A 52-year-old man undergoes elective open cholecystectomy for symptomatic cholelithiasis. On postoperative day 5, the surgical wound shows erythema, warmth, and purulent discharge. Wound culture grows Staphylococcus aureus. The patient is afebrile with stable vitals. Histologically, the wound at this stage would show predominance of which cell type?

## Wound Healing Phase Analysis ### Timeline and Cellular Composition Postoperative day 5 falls within the **inflammatory phase** of wound healing, which typically spans days 1–5 (can extend to 7 days depending on contamination and infection severity). **Key Point:** The inflammatory phase is characterized by: - Neutrophil infiltration (peak at 24–48 hours) - Macrophage recruitment (peak at 48–72 hours) - Removal of debris, bacteria, and dead tissue - Release of growth factors (TGF-β, PDGF, FGF) ### Why Day 5 with Infection Shows Neutrophils and Macrophages In this case, the presence of **bacterial infection (S. aureus)** and **purulent discharge** indicates active inflammation. The wound is still in the inflammatory phase because: 1. **Neutrophils** are the primary responders to infection and bacterial load. 2. **Macrophages** are activated to phagocytose bacteria and damaged tissue. 3. The infection has **prolonged the inflammatory phase**, delaying transition to the proliferative phase. ### Phases of Wound Healing (Timeline) | Phase | Duration | Key Cells | Key Events | |-------|----------|-----------|------------| | **Hemostasis** | Minutes to hours | Platelets, RBCs | Clot formation, platelet plug | | **Inflammatory** | 1–7 days | Neutrophils, macrophages | Debridement, cytokine release | | **Proliferative** | 3–21 days | Fibroblasts, endothelial cells | Collagen deposition, angiogenesis | | **Remodeling** | 21 days–2 years | Fibroblasts, myofibroblasts | Collagen cross-linking, scar maturation | **High-Yield:** Infection **extends and exaggerates** the inflammatory phase. Neutrophils and macrophages persist as long as bacteria and necrotic tissue remain. ### Why Other Options Are Incorrect - **Fibroblasts and collagen deposition** → Characteristic of the **proliferative phase** (days 3–21), which is delayed or absent in active infection. - **Myofibroblasts and angiogenesis** → Peak during the **late proliferative and early remodeling phases** (after day 7–10). - **Epithelial cells and keratinocytes** → Involved in **epithelialization**, which occurs concurrently with inflammation but is not the predominant histologic finding in infected wounds. **Clinical Pearl:** Infected wounds show a **prolonged inflammatory response** with persistent neutrophilic infiltration and impaired transition to fibroblastic proliferation. This is why infection delays healing and increases scar formation.