Reproductive · Infectious Mastitis
The facts most likely to be tested
Staphylococcus aureus is the most common causative pathogen in lactational mastitis.
Patients present with a unilateral, erythematous, tender, and indurated breast segment accompanied by fever and chills.
Continued breastfeeding or pumping is the first-line recommendation to prevent milk stasis and progression to abscess.
Dicloxacillin or cephalexin are the preferred first-line antibiotics for patients who do not improve with conservative management.
Clindamycin or trimethoprim-sulfamethoxazole are indicated for patients with a suspected methicillin-resistant Staphylococcus aureus (MRSA) infection or penicillin allergy.
A breast ultrasound is the diagnostic test of choice to differentiate mastitis from a breast abscess if a fluctuant mass is palpated or symptoms persist despite antibiotics.
Inflammatory breast cancer must be considered as a differential diagnosis if symptoms do not resolve after a course of appropriate antibiotic therapy.
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A 28-year-old primiparous woman who is 3 weeks postpartum presents to the clinic with a 2-day history of right breast pain. She reports that she has been exclusively breastfeeding. Physical examination reveals a fever of 101.5°F (38.6°C). The right breast shows a wedge-shaped area of erythema, warmth, and tenderness in the upper outer quadrant. There is no palpable fluctuance or mass. The patient's infant is feeding well, and the patient has no known drug allergies.
What is the most appropriate next step in management?
Continue breastfeeding and initiate dicloxacillin or cephalexin.
The patient presents with classic signs of lactational mastitis; the most important management steps are to ensure continued milk drainage and initiate empiric antibiotic therapy targeting S. aureus.
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Etiology / Epidemiology
Primarily affects lactating women due to milk stasis and nipple trauma, most commonly caused by Staphylococcus aureus.
Clinical Manifestations
Presents with unilateral localized breast pain, erythema, and warmth; flu-like symptoms are common.
Diagnosis
Clinical diagnosis; breast ultrasound is the gold standard if an abscess is suspected.
Treatment
Continue breastfeeding/pumping and initiate dicloxacillin or cephalexin; do not stop breastfeeding.
Prognosis
Most cases resolve with antibiotics; breast abscess is the primary complication requiring drainage.
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Epidemiology & Etiology
Occurs most frequently in the first 3 months postpartum. Primary risk factors include nipple trauma (cracked nipples) and infrequent feedings leading to milk stasis. Staphylococcus aureus is the most common pathogen, followed by Streptococcus species.
Pertinent Anatomy
The breast is composed of 15-20 lobes of glandular tissue. Infection typically involves the ductal system, where stagnant milk serves as a culture medium for bacterial growth.
Pathophysiology
Milk stasis leads to ductal obstruction, creating an environment for bacterial proliferation. The inflammatory response causes localized edema and systemic symptoms. If untreated, the infection progresses from cellulitis to a localized breast abscess.
Clinical Manifestations
Patients present with a tender, indurated, erythematous wedge-shaped area on the breast. Systemic symptoms include fever, chills, and malaise. Red flag: A persistent, fluctuant mass suggests an abscess requiring surgical evaluation.
Diagnosis
Diagnosis is primarily clinical based on physical exam. Breast ultrasound is the gold standard to differentiate simple mastitis from a breast abscess. Imaging is indicated if symptoms do not improve after 48-72 hours of antibiotics.
Treatment
First-line therapy is dicloxacillin or cephalexin for 10-14 days. Do not stop breastfeeding as it prevents further milk stasis. If MRSA is suspected, use clindamycin or trimethoprim-sulfamethoxazole. If an abscess is present, needle aspiration or incision and drainage is required.
Prognosis
Prognosis is excellent with prompt antibiotic therapy. Breast abscess is the most common complication, occurring in 5-11% of cases. Patients must be monitored for recurrence or failure to respond to initial therapy.
Differential Diagnosis
Breast abscess: presence of a fluctuant mass on ultrasound
Engorgement: typically bilateral and non-infectious
Galactocele: milk-filled cyst, usually non-tender
Inflammatory breast cancer: peau d'orange, no response to antibiotics
Ductal ectasia: chronic condition, usually non-lactating women