A 38-year-old woman develops fever and cellulitis around her abdominal surgical wound 3 days after an open hysterectomy. Clinical examination reveals induration and erythema extending 5 cm beyond the wound margin, but no fluctuance or purulent drainage. Which investigation is most specific for detecting deep surgical site infection and guiding further management?

Explanation

## Investigation of Choice for Deep/Organ-Space SSI **Key Point:** Contrast-enhanced CT with IV contrast is the most specific imaging investigation for detecting deep surgical site infection, abscess formation, and determining the need for drainage or surgical intervention. ### Clinical Scenario Analysis The patient's presentation suggests **deep surgical site infection** or early organ-space infection: - Fever on postoperative day 3 - Cellulitis extending beyond wound margin (suggests deep involvement) - **Absence of purulent drainage** (rules out simple superficial infection) - Induration suggests fluid collection or deep inflammation ### Why CT is Superior Here ```mermaid flowchart TD A[Suspected Deep/Organ-Space SSI]:::outcome --> B{Clinical findings?}:::decision B -->|Purulent drainage only| C[Wound culture + empiric Abx]:::action B -->|Cellulitis + fever, no drainage| D[Imaging required]:::action D --> E{Imaging modality?}:::decision E -->|Superficial assessment| F[Ultrasound]:::action E -->|Detect abscess, fluid, deep involvement| G[Contrast-enhanced CT]:::action G --> H{Abscess present?}:::decision H -->|Yes| I[Percutaneous drainage + culture]:::action H -->|No| J[Empiric broad-spectrum Abx]:::action ``` **High-Yield:** CT sensitivity for abscess detection is >90%; ultrasound is operator-dependent and may miss deep collections. ### Advantages of CT in SSI | Feature | Ultrasound | CT | | --- | --- | --- | | **Abscess detection** | 70–80% | >90% | | **Depth assessment** | Limited | Excellent | | **Fluid characterization** | Possible | Excellent (Hounsfield units) | | **Organ involvement** | Poor | Excellent | | **Operator dependence** | High | Low | | **Radiation** | None | Yes | **Clinical Pearl:** IV contrast is essential to differentiate abscess (rim enhancement) from simple seroma (no enhancement). Non-contrast CT may miss subtle collections. ### Management After CT 1. **Abscess identified** → Percutaneous drainage (if >3 cm) + culture of drained fluid 2. **No abscess** → Broad-spectrum empiric antibiotics (cover gram-positive, gram-negative, anaerobes) 3. **Diffuse cellulitis** → Consider surgical exploration if patient deteriorates **Warning:** Do not delay empiric antibiotics while awaiting imaging if patient is systemically toxic. [cite:Sabiston Textbook of Surgery 21e Ch 12]