linked: Permacol and Collamend; non-cross-linked: Strattice, Integen, XCM, and XenMatrix). Data on recurrence rates using both types have been up to 50 percent at three to six years [42]. Biologic meshes do clear bacterial contamination better than synthetic materials; non-cross-linked meshes clear bacteria better than cross-linked biologic meshes [43].

Biosynthetic mesh has been introduced as a potential alternative to biologic mesh in contaminated wounds. These meshes are composed of bioabsorbable polyglycolide-trimethylene carbonate copolymer. Biodegradation, which occurs by hydrolytic and enzymatic pathways, is usually complete within six to seven months. In a study of 104 ventral hernia repairs performed with biosynthetic mesh in a contaminated (77 percent) or clean-contaminated (23 percent) operative field, 8 percent developed a superficial infection that was treated with antibiotics alone, while 10 percent developed a deep incisional infection that required drainage, minor debridement, or partial mesh debridement [44].

In general, a permanent synthetic mesh is the most common mesh used, but the use of biomaterials is rapidly expanding [1,10,45-49]. Absorbable mesh and biologic repair materials have been generally preferred in patients with a higher risk of infection (eg, due to comorbid conditions or contaminated/infected surgical fields) since permanent synthetic mesh can complicate treatment of mesh infections (due to the need for mesh removal) [50].

●A multicenter review of 1500 ventral hernia repairs found more infections to be associated with absorbable mesh than with nonabsorbable mesh (22 versus 4 percent). However, this observation was confounded by the higher rate of absorbable mesh use in higher-risk operative settings such as emergency procedure, field contamination (enterotomy, bowel resection, and strangulation), concomitant procedures, and preoperative wound infection or sepsis [1].

●A retrospective review of 541 contaminated ventral hernia repairs found a lower incidence of SSI associated with permanent mesh than with absorbable or biologic mesh (14.2 versus 32.7 and 36.8 percent; p = 0.001). In addition, the permanent mesh repairs had a twofold lower recurrence rate [51]. In this study, 97 percent of the meshes were extraperitoneal.

Location of mesh placement — Location of mesh may or may not impact the risk of wound infection depending upon the type of hernia that is being repaired:

●For inguinal and femoral hernia repair, the mesh can be placed above the fascia (eg, Lichtenstein repair) or below in a preperitoneal position (eg, laparoscopic transabdominal preperitoneal hernia repair [TAPP] or totally extraperitoneal hernia repair [TEP]; preperitoneal, open repair). A randomized trial that compared outcomes for mesh placed above or below the fascia found no difference in rates of SSI [52]. (See "Laparoscopic inguinal and femoral hernia repair in adults" and "Open surgical repair of inguinal and femoral hernia in adults" and "Overview of treatment for inguinal and femoral hernia in adults", section on 'Treatment options'.)

●For ventral hernias, the mesh can be placed above the fascia (onlay technique), below the fascia and muscular layers but above the peritoneum (sublay technique), or directly beneath the peritoneum (intraperitoneal or underlay) (figure 1). A systemic review and network analysis of studies on mesh ventral hernia repairs evaluated the risk of recurrence and SSI based on mesh position. The sublay mesh position had the lowest risk of infection, and the underlay position had the second lowest risk [53]. (See "Management of ventral hernias".)

Complicated hernia repair — For complicated hernia repairs involving acute incarceration and/or bowel resection without gross soilage, many studies support the use of mesh in both groin and ventral locations [54-60]. In 2017, an update of the World Society of Emergency Surgery guidelines for emergency hernia repair recommended [61]:

●Use of prosthetic mesh in the setting of acute incarceration and/or bowel resection without gross spillage. Such practice was not associated with any increase in 30 day wound-related morbidity.

●Primary repair of hernias in the setting of bowel necrosis, gross enteric spillage, or peritonitis. If primary suture repair is not feasible, a biologic mesh may be used for repair.

Placement of drains — The use of drains following a hernia repair is controversial. A retrospective review of 250 patients undergoing ventral hernia repairs with or without mesh found a significantly increased risk of wound infections with drains compared with repairs without drains (19 versus 10 percent) [27]. Nevertheless, drains may be appropriate if there is a large amount of dead space to limit seroma and hematoma formation. The use of drains, where appropriate, is discussed in separate procedure topics.

CLINICAL FEATURES AND DIAGNOSIS — The diagnosis of wound infection is clinical with typical symptoms of localized erythema and pain at the incision site. Purulent wound drainage and separation of the wound may also occur. Other findings on physical examination may include tenderness to touch, warmth, or localized swelling. Patients may have systemic manifestations such as fever, chills, and malaise in addition to local signs of infection [62-64]. Patient with mesh infection can have an indolent course with scarring, abscess, and sinus tract formation.

Compared with superficial incisional surgical site infections (SSIs) not associated with mesh, infections that involve prosthetic material (ie, mesh for hernia repair) typically have a delayed onset [65]. In one case series of 22 patients with mesh infection, only five presented within one month of herniorrhaphy [65].

Diagnosis of postoperative wound infection — Existing definitions of postoperative incisional infections are the usual criteria used by clinicians and investigators to diagnose SSI.

SSI is defined as infection related to an operative procedure that occurs at or near the surgical incision (superficial or deep incisional, or organ/space) within 30 days of the procedure, or within 90 days if prosthetic material is implanted at surgery (table 1). (See "Antimicrobial prophylaxis for prevention of surgical site infection in adults".)

Clinical criteria for defining SSI include one or more of the following [66]:

●A purulent exudate draining from a surgical site

●A positive fluid culture obtained from a surgical site that was closed primarily

●The surgeon's diagnosis of infection

●A surgical site that requires reopening

Although the diagnosis of wound/mesh infection is predominantly clinical, imaging studies such as ultrasound or computed tomography (CT) can be useful to identify fluid collections (seroma, hematoma, abscess) or edema with stranding of the subcutaneous fat around the mesh.

Wound/fluid cultures — In patients with clinical features of wound infection, wound cultures should be obtained to help guide antibiotic therapy, keeping in mind that wound infection is a clinical diagnosis and wound cultures should not be used as a substitute for clinical judgment to determine the need for debridement. (See "Clinical assessment of chronic wounds", section on 'Wound assessment'.)

To obtain fluid for culture, percutaneous drainage can be attempted in patients with wound infection who do not have systemic signs. The results of percutaneous sampling need to be interpreted with caution. It is possible to interpret the results of a culture as significant when it is actually due to contamination.

Fluid collections that are not associated with signs of infection (ie, erythema, warmth, drainage) should generally not be aspirated, due to risk of introducing infection into a sterile site [67].

Microbiology — The bacteria typically implicated in mesh infections are those with the capacity to form biofilm, such as coagulase-negative staphylococci, S. aureus, and enteric gram-negative bacilli. Anaerobes are also potential pathogens [62]. Rarely, mesh infections can be caused by Candida or mycobacteria [68,69].

Biofilms consist of bacterial colonies surrounded by and embedded in exopolysaccharides (also known as glycocalyx) [70,71]. Bacteria within biofilms form complex communities with bacterial communication and adaptation via quorum sensing, which regulates biofilm formation [72]. Bacteria near the surface of the biofilm are usually relatively more metabolically active via their access to nutrients that diffuse through the upper surface of the biofilm; bacteria deep within the biofilm are usually less metabolically active or in various stages of dormancy. Bacteria within biofilms are protected from host defenses such as phagocytes and, often, to antimicrobial penetration.

DIFFERENTIAL DIAGNOSIS — The differential diagnosis of wound infection following hernia repair includes allergies to skin preparation materials or adhesives, seroma or hematoma, foreign body reactions to the mesh materials, post-herniorrhaphy neuralgia, necrotizing fasciitis, and gastrointestinal fistula.

Allergic skin reactions typically occur in the immediate postoperative period and are self-limiting with removal of the offending agent. (See "Common allergens in allergic contact dermatitis" and "Overview of control measures for prevention of surgical site infection in adults", section on 'Skin antisepsis'.)

Fluid collections such as seromas, or hematomas occurring in the early postoperative period, can cause wound swelling but are not associated with signs of infection (ie, erythema, warmth, drainage). These should generally not be aspirated, due to the risk of introducing infection into a sterile site [67]. (See 'Treatment' below.)

A severe foreign body reaction may initially be difficult to distinguish from a wound infection as the clinical features may include erythema and pain; however, no fluid accumulation or drainage will be evident. Significant pain without other signs of wound infection can also occur with nerve injury. (See "Post-herniorrhaphy groin pain", section on 'Differential diagnosis'.)

Necrotizing fasciitis is a serious form of wound infection that can be lethal and is a surgical emergency. It is characterized by a copious, dishwater-like drainage; dusky and friable subcutaneous tissue; and pale, devitalized fascia. (See "Necrotizing soft tissue infections".)

Injury to the bowel during the course of hernia repair may lead to enterocutaneous fistula. Drainage of succus entericus or grossly feculent material makes the distinction, though it may require opening of the wound to make this determination. (See "Enterocutaneous and enteroatmospheric fistulas".)

TREATMENT — The management of wound infection following repair of abdominal wall hernia repair includes aggressive antibiotic therapy, wound drainage, and aggressive wound debridement when appropriate. Specific wound management thereafter depends on the location and nature of the hernia repair.

If there are no systemic signs of infection, culture data should be obtained before starting broad-spectrum parenteral antibiotics listed in the table (table 2). When available, culture findings guide changes in antibiotic therapy. (See 'Wound/fluid cultures' above.)

Superficial incisional surgical site infection — With aggressive treatment, most superficial incisional surgical site infections (SSIs) can be successfully managed without the need to remove the mesh [73]. Providing drainage of the wound may require opening the skin incision, but localized fluid collections may be amenable to percutaneous aspiration.

Symptoms of infection should improve after a few days of antibiotic treatment, which should be continued for 10 to 14 days or until the clinical signs of active infection have resolved. Thereafter, the patient should be monitored closely for signs of recurrent infection. Oral antibiotics may be used to complete therapy in patients who improve quickly and can tolerate oral therapy.

If signs of superficial incisional SSI do not improve with antibiotic therapy, a deep incisional SSI may be present, and surgical incision and drainage with debridement of infected and/or necrotic tissue may be necessary.

Deep incisional surgical site/mesh infection — After initiating empiric antibiotic therapy (table 2), patients who present with systemic symptoms and signs of wound infection should be taken for immediate surgical debridement to remove infected and/or necrotic tissue and to remove the mesh, if present. Debrided material should be sent for aerobic and anaerobic culture and susceptibility results used to tailor the choice of antibiotic therapy. (See "Necrotizing soft tissue infections".)

For patients without systemic signs, percutaneous drainage of any fluid collections can be attempted. In a retrospective study that evaluated outcomes in 21 patients who underwent percutaneous drainage for mesh-related fluid collections, 12 patients (57 percent) were successfully treated with percutaneous drainage and antibiotics [74]. In this study, fluid cultures were positive in 68 percent of patients (n = 13); S. aureus was the most common organism. However, the pathogen did not predict the need for mesh excision.

If symptoms persist following wound drainage and one week of appropriate antibiotic therapy, all foreign material, including mesh, sutures, and staples (as well as necrotic tissue), should be removed when technically feasible [75,76]. Where mesh is well incorporated, whether or not to remove part of or all of the mesh is a matter of clinical judgment. One study reported successful treatment of limited mesh infections (defined as evidence of good incorporation of some of the mesh into surrounding tissue) with surgical debridement, partial excision of mesh, drain placement, and negative pressure wound therapy [77]. However, for mesh infections with no incorporation of mesh into the surrounding tissues, they performed complete excision of the mesh and debridement of the surrounding tissues. An algorithm for managing mesh infections has been proposed [32].

The approach to mesh removal can be tailored to match the hernioplasty method, with open mesh removal performed for open repair and laparoscopic removal for mesh placed minimally invasively [78].

Antibiotics tailored to fluid/tissue culture results should be administered for at least two weeks following removal of foreign material. If symptoms of infection recur following removal of foreign material, incomplete removal with retention of mesh components should be suspected, and repeat debridement should be undertaken.

Graft removal can lead to hernia recurrence; thus, if possible, the infection should be fully eradicated before repeat hernia repair is performed. Some surgeons favor percutaneous sampling of the operative area under sterile conditions to ensure there are no residual bacteria prior to repeat hernia repair [79]. If such cultures are positive, an additional two weeks of antibiotics should be administered, followed by repeat aspiration. Patients with persistently positive aspirates should undergo repeat debridement, followed by additional antibiotic therapy. When needed, methods are available to repair inguinal hernia without the use of mesh and are discussed elsewhere. (See "Open surgical repair of inguinal and femoral hernia in adults", section on 'Nonmesh repairs'.)

Although there are case reports of successful treatment of mesh infections with systemic antibiotics combined with local antibiotic infusion [80-83], in the absence of well-designed trials evaluating the effectiveness of this strategy, we do not recommend these approaches, except possibly as salvage therapy if mesh removal is not possible.

MEASURES TO PREVENT RECURRENT INFECTION — General measures to prevent a surgical site infection (SSI) following hernia repair are the same as for the prevention of infection at other surgical sites. (See "Antimicrobial prophylaxis for prevention of surgical site infection in adults" and "Overview of treatment for inguinal and femoral hernia in adults", section on 'Antibiotic prophylaxis'.)

Alternative methods for providing prophylaxis against surgical site infection (in addition to standard intravenous administration of antibiotics) include antibiotic-impregnated sponges and antimicrobial mesh materials. The effectiveness of these methods for reducing mesh infection with hernia repairs is unproven. (See "Overview of control measures for prevention of surgical site infection in adults".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Ventral hernia".)

SUMMARY AND RECOMMENDATIONS

●Although wound infections following hernia repair are uncommon, occurring in approximately 5 percent of patients, when they do occur, they increase the risk for hernia recurrence. (See 'Epidemiology and risk factors' above.)

●Factors that increase the risk of wound infection following hernia repair include patient-related and technical factors such as obesity, diabetes, smoking, previous methicillin-resistant Staphylococcus aureus (MRSA) infection, enterotomy, bowel resection, and emergency procedure. The laparoscopic technique is associated with a lower risk of superficial incisional surgical site infection (SSI) for groin and ventral hernia repairs compared with the open technique; however, there is no significant difference in the rate of deep incisional SSI necessitating mesh removal. There are conflicting data regarding whether the use of mesh during hernia repair imparts greater risk for infection than repair without mesh. (See 'Epidemiology and risk factors' above and 'Open versus laparoscopic hernia repair' above and 'Mesh-related factors' above.)

●The diagnosis of wound infection is clinical with typical symptoms of localized erythema and pain at the incision site, wound drainage, or separation of the wound edges. Patients may have systemic manifestations. Imaging studies can be useful to identify edema with stranding of the subcutaneous fat around the mesh and to identify fluid collections (seroma, hematoma, abscess). (See 'Clinical features and diagnosis' above.)

●Wound cultures should be obtained to help guide antibiotic therapy. If there are no systemic signs of infection, cultures should be obtained before starting antibiotics. When available, culture findings guide changes in antibiotic therapy. The bacteria typically implicated in mesh infections are those with the capacity to form biofilm, such as coagulase-negative staphylococci, S. aureus, and enteric gram-negative bacilli. Anaerobes are also potential pathogens. Rarely, mesh infections can be caused by Candida or mycobacteria. (See 'Wound/fluid cultures' above.)

●The initial management of wound infection following abdominal wall hernia repair includes empiric antibiotic therapy and aggressive wound drainage and debridement (as needed). Specific wound management depends upon the location and nature of the hernia repair. (See 'Treatment' above.)

•Patients with systemic signs of infection should be taken for immediate surgical debridement to drain purulent fluid collections, remove infected and/or necrotic tissue, and remove the mesh, if present. Debrided material should be sent for aerobic and anaerobic culture and the results of susceptibility results used to tailor choice of antibiotic therapy. (See 'Superficial incisional surgical site infection' above.)

•Patients without systemic signs can initially be managed with antibiotics and drainage alone. Most superficial incisional SSIs can be successfully managed without the need to remove the mesh. Drainage of the wound may require opening the skin incision, but localized fluid collections may be amenable to percutaneous drainage. If signs of superficial incisional SSI do not improve with antibiotic therapy, a deep incisional SSI should be suspected. If the wound infection is not responsive to antibiotics and drainage, surgical debridement should be performed. Whether to remove part of or all of the mesh is a matter of clinical judgment. Well-incorporated mesh may remain in place; however, mesh that is not incorporated can be usually be easily removed. Antibiotics should be administered for at least two weeks following removal of the mesh. (See 'Deep incisional surgical site/mesh infection' above.)

•If the hernia recurs following mesh removal, every attempt should be made to eradicate the infection before repeat hernia repair is performed. If this is not possible, methods are available to repair inguinal hernia without the use of mesh. (See "Open surgical repair of inguinal and femoral hernia in adults", section on 'Nonmesh repairs'.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Lawrence Kim, MD, who contributed to earlier versions of this topic review.