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Mastitis
Anne Claire Adams, MD
Montiel T. Rosenthal, MD
image BASICS
DESCRIPTION
  • Mastitis is an inflammation of the breast parenchyma and possibly associated tissues (areola, nipple, subcutaneous [SC] fat).
  • Usually associated with bacterial infection (and milk stasis in the postpartum mother)
  • Usually an acute condition but can become chronic cystic mastitis
EPIDEMIOLOGY
  • Predominantly affects females
  • Mostly in the puerperium; epidemic form rare in the age of reduced hospital stays for mothers and newborns
  • Neonatal form
  • Posttraumatic: ornamental nipple piercing increases risk of transmission of bacteria to deeper breast structures: Staphylococcus aureus is the predominant organism.
Incidence
  • 3-20% of breastfeeding mothers develop nonepidemic mastitis.
  • Greatest incidence among breastfeeding mothers 2 to 6 weeks postpartum
  • Neonatal form occurs at 1 to 5 weeks of age, with equal gender risk and unilateral presentation.
  • Pediatric form
  • Around or after puberty
  • 82% of cases in girls
ETIOLOGY AND PATHOPHYSIOLOGY
  • Microabscesses along milk ducts and surrounding tissues
  • Inflammatory cell infiltration of breast parenchyma and surrounding tissues
  • Nonpuerperal (infectious)
    • S. aureus, Bacteroides sp., Peptostreptococcus, Staphylococcus (coagulase neg.), Enterococcus faecalis
    • Histoplasma capsulatum
    • Salmonella enterica
    • Rare case of Actinomyces europaeus
  • Puerperal (infectious)
    • Staphylococcus aureus, Streptococcus pyogenes (group A or B), Corynebacterium sp., Bacteroides sp., Staphylococcus (coagulase neg.), Escherichia coli, Salmonella sp.
    • Methicillin-resistant S. aureus (MRSA)
  • Rare secondary site for tuberculosis in endemic areas (1% of mastitis cases in these areas): single breast nodule with mastalgia
  • Corynebacterium sp. associated with greater risk for development of chronic cystic mastitis
  • Granulomatous mastitis
    • Idiopathic
      • Predilection for Asian and Hispanic women
      • Association with &agr;-1-antitrypsin deficiency, hyperprolactinemia with galactorrhea, oral contraceptive use, Corynebacterium sp. infection, and breast trauma
      • Most women have a history of lactation in previous 5 years.
    • Lupus; autoimmune
  • Puerperal
    • Retrograde migration of surface bacteria up milk ducts
    • Bacterial migration from nipple fissures to breast lymphatics
    • Secondary monilial infection in the face of recurrent mastitis or diabetes
    • Seeding from mother to neonate in cyclical fashion
  • Nonpuerperal
    • Ductal ectasia
    • Breast carcinoma
    • Inflammatory cysts
    • Chronic recurring SC or subareolar infections
    • Parasitic infections: Echinococcus; filariasis; Guinea worm in endemic areas
    • Herpes simplex
    • Cat-scratch disease
  • Lupus
RISK FACTORS
  • Breastfeeding
  • Milk stasis
    • Inadequate emptying of breast
      • Scarring of breast due to prior mastitis
      • Scarring due to previous breast surgery (breast reduction, biopsy, or partial mastectomy)
    • Breast engorgement: interruption of breastfeeding
  • Nipple trauma increases risk of transmission of bacteria to deeper breast structures: S. aureus predominant organism
  • Neonatal colonization with epidemic Staphylococcus
  • Neonatal
    • Bottle-fed babies
    • Manual expression of “witch's milk”
    • Can predispose to lethal necrotizing fasciitis
  • Maternal diabetes
  • Maternal HIV
  • Maternal vitamin A deficiency (in animal models)
GENERAL PREVENTION
Regular emptying of both breasts and nipple care to prevent fissures when breastfeeding. Also good hygiene including hand washing and washing breast pumps after each use (1)[A].
COMMONLY ASSOCIATED CONDITIONS
Breast abscess
image DIAGNOSIS
  • Fever >38.5°C and malaise
  • Nausea ± vomiting
  • Localized breast tenderness, heat, swelling, and redness
  • Possible breast mass
PHYSICAL EXAM
  • Breast tenderness
  • Localized breast induration, redness, and warmth
  • Peau d'orange appearance to overlying skin
DIFFERENTIAL DIAGNOSIS
  • Abscess (bacterial, idiopathic granulomatous mastitis, fungal, tuberculosis)
  • Tumor
    • Idiopathic granulomatous mastitis
    • Inflammatory breast cancer
    • Wegener granulomatosis
    • Sarcoidosis
    • Foreign body granuloma
    • Vasospasm (may be presentation for Reynaud) (2)[B]
  • Ductal cyst (ductal ectasia)
  • Consider monilial infection in lactating mother, especially if mastitis is recurrent.
DIAGNOSTIC TESTS & INTERPRETATION
Initial Tests (lab, imaging)
Mastitis is typically a clinical diagnosis. Labs rarely needed. In those ill enough to need hospitalization, consider the following:
  • CBC
  • Blood culture
  • In epidemic puerperal mastitis
    • Milk leukocyte count
    • Milk culture
    • Neonatal nasal culture
  • No imaging required for postpartum mastitis in a breastfeeding mother that responds to antibiotic therapy.
  • Mammography for women with nonpuerperal mastitis
  • Breast ultrasound to rule out abscess formation in women
    • Special consideration for this in women with breast implants who have mastitis
Follow-Up Tests & Special Considerations
Lactating mothers produce salty milk from affected side (higher Na and Cl concentrations) as compared with unaffected side. Consider breast milk culture if suspect MRSA. Also consider testing for tuberculosis as may be initial presentation.
Diagnostic Procedures/Other
Options if further progression to abscess formation
  • Needle aspiration
  • Incision and drainage
  • Excisional biopsy
  • US-guided core needle biopsy is diagnostic method of choice for idiopathic granulomatous mastitis
image TREATMENT
A recent Cochrane review found that insufficient evidence exists to confirm or refute the effectiveness of antibiotic therapy for the treatment of lactational mastitis (3)[A]. If present <24 hours and symptoms are mild, conservative management with milk removal and supportive measures is recommended.
P.639

MEDICATION
  • Prioritized on the basis of likelihood of MRSA as etiologic factor and clinical severity of condition.
  • Treat for 10 to 14 days.
  • For idiopathic granulomatous mastitis and localized infection, usually resolves with antibiotics and drainage
First Line
  • Outpatient
    • Effective milk removal is the most important management step (4)[A].
    • Dicloxacillin 500 mg QID
    • Cephalexin 500 mg QID
    • Trimethoprim/sulfamethoxazole (TMP/SMX); DS BID (if mastitis not improving within 48 hours after starting first-line treatment consider MRSA)
    • Lactobacillus fermentum or Lactobacillus salivarius 9 log 10 CFU/day
  • Inpatient
    • Nafcillin 2 g q4h
    • Oxacillin 2 g q4h
    • Vancomycin 1 g q12h (MRSA possible)
  • Breastfeeding beyond 1 month
    • Penicillin, ampicillin, or erythromycin
If idiopathic granulomatous mastitis, consider corticosteroids ± methotrexate (5)[B]
Pediatric Considerations
TMP/SMX given to breastfeeding mothers with mastitis can potentiate jaundice for neonates.
Second Line
  • If mastitis is odoriferous and localized under areola, add metronidazole 500 mg TID IV or PO.
  • If yeast is suspected in recurrent mastitis, add topical and oral nystatin.
ISSUES FOR REFERRAL
  • Abscess formation
  • Need for breast biopsy
ADDITIONAL THERAPIES
  • Warm packs to improve blood flow and milk let down and/or ice packs to reduce inflammation to affected breast for comfort
  • The use of a breast pump may aid in breast emptying, especially if the infant is unable to assist in doing this.
  • Wear supporting bra that is not too tight.
SURGERY/OTHER PROCEDURES
In cases of biopsy-proven idiopathic granulomatous mastitis, surgical removal can result in a 5-50% chance of recurrence, fistula formation, and poor wound healing.
INPATIENT CONSIDERATIONS
If a new mother is admitted to the hospital for treatment of her mastitis, rooming-in of the infant with the mother is mandatory so that breastfeeding can continue (4)[C]. In some hospitals, rooming-in may require hospital admission of the infant.
Admission Criteria/Initial Stabilization
  • Failure of outpatient/oral therapy
    • Patient unable to tolerate oral therapy
    • Patient noncompliant with oral therapy
    • Severe illness without adequate supportive care at home
  • Neonatal mastitis
  • Antibiotics
  • Frequent emptying of breasts, if breastfeeding
  • Analgesics for pain
    • Ibuprofen
    • Acetaminophen
Nursing
  • Breastfeeding/pumping of breasts encouraged
  • Start infant with feedings on affected side.
  • Abscess drainage is not a contraindication for breastfeeding.
  • Massage in direction from blocked area toward nipple.
  • Positioning infant at breast with chin or nose pointing to blockage will help drain affected area.
Discharge Criteria
  • Afebrile
  • Tolerating oral antibiotics well
image ONGOING CARE
FOLLOW-UP RECOMMENDATIONS
Rest for lactating mothers, up to bathroom
DIET
  • Encourage oral fluids.
  • Multivitamin, including vitamin A
PATIENT EDUCATION
  • Encourage oral fluids.
  • Rest is essential
  • Regular emptying of both breasts with breastfeeding
  • Nipple care to prevent fissures
PROGNOSIS
  • Puerperal
    • Good with prompt (within 24 hours of symptom onset) antibiotic treatment and breast emptying; 96% success rate
    • 11% risk of abscess if left untreated with antibiotics
    • Antibodies develop in breast glands within first few days of infection, which may provide protection against infection or reinfection.
  • Rare risk of abscess formation beyond 6 weeks postpartum if no recurrent mastitis
REFERENCES
1. Crepinsek MA, Crowe L, Michener K, et al. Interventions for preventing mastitis after childbirth. Cochrane Database Syst Rev. 2012;(10):CD007239.
2. Buck ML, Amir LH, Cullinane M, et al. Nipple pain, damage, and vasospasm in the first 8 weeks postpartum. Breastfeed Med. 2014;9(2):56-62.
3. Jahanfar S, Ng CJ, Teng CL. Antibiotics for mastitis in breastfeeding women. Cochrane Database Syst Rev. 2013;(2):CD005458.
4. Amir LH. ABM clinical protocol #4: mastitis, revised March 2014. Breastfeed Med. 2014;9(5):239-243.
5. Sheybani F, Sarvghad MR, Naderi HR, et al. Treatment for and clinical characteristics of granulomatous mastitis. Obstet Gynecol. 2015;125(4):801-807.
Additional Reading
&NA;
Spencer JP. Management of mastitis in breastfeeding women. Am Fam Physician. 2008;78(6):727-731.
See Also
&NA;
Algorithms: Breast Discharge; Breast Pain
Codes
&NA;
ICD10
  • N61 Inflammatory disorders of breast
  • O91.22 Nonpurulent mastitis associated with the puerperium
  • O91.23 Nonpurulent mastitis associated with lactation
Clinical Pearls
&NA;
  • Complete emptying of the breasts on a regular schedule, avoiding constrictive clothing or bras that might obstruct breast ducts, meticulous attention to nipple care, “adequate rest,” and a liberal intake of oral fluids for the mother can all reduce the risk of a breastfeeding mother's developing mastitis.
  • First-line treatment for puerperal mastitis is dicloxacillin 500 mg PO QID for 10 to 14 days. Most mastitis can be treated with oral therapy.
  • Among breastfeeding mothers, if the symptoms of mastitis fail to resolve within several days of appropriate management, including antibiotics, further investigations may be required to confirm resistant bacteria, abscess formation, an underlying mass, or inflammatory or ductal carcinoma.
  • More than two recurrences of mastitis in the same location or with associated axillary lymphadenopathy warrant evaluation with ultrasound or mammography to rule out an underlying mass.