A 32-year-old multiparous woman, day 10 postpartum, presents with unilateral left breast pain, erythema over the upper outer quadrant, and a temperature of 38.8°C. She has been exclusively breastfeeding. On examination, there is a tender, indurated area in the left upper outer quadrant with overlying erythema, but no fluctuance. Milk from the affected breast appears normal. What is the most appropriate next step in management?

Explanation

## Clinical Diagnosis: Acute Mastitis **Key Point:** Acute mastitis presents with focal breast erythema, induration, and systemic signs (fever ≥38.5°C) and is typically caused by *Staphylococcus aureus* (including MRSA in some regions) or *Streptococcus agalactiae*. The diagnosis is clinical; imaging is not required for uncomplicated mastitis. **High-Yield:** Empiric oral antibiotics covering *S. aureus* (amoxicillin-clavulanate, cephalexin, or cloxacillin) are the first-line treatment. Breastfeeding must continue to prevent milk stasis and abscess formation. Most cases resolve within 48–72 hours of antibiotics. ### Diagnostic Criteria for Acute Mastitis | Feature | Present | Absent | |---------|---------|--------| | **Focal erythema** | ✓ | — | | **Induration/hardness** | ✓ | — | | **Fever ≥38.5°C** | ✓ | — | | **Systemic symptoms** | Malaise, myalgia | — | | **Fluctuance** | ✗ (rules out abscess) | — | | **Purulent discharge** | ✗ (rules out abscess) | — | ### Management Algorithm for Acute Mastitis ```mermaid flowchart TD A[Focal erythema + induration + fever ≥38.5°C]:::outcome --> B{Fluctuance or<br/>purulent discharge?}:::decision B -->|Yes| C[Suspect abscess]:::urgent B -->|No| D[Acute mastitis]:::outcome C --> E[Ultrasound ± FNA/aspiration]:::action E --> F[Antibiotics + possible I&D]:::action D --> G[Oral antibiotics]:::action G --> H[Continue breastfeeding]:::action H --> I[Warm compresses + analgesics]:::action I --> J[Review at 48 hrs]:::action J --> K{Clinical improvement?}:::decision K -->|Yes| L[Continue antibiotics 10–14 days]:::action K -->|No| M[Ultrasound to rule out abscess]:::action ``` ### First-Line Antibiotic Regimens | Antibiotic | Dose | Duration | Notes | |------------|------|----------|-------| | **Amoxicillin-clavulanate** | 500/125 mg TDS | 10–14 days | First-line; covers *S. aureus* and streptococci | | **Cephalexin** | 500 mg QID | 10–14 days | Alternative; good breast milk penetration | | **Cloxacillin** | 500 mg QID | 10–14 days | Alternative; preferred in some regions | | **Trimethoprim-sulfamethoxazole** | 1 DS tablet BD | 10–14 days | If penicillin allergy | **Clinical Pearl:** Absence of fluctuance or purulent discharge makes abscess unlikely. Imaging (ultrasound) is reserved for cases that do NOT improve within 48–72 hours of appropriate antibiotics or when abscess is clinically suspected. **Warning:** Do NOT delay antibiotics waiting for imaging in uncomplicated mastitis. Early antibiotic therapy prevents progression to abscess formation in >90% of cases. **Mnemonic:** **MASTITIS** — **M**ilk stasis, **A**ntibiotics (empiric), **S**taphylococcus/*Streptococcus*, **T**emperature ≥38.5°C, **I**nflammation (focal), **T**reatment (continue breastfeeding), **I**maging (only if no improvement), **S**ystemic signs. [cite:Williams Obstetrics 26e Ch 37; RCOG Green-top Guideline 20]