History and exam

Key diagnostic factors

common

fever

Mastitis may occur with or without pyrexia >38°C (>100.4°F).

Breast abscess may or may not be accompanied by fever.[1]

decreased milk outflow

Milk stasis may be associated with the development of mastitis.[1]

breast warmth

Tactile breast warmth is suggestive of mastitis and a possible underlying abscess.[1]

Lactational mastitis tends to involve more peripheral wedge-shaped areas.

breast tenderness

Breast tenderness is suggestive of mastitis and/or abscess.[1]

Lactational mastitis tends to involve more peripheral wedge-shaped areas.

breast firmness

Breast firmness can be suggestive of mastitis and a possible underlying abscess when accompanied by other signs of mastitis.[1]

Lactational mastitis tends to involve more peripheral wedge-shaped areas.

breast swelling

Breast swelling can be suggestive of mastitis and/or abscess when accompanied by other signs of mastitis.[1]

Lactational mastitis tends to involve more peripheral wedge-shaped areas.

Swelling may indicate skin oedema and/or underlying abscess formation.

breast erythema

Redness of the skin of the breast (erythema) can be suggestive of mastitis and a possible underlying abscess.[1][Figure caption and citation for the preceding image starts]: Non-lactating breast abscess due to peri-ductal mastitisFrom the collection of Mr R. Vashisht, West Middlesex University Hospital, London; used with permission [Citation ends].com.bmj.content.model.Caption@2d2ca6d6

Lactational mastitis tends to involve more peripheral wedge-shaped areas.[Figure caption and citation for the preceding image starts]: A breast abscess that developed during breastfeedingFrom the collection of Mr R. Vashisht, West Middlesex University Hospital, London; used with permission [Citation ends].com.bmj.content.model.Caption@5b3738d8

flu-like symptoms, malaise, and myalgia

Patients with mastitis and/or breast abscess may complain of systemic symptoms.[1]

breast pain

Usually sharp, shooting, or throbbing breast pain, especially with breastfeeding, may indicate mastitis.[1]

uncommon

breast mass

Breast mass may occur with a tender area of localised mastitis or breast abscess.

A late abscess may result in a fluctuant palpable mass.[1]

fistula

A fistula is usually associated with a draining sinus from an underlying abscess.[1]

Other diagnostic factors

uncommon

nipple discharge

May occur with or without mastitis.

Often associated with duct ectasia (dilated breast duct associated with inflammation).

Purulent discharge is usually indicative of infection.

nipple inversion/retraction

Infrequently seen with mastitis.

lymphadenopathy

Tender axillary lymph nodes may occur with ipsilateral breast infection.

extra-mammary skin lesions

Patients with mastitis and/or breast abscess may present with systemic signs including extra-mammary skin lesions.

Risk factors

strong

female sex

Breast infection more frequently involves the female breast.

Inflammation of the male breast may occur but is unusual.

poor breastfeeding technique

Poor breastfeeding positioning, or oral infection, tongue-tie, a skin infection, and nappy rash in the infant may be associated with the development of lactational mastitis.

lactation

Lactational mastitis is more common at 6-8 weeks of breastfeeding or at weaning.[5]​ Mastitis is uncommon during pregnancy itself.

milk stasis

Milk stasis is associated with infectious (lactational) and non-infectious mastitis.

Milk stasis is may result from inadequate drainage, blocked ducts, milk oversupply, external pressure on the breast (e.g., tight-fitting bra), infrequent feeding, or rapid weaning.[1]

nipple injury

Nipple cracks and fissures permit bacteria to gain entry into the breast.[2]

Injury may occur when an older teething baby bites a nipple or from use of a breast pump that generates excessive vacuum.

previous mastitis

Women who have had mastitis have an increased rate of recurrence with subsequent births.[2]

prolonged mastitis (breast abscess)

Prolonged mastitis may be associated with breast abscess formation.

women aged >30 years (breast abscess)

Women aged >30 years have a higher risk of breast abscess.[21]

prior breast abscess (breast abscess)

There is a high rate of recurrence with a remote history of prior breast abscesses.

shaving or plucking areola hair

Pulling hair from the areola may cause a Montgomery follicle abscess with potential for more widespread infection.

anatomical breast defect, mammoplasty, or scar

Altered duct structure may interfere with milk flow and predispose to mastitis.

other underlying breast condition

Particularly breast cancer.

nipple piercing

Breast infection may develop up to 52 weeks after piercing in 10% to 20% of cases.[19] The presence of nipple rings is also associated with an increased likelihood of needing repeat procedures for resolution of breast abscess.[22]

foreign body

Silicone and breast implants may cause mastitis with or without infection.[23]

Silicone mastitis may cause a hard, tender, erythematous breast mass.

skin infection

Dermatoses, such as psoriasis or eczema, may cause nipple fissures that result in recurrent mastitis.

Afflicted women are also more likely to harbour Staphylococcus aureus.

Staphylococcus aureus carrier

The vast majority of cases of infectious mastitis and breast abscess are caused by S aureus. Some studies have found that women who carry S aureus on the nipple, or have S aureus present in milk, are more likely to have lactational mastitis.[2]

immunosuppression

Patients with diabetes or HIV infection, and those on immunosuppression therapy, are at risk for developing breast infections.[16]

Diabetes mellitus is strongly associated with breast abscess in non-lactating women.[24]

weak

hospital admission

Epidemic (hospital-acquired) puerperal mastitis should be considered in any patient with signs of breast infection during or after a hospital admission.

breast trauma

Trauma to the breast may infrequently result in inflammation.

Domestic violence in such cases should always be considered.[1]

primiparity (breast abscess)

Found to be a risk factor for breast abscess in one population-based study.[21]

multiparity

Multiparity has been associated with increased risk of lactational mastitis.[2]

overabundant milk supply

For example, as may occur with lactation for twins or higher multiples.

May predispose to milk stasis.[1]

complications of delivery

May increase the risk of lactational mastitis.[1]

maternal stress

Maternal stress has been associated with lactational mastitis.[2]

tight clothing

Believed to promote milk stasis.[1] Associated with increased risk of lactational mastitis in some studies.[2]​​

antifungal nipple cream

Repeat application of antifungal cream for nipple thrush may cause nipple injury and possibly a change in normal flora.​[2][25]​​

fibrocystic breast disease

Fibrocystic breast disease may interfere with milk flow.

cigarette smoking

Smoking hinders the breast milk ejection reflex and raises the risk of engorgement and subsequent lactational mastitis.

Smoking is also associated with non-lactational mastitis in young women, as well as primary and recurrent breast abscess.[26][27]

vaginal manipulation (breast abscess)

Resulting transient bacteraemia is believed to be associated with anaerobic breast abscess formation.[28]

antiretroviral therapy

In HIV-infected breastfeeding women, mastitis or breast inflammation is a possible adverse effect of maternal prophylactic HIV antiretroviral therapy, and of infant nevirapine prophylaxis.[29]

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