The principles of incisional hernia repair in the setting of surgical field contamination involve the removal of the source of contamination and the reconstruction of the abdominal wall. These operations are challenging and often result in complications that lead to both surgeon and patient frustration [1
Colonic operations are classified as contaminated and infected (class 3-4) procedures according to Altemeier classification. For this reason the use of mesh in potentially contaminated procedures has been strongly discouraged [7
]. Morris et al. [8
] suggest abandonment of the use of mesh for repairs in which open bowel is encountered. A trend of increased pain and more severe wound infections after mesh repair were the basis for discontinuation of randomized control trial by Korenkov et al., [9
] highlighting the risk of using a foreign body in a hernia repair. Temudom et al. [10
] in a series of 50 complex prosthetic giant ventral hernia repairs reported that the two patients with simultaneous bowel surgery subsequently required mesh removal. Others [9
]recommend that intestinal resection be done first and hernia repair should be postponed for a second time.
The use of mesh is sometime necessitated by the size and the nature of defect. More than half of the patients in our study had either large or multi-loculated hernias. The defects were too large to be repaired primarily. McLanahan et al. [11
] reported no increased infectious risk with the prosthetic placement in a series of mostly clean-contaminated wounds having mesh incisional herniorrhapy. Vix et al. [4
], Birolini et al. [12
], Geisler et al. [13
] and more recently Machiaras et al. [7
] report 10.6%, 20%, 7% and 15.7% wound related morbidity respectively with the use of mesh in clean-contaminated and contaminated procedures. Campanelli et al. [14
] performed ten prosthetic hernia repairs in potentially contaminated areas and report that there were no major or minor complications after a 21 months follow-up period. These authors advocated the use of non-absorbable mesh in potentially contaminated and contaminated operations including colonic resections, with results as good as those observed in clean procedures.
The overall 28.3% infection rate in this study is significantly higher compared to the previous studies. Kelly et al. [3
] reported 21% infection rate in a series of emergency and elective incisional hernia repairs. Infection rates were 21% and 4% as reported by Alaedeen et al [1
] and Ahmed et al. [15
] in a similar patient casemix. The higher than usual infection rate in this study is attributable to the unique set of patients. We focused exclusively on a subset of incisional hernia repair cases which presented with an obstructed bowel and required emergency surgery, which carry higher risk of post-operative complications and have less favorable outcome [2
]. Davies et al [2
] found 10% infection rates in patients requiring emergency repair for all abdominal hernias. None of above quoted studies has focused on the subset of patients addressed in our study. Most of these studies include elective contaminated cases as a bulk of their population.
In view of the high infection rates, various techniques for mesh placement, including onlay, sublay (retromuscular or extrafascial), or underlay (intraperitoneal or subfascial), have been investigated. Rives-Stoppa technique has been advocated to have low infection rates, ranging between 2% and 17% [16
]. However, most of these studies did not focus exclusively on emergency repair of incarcerated hernias. In addition, this procedure is time consuming, as shown by longer mean length of operation time (131 minutes primary, 141 minutes mesh, 231 minutes Stoppa) in a study by Veillette et al [17
]. Patients with incarcerated incisional hernia with bowel obstruction are usually hemodynamically unstable. Therefore utility of time-consuming Stoppa technique in such patients is yet to be established.
The infection rate also depends on the need for concurrent bowel resection. It is 38% for patients needing concurrent bowel resection and 28% for those without bowel resection. The high wound infection in patients without bowel resection is postulated to be secondary to bacterial translocation thus an obstructed bowel is a significant risk factor for wound infection.
However, in view of the high infection rates, the option in operating room with a large defect and potentially contaminated field is to use absorbable mesh for temporary closure and do a definitive repair as a second planned operation.
In this study, the wound was left open in five patients to heal secondarily with granulation tissue. The decision to do so was made intra-operatively in light of grossly contaminated surgical field which made placement of prosthetic mesh a risky option. In addition absorbable (biological) mesh is not available in Pakistan. Post-operatively, the wounds took 4-5 months to heal depending upon size of the defect. These patients were advised to continue routine activities and once or twice daily self-wound care using a guaze once granulation had occurred. Patients were followed in the clinic on monthly basis till the wound healed completely. We did not have chronic draining sinuses in our patients.
Healthy pink granulation tissue covering the mesh.
In our experience, use of prolene mesh in contaminated fields is associated with high rates of wound infection, however mesh removal is rarely needed. All except one patient were treated with wound debridement or antibiotics. The evidence that prolene mesh is resistant to infection is also borne out by studies on Lichenstein hernia repair [18
]. The authors in view of the physical characteristics of prolene mesh, that is the mononfilament structure that allows the neutrophils and macrophages to eradicate bacteria, placed the mesh in an onlay position and allowed the wound to granulate and incorporate the mesh. The growth of granulation tissue through the intricese of the mesh is a unique phenomenon. This requires daily change of wound dressing and complete wound healing can take up to a year. The mesh eventually gets incorporated and epithelilized. In one patient mismatch in the wound contraction and mesh contraction resulted in partial auto explanation of the mesh as shown in the picture; this was excised.
Figure and Figure
Mesh partially incorporated with central part auto explanted due to wound contraction.
Final outcome of leaving the mesh exposed showing neo-epithelization in a patient after 5 years.