Intraperitoneal Polypropylene Mesh in Clean, Potentially Septic, and Controlled Contamination Fields: An Experimental Rat Study

Background and Objectives: Intraperitoneal onlay mesh (IPOM) reduces ventral/incisional hernia recurrence but raises concern for adhesions and infection, particularly when the operative field is not strictly clean. We aimed to determine how contamination severity modulates the peritoneal response to intraperitoneal polypropylene mesh. Materials and Methods: In a prospective, randomized, blinded rat study, 60 male Wistar rats were allocated to three groups (n = 20/group) and evaluated at postoperative day (POD) 4 and POD 8 (n = 10/timepoint): A, clean mesh placement; B, small-bowel resection with end-to-end anastomosis without spillage (“potentially septic”); and C, mesh placement followed by intraperitoneal inoculation with Escherichia coli and Staphylococcus aureus (“controlled contamination”). The primary outcome was adhesion severity (Van der Ham scale, 0–3). Secondary outcomes included semi-quantitative histological scores (0–4) for neutrophil infiltration, fibroblast proliferation, neoangiogenesis, and collagen deposition. Prespecified non-parametric analyses were applied. Results: All animals completed follow-up; no pre-sacrifice deaths occurred. Adhesion severity showed no statistically significant differences between Groups A and B at either timepoint (mean POD4: 0.3 vs. 0.6; POD8: 0.4 vs. 0.8; p > 0.05). In contrast, Group C demonstrated markedly higher adhesion scores (mean POD4: 2.3; POD8: 2.4; both p < 0.001 vs. Groups A and B), with a substantially greater proportion of grade 2–3 adhesions. Histological parameters paralleled these findings: at both POD4 and POD8, Group C showed significantly higher neutrophil, fibroblast, neoangiogenesis, and collagen scores compared with Groups A and B (all p < 0.001). No statistically significant within-group temporal differences were observed between POD4 and POD8. Conclusions: In this experimental model, intraperitoneal polypropylene mesh demonstrated similar early biological response patterns in clean and controlled contamination settings, whereas established intra-abdominal sepsis was associated with a marked escalation of inflammation, fibroproliferation, and adhesion formation. These findings suggest that selective use of synthetic intraperitoneal mesh may be considered when contamination is controlled, while caution is warranted in frankly septic environments.