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Emergency and Acute Medicine – Mastitis
Basics description
Mastitis is an infection of the breast characterized by pain, swelling, erythema, and warmth, most commonly occurring in women who are breast-feeding. Systemic symptoms such as malaise and fever are frequent. Incidence may reach up to one-third of lactating women, with onset typically between 2–3 weeks and several months postpartum, most often before the infant is 3 months old. It is uncommon during the first postpartum week and is more frequent in advanced maternal age and patients with diabetes. Potential complications include recurrence, abscess formation, sepsis, necrotizing fasciitis, fistula, scarring, and breast hypoplasia. In rare cases, mastitis can occur in full-term infants younger than 2 months.
Etiology and risk factors
Staphylococcus aureus is the most common causative organism. Less frequent pathogens include coagulase-negative Staphylococcus, Streptococcus species, Escherichia coli, Haemophilus influenzae, and Candida albicans. Predisposing factors include cracked nipples, poor infant latch, local milk stasis, nipple piercing, poor maternal nutrition, prior mastitis, primiparity, tight bras, sore nipples, short infant frenulum, use of manual breast pumps, and maternal yeast infection.
Diagnosis signs and symptoms
Patients typically present with fever and chills, often exceeding 38.3°C, along with generalized malaise and tachycardia. Local findings include unilateral breast pain, induration, erythema, warmth, and swelling, sometimes in a wedge-shaped distribution. Decreased milk outflow and purulent nipple discharge may occur. Axillary lymphadenopathy can be present.
Essential workup and diagnostic testing
Diagnosis is primarily clinical. Careful breast examination is essential to assess for abscess formation, which may be subtle and is often periareolar. Breast milk cultures are generally unnecessary. Ultrasound should be obtained if abscess is suspected, while mammography is not indicated acutely. In neonates, evaluation for abscess and systemic infection is critical, and a sepsis workup may be required if the infant is febrile or ill appearing.
Differential diagnosis
Conditions to consider include breast engorgement, which is typically bilateral and occurs early postpartum with transient low-grade fever, inflammatory breast carcinoma, cysts or tumors, and breast abscess.
Treatment and emergency management
Breast-feeding should be continued whenever possible, as milk drainage is therapeutic and does not harm the infant. If the infant refuses milk from the affected breast, pumping and discarding milk is recommended. Supportive care includes breast massage, warm or cold compresses, hydration, and optimization of breast-feeding technique, often with lactation consultant support. Mild early cases may resolve without antibiotics. When antibiotics are required, oral therapy for 7–14 days is standard, with dicloxacillin or a first-generation cephalosporin as first-line options. Clindamycin, trimethoprim/sulfamethoxazole, or erythromycin may be used in penicillin-allergic patients or when MRSA is suspected, guided by local resistance patterns. Surgical consultation is indicated for suspected abscess.
Disposition and follow-up
Most patients can be managed as outpatients, with clinical improvement expected within 48 hours of therapy. Admission is indicated for patients requiring incision and drainage under anesthesia, those who are immunocompromised or septic, patients with diabetes and severe infection, and neonates with mastitis. Follow-up with a primary care physician is recommended, and lactation consultant involvement is often beneficial. Persistent or atypical cases should be evaluated to exclude inflammatory breast carcinoma.
Key points and cautions
Discontinuation of breast-feeding increases milk stasis and the risk of abscess formation. Many cases respond to supportive care alone, and unnecessary cessation of breast-feeding is a common and avoidable complication.
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