## Clinical Diagnosis: Acute Infectious Mastitis **Key Point:** The clinical presentation of unilateral erythema, induration, fever >39°C, systemic symptoms (malaise, chills), and localized breast pain on postpartum day 10 is diagnostic of **acute infectious mastitis**. ### Pathophysiology of Postpartum Mastitis Mastitis results from: 1. **Milk stasis** — inadequate emptying, poor latch, infrequent feeding 2. **Bacterial invasion** — most commonly *Staphylococcus aureus* (including MRSA), followed by *Streptococcus agalactiae* and *Escherichia coli* 3. **Inflammation and infection** — leading to tissue edema, erythema, and fever **High-Yield:** Mastitis occurs in 5–11% of breastfeeding women, typically after postpartum day 5. **Unilateral presentation with erythema and fever is pathognomonic.** ### Diagnostic Approach and Management Algorithm ```mermaid flowchart TD A[Unilateral Breast Pain + Erythema + Fever]:::outcome --> B{Fluctuance Present?}:::decision B -->|No fluctuance| C[Acute Mastitis]:::outcome B -->|Fluctuance present| D[Breast Abscess]:::outcome C --> E[Breast Ultrasound]:::action C --> F[Start Empiric Antibiotics]:::action C --> G[Continue Breastfeeding]:::action E --> H{Abscess Confirmed?}:::decision H -->|No| I[Antibiotics + BF + Supportive Care]:::action H -->|Yes| J[Ultrasound-Guided Aspiration or Drainage]:::action I --> K[Resolves in 48-72 hrs]:::outcome J --> L[Repeat Imaging if Needed]:::action ``` ### Management of Acute Mastitis (Without Abscess) **Step 1: Confirm Diagnosis** - **Breast ultrasound** — first-line imaging to rule out abscess (fluid collection) and assess extent of inflammation - Culture of expressed breast milk (optional but helpful for resistant organisms) **Step 2: Empiric Antibiotics** | Antibiotic | Dose | Duration | Notes | |-----------|------|----------|-------| | **Amoxicillin-clavulanate** | 625 mg TDS | 10–14 days | First-line; covers *S. aureus*, *Streptococcus*, *E. coli* | | **Cephalexin** | 500 mg QID | 10–14 days | Alternative if penicillin allergy | | **Cloxacillin** | 500 mg QID | 10–14 days | Better *S. aureus* coverage | | **Flucloxacillin** | 500 mg QID | 10–14 days | Preferred in UK; excellent *S. aureus* penetration | **Clinical Pearl:** If MRSA is suspected (healthcare-associated, recurrent, or non-response to beta-lactams), use **trimethoprim-sulfamethoxazole** or **clindamycin**. **Step 3: Continue Breastfeeding** - **Mandatory** — continued milk removal prevents abscess formation and improves antibiotic penetration - Milk is safe for infant (antibiotics are lactation-compatible) - Frequent feeding (8–12 times/day) recommended **Step 4: Supportive Measures** - Warm compresses before feeding - Proper latch assessment and correction - Analgesia (paracetamol, ibuprofen — safe in lactation) - Rest and hydration ### When to Suspect Abscess (Requires Drainage) **Red Flags:** - **Fluctuance** on examination (indicates fluid collection) - **Persistent fever** despite 48–72 hours of antibiotics - **Enlarging induration** or worsening erythema - **Imaging confirmation** — ultrasound shows hypoechoic collection >2 cm **Drainage Methods:** - Ultrasound-guided needle aspiration (preferred; minimally invasive) - Ultrasound-guided catheter placement - Surgical incision and drainage (reserved for failed aspiration or multiple locules) **Warning:** ~~Immediate surgical drainage~~ is not indicated in uncomplicated mastitis without confirmed abscess. ~~Cessation of breastfeeding~~ worsens outcome and increases abscess risk. ### Expected Clinical Course - **Symptom improvement:** 24–48 hours with appropriate antibiotics - **Complete resolution:** 10–14 days - **Recurrence rate:** 8% if inadequate treatment or persistent milk stasis [cite:Williams Obstetrics 25e Ch 37] [cite:RCOG Mastitis Guideline 2016] [cite:Park 26e Ch 8]
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