Mastitis

Background
Cross-section scheme of the mammary gland: 1) Chest wall 2) Pectoralis muscles 3) Lobules 4) Nipple 5) Areola 6) Lactiferous duct 7) Adipose tissue 8) Skin
  • Inflammation of the breast tissue - can be infectious or non-infectious in etiology.[1]
    • Continuum of disease - Plugged ducts → engorgement → non-infectious inflammation → infectious inflammation → abscess
    • Infection occurs due to bacterial colonization secondary to areolar inflammation and glandular obstruction
  • Often occurs during the first few weeks to months postpartum, usually staph species with breast milk as culture medium
  • Post-menopausal usually due to E. coli, Group D strep, Staph, anaerobes[2][3]
    • Usually sub-areolar area due to chronic duct inflammation
    • 40% recurrence rates even after I&D
  • Neonatal mastitis management is controversial, but typically requires IV and/or PO antibiotics with good staph coverage

Clinical Features
Mastitis of right breast
Mastitis localized to inferior portion of left breast.

Differential Diagnosis

3rd Trimester/Postpartum Emergencies

Diagnostic Evaluation
  • Ultrasound useful to identify abscess
  • Routine labs not indicated unless[1]:
    • Treatment failure
    • Recurrent episodes
    • Hospital-acquired
    • Severe cases with systemic illness

Management
  • If lactation mastitis, continue to breastfeed or pump, no need to dispose of breastmilk
  • Warm compresses and massage, wearing supportive bra

Antibiotics
  • No need to routinely interrupt breastfeeding with puerperal mastitis.
  • For mild symptoms <24 hours, supportive care may be sufficient[1]
    • Effective milk removal (frequent breast feeding - use pumping to augment milk removal)
    • Analgesia (NSAIDs)

Treatment directed at S. aureus and Strep and E. coli

  • Uncomplicated mastitis → 10 days of antibiotics (regardless of MRSA suspicion)[4]
  • Dicloxacillin 500mg PO q6hrs, considered first line if breastfeeding given safety for infant OR
  • Cephalexin 500mg PO q6hrs OR
    • Add TMP/SMX 2DS tabs PO q12hrs if suspect MRSA
  • Clindamycin 450mg PO q8hrs (also provides MRSA coverage) OR
  • Amoxicillin/Clavulanate 875mg PO q12hrs OR
  • Azithromycin 500mg PO x1 on day 1, then 250mg PO daily for days 2-5

Abscess
  • Antibiotics as above
  • If fluid collection is greater than 2cm, evacuation is recommended, with culture and sensitivity to guide antibiotic therapy
    • If superficial <1cm from skin, I&D at bedside is recommended
    • If deep >1cm, consider percutaneous 18g needle aspiration. Percutaneous aspiration may also be appropriate for superficial abscess in a lactating patient to avoid milk duct fistula.
    • if palpable mass persists after 14-21 days, ultrasound and needle biopsy should be performed of solid components by radiology department

Disposition
  • Discharge, typically
  • If signs of sepsis or WBC >15K or with left shift, consider IV antibiotics and admission
  • Consider referral for outpatient Specialty Breast Services:
    • recurrent mastitis/abscess, or chronic granulomatous mastitis

References
  1. Amir LH. ABM Clinical Protocol #4: Mastitis, Revised March 2014. Breastfeeding Medicine. 2014;9(5):239-243. doi:10.1089/bfm.2014.9984.
  2. Eryilmaz R et al. Management of lactational breast abscesses. Breast. Oct 2005;14(5):375-9.
  3. Dixon JM. Outpatient treatment of non-lactational breast abscesses. Br J Surg. Jan 1992;79(1):56-7.
  4. Levine BL. 2011 EMRA Antibiotic Guide. EMRA. Pg 78.
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