Puerperal mastitis

Puerperal mastitis refers to mastitis occurring during pregnancy and lactation.

Epidemiology

It occurs most often during breast feeding and is rarely encountered during pregnancy.

Pathology

The source of infection is the nursing infants nose and throat; the organisms being Staphylococcus aureus and Streptococcus spp. Due to a breach in the nipple-areola complex, such as a cracked nipple, there is retrograde dissemination of these normal commensals. This is further favored by stasis of milk as stagnant milk is an excellent medium for bacterial growth.

Staphylococcus aureus infections tend to be more invasive and localized leading to earlier abscess formation; while Streptococcus infections tend to present as diffuse mastitis with focal abscess formation in advanced stages.

Subtypes

• endemic/sporadic: majority of the cases
• epidemic type: less common; can be life-threatening and is related to methicillin-resistant Staphylococcus aureus (MRSA)

Radiographic features

Mammography

• not usually done
• skin and trabecular thickening due to breast edema
• abscess may be seen as ill-defined mass 

Ultrasound

• primary modality of choice
• abscess: irregular, hypoechoic to anechoic mass with fluid and debris and posterior acoustic enhancement
• mastitis: ill-defined, hypoechoic region
• periductal inflammation
• guidance for abscess drainage

Treatment and prognosis

• antibiotic therapy 
• drainage of abscess

Differential diagnosis

Neoplasm should be suspected if the condition does not improve with antibiotic therapy.