Clinical Notes : Pharmacology

203. Mastitis and Breast Abscess

 

OVERVIEW

What is it ? (1) (2) (3) (4) (5) (6) (7)

  • Mastitis is a painful inflammatory condition of the breast. It usually occurs in lactating women ('lactational' or 'puerperal mastitis') but can also occur in non-lactating women ('non-lactational mastitis').

    • Mastitis can be classified as:

      • Non-infectious — breast inflammation due to a non-infectious and/or idiopathic cause.

      • Infectious — infection of breast tissue which usually occurs by retrograde spread through a lactiferous duct or a traumatized nipple. Very rarely, the infection occurs through the lymphatics or by haematogenous spread.

 

  • A breast abscess is a localized collection of pus within the breast.

    • A lactational abscess is usually located in the peripheral region of the breast, more commonly in the upper and outer quadrant.

    • A non-lactational abscess tends to be located in the central/subareolar or lower quadrants of the breast

 

What are the causes​ ?

  • In lactating women, milk stasis is usually the primary cause of mastitis (1) (3) (5) (8)

    • The accumulated milk causes an inflammatory response which may or may not progress to infection.

    • The most common organism associated with infectious mastitis in breastfeeding women is Staphylococcus aureus, including strains of Meticillin-resistant S. aureus (MRSA) if the infection was hospital-acquired.

  • In non-lactating women, mastitis is usually accompanied by infection, which can be categorized as either central/subareolar or peripheral (3) (9).

    • Central/subareolar infection is usually secondary to periductal mastitis (a condition where the subareolar ducts are damaged and become infected). Less commonly, it may be caused by duct ectasia, a harmless, age-related breast change (9)

    • Peripheral non-lactating infection (less common) has been associated with diabetes mellitus, rheumatoid arthritis, trauma, corticosteroid treatment, and granulomatous lobular mastitis (GLM), but often there is no underlying cause.

      • GLM is a rare inflammatory disease of the breast which is thought to be an autoimmune reaction to substances secreted from the mammary ducts (3). It can be idiopathic or occur in people with certain risk factors, although it is not exactly clear how it develops.

    • The most common organisms associated with infectious mastitis in non-lactating women are S. aureus, enterococci, and anaerobic bacteria (such as Bacteroides spp and anaerobic streptococci) (3) (9)​

 

  • A breast abscess is a severe complication of mastitis, although it may occur without apparent preceding mastitis (1) (3) (5) (8)

What are the predisposing factors ? 

A. Predisposing factors for mastitis in lactating women (1) (5) (8) (10) (11) (12)

  • Milk stasis is the primary cause of mastitis in lactating women. Predisposing factors include:

    • Poor infant attachment to the breast, for example due to:

      • Infant mouth abnormalities (for example cleft lip or palate) — this may also lead to nipple damage which can cause pain and provide an entry point for bacteria.

      • A short frenulum (tongue-tie) in the infant.

    • Reduced number or duration of feeds, for example due to:

      • Partial bottle feeding, changes in feeding regime (common when the infant first starts to sleep through the night), and rapid weaning from breast milk.

      • Painful breasts.

      • Use of a dummy or bottle — this may also result in poor infant attachment to the breast.

      • Having a preferred breast for feeding, leading to milk accumulation in the other breast.

      • Maternal stress and fatigue.

    • Pressure on the breast, for example from tight clothing or bra, a car seat belt, or prone sleeping position.

  • Other predisposing factors include:

    • Age — one retrospective study identified by the World Health Organization (WHO) showed that women aged 21–35 years are more likely to develop mastitis than those outside this age group. Another retrospective study identified women aged 30–34 years as having the highest incidence of mastitis, even when parity and full-time employment were controlled for.

    • Non-lactational predisposing factors, such as smoking, nipple damage, trauma to the breast, an underlying breast abnormality, and immunosuppression — see the section on Non-lactatiional mastitis for more information.

 

  • There is no evidence that breast size is related to the incidence of mastitis.

 

  • Recurrence of lactational mastitis is common. Predisposing factors include:

    • Staphylococcus aureus carriage — asymptomatic carriage of S. aureus on a person's skin or mucous membranes (colonization) is implicated in recurrent infections. For more information, see Scenario: Staphylococcal carriage in the Prodigy topic on Boils, carbuncles, and staphylococcal carriage.

    • Previous mastitis — this association is thought to be due to inadequate treatment of previous mastitis (which can lead to a recurrence of more severe mastitis or a breast abscess) and/or inadequate management of predisposing factors.

B. Predisposing factors for mastitis in non-lactating women

 

  • Smoking is the main predisposing factor for periductal mastitis. Nicotine and other toxins found in cigarette smoke accumulate in the breasts causing damage to the ducts (directly or by a localized hypoxic effect) (4) (5) (13)

 

  • Other predisposing factors for mastitis include:

    • Nipple damage, for example from nipple piercing or skin conditions such as eczema, infection, or Raynaud's disease — this can cause pain and provide an entry point for bacteria.

    • Trauma to the breast — may damage duct and gland tissue.

    • Underlying breast abnormality, such as ductal abnormality, cyst, or tumour — can cause persistent poor drainage of part of the breast, leading to breast infection.

    • Immunosuppression — women with diabetes mellitus or HIV infection, and those on immunosuppressive therapy, are at increased risk for developing breast infections.

    • Shaving or plucking areolar hair — pulling hair from the areola may result in the formation of a boil or an abscess, with potential for more widespread infection.

    • Foreign body — materials such as silicone and paraffin, which are used for both breast augmentation and reconstruction, may cause a foreign body-type reaction in the breast.

 

  • Predisposing factors for granulomatous lobular mastitis include bacterial infections (Corynebacterium spp), childbirth, oral contraceptive use, and conditions such as tuberculosis, sarcoidosis, and diabetes mellitus (14) (15) (16)

  • Recurrence of non-lactational mastitis is common. Predisposing factors include:

    • Staphylococcus aureus carriage — asymptomatic carriage of S. aureus on a person's skin or mucous membranes (colonization) is implicated in recurrent infections. For more information, see Scenario: Staphylococcal carriage in the Prodigy topic on Boils, carbuncles, and staphylococcal carriage.

    • Previous mastitis — this association is thought to be due to inadequate treatment of previous mastitis (which can lead to a recurrence of more severe mastitis or a breast abscess) and/or inadequate management of predisposing factors.

 

C. Predisposing factors for breast abscess

  • Predisposing factors for breast abscess include:

    • Previous mastitis — this association is thought to be due to (1) (12)

    • Delayed, inadequate, or inappropriate treatment of previous mastitis — can lead to complications, including a breast abscess.

    • Sudden cessation of breastfeeding in women with lactational mastitis — without effective milk removal, infectious mastitis is likely to progress to an abscess.

    • Immunosuppression — women with diabetes mellitus or HIV infection, and those on immunosuppressive therapy, are at risk for developing recurrent breast infections (5) (6)

    • Staphylococcus aureus carriage — asymptomatic carriage of S. aureus on a person's skin or mucous membranes (colonization) is implicated in recurrent infections. For more information, see Scenario: Staphylococcal carriage in the Prodigy topic on Boils, carbuncles, and staphylococcal carriage.

    • Poor socio-economic status — there is some evidence of a higher incidence of breast abscess (especially lactational) in low income women compared with higher income women (6)

    • Poor hygiene — better maternal and infant hygiene reduces the risk of abscess formation (4)

 

How common is it ?

  • Lactational mastitis

    • About 10–33% of lactating women develop mastitis (1) (3)

    • Most women who develop lactational mastitis do so within the first 6 weeks post-partum, although it can develop during weaning.

  • Non-lactational mastitis

    • Periductal mastitis occurs in 5–9% of non-lactating women. It can affect women of all ages but is more common in younger women (average age of 32 years) (5)

    • Granulomatous lobular mastitis is rare. Although it usually affects women of childbearing age, it can also occur in nulliparous women [Hovanessian (15).

  • Breast abscess

    • Breast abscesses develop in 3–11% of women with mastitis, with a reported incidence of 0.1–3% in lactating women (5)

What is the prognosis ?

  • When treated promptly and appropriately, recovery from mastitis or a breast abscess is usually prompt and complete. However, if treatment is delayed, inadequate, or inappropriate, the woman may develop serious complications.

 

  • Recurrence of mastitis or breast abscess is common:

    • The World Health Organization (WHO) found that more than half of women with lactational mastitis had experienced at least one previous episode (1)

    • Abscesses associated with periductal mastitis have a high recurrence rate because treatment (aspiration or incision) does not usually remove the underlying diseased duct, and most people continue to smoke — smoking is the main predisposing factor for this condition.

    • Granulomatous lobular mastitis has a recurrence rate of 50%, and there is a strong tendency for the condition to persist for months or years (4) (5)

What are the complications ?

  • Complications include:

    • Breast abscess — a study (combined results of a randomized controlled trial and a survey) of 171 women treated with antibiotics for mastitis found that 3% developed a breast abscess (8)

    • Mammary duct fistula — recurrent episodes of periductal mastitis and infection can result in mammary duct fistula (3)

    • Sepsis — breast infections may be associated with bacteraemia, especially in immunocompromised people.

    • Scarring — mastitis and breast abscesses are unlikely to cause significant breast scarring. However:

    • Surgical intervention other than needle aspiration may cause a post-operative scar.

    • Recurrent mastitis may lead to chronic inflammation and disfigurement of the breast.

    • Additional infections — mastitis may be the initiating factor for necrotizing fasciitis, especially in children. In addition, people with Staphylococcus aureus mastitis are at increased risk for subsequent skin infections at extra-mammary sites.

    • Death — mastitis and breast abscesses can occasionally be fatal if inadequately treated, especially in women who are immunocompromised (1)

 

  • Additional complications in lactating women include (1)

    • Emotional distress due to unplanned early cessation of breastfeeding.

    • Inability to breastfeed in the future — future lactation may be compromised in up to 10% of women who have had a breast abscess.

DIAGNOSIS of MASTITIS

When should I suspect mastitis ? (1) (3) (4) (13) (14) (15) (16) (17) (18) (19) (20) (21)

  • Suspect mastitis in a woman who presents with:

    • A painful breast.

    • Fever and/or general malaise.

    • A tender, red, swollen, and hard area of the breast, usually in a wedge-shaped distribution.

  • Be aware that the symptoms and signs of non-lactational mastitis may mimic breast cancer or a breast abscess:

    • Periductal mastitis may present with periareolar inflammation (with or without an associated mass), an established abscess, nipple retraction at the site of the diseased duct, central breast pain, and/or greenish discharge from the nipple.

    • Granulomatous lobular mastitis (GLM) may present with breast distortion, ulceration, or a large area (or areas) of infection with multiple simultaneous peripheral abscesses.

 

  • It is not possible to distinguish clinically between non-infectious and infectious mastitis. Suspect infectious mastitis if:

    • The woman has a nipple fissure that looks infected.

    • In a lactating woman:

    • Symptoms do not improve (or are worsening) after 12–24 hours despite effective milk removal.

    • Breast milk culture is positive. For information on when to arrange culture of the breast milk, see the section on Investigations.

When should I suspect a breast abscess ? (1) (3)

  • Suspect a breast abscess if the woman has:

    • A history of recent mastitis.

    • Fever and/or general malaise — these may have subsided if the woman has taken antibiotics for suspected infectious mastitis.

    • A painful, swollen lump in the breast, with redness, heat, and swelling of the overlying skin.

      • On examination, the lump may be fluctuant with skin discolouration.

When should I arrange a breast milk culture ? (1) (3) (10) (11) (12) (18)

  • Breast milk culture is not routinely required in primary care for women with mastitis.

    • However, in women with lactational mastitis, send a sample of breast milk for microscopy, culture, and antibiotic sensitivity, if:

      • Mastitis is severe or recurrent.

      • Hospital-acquired infection is likely.

      • There is severe deep 'burning' breast pain (indicative of ductal infection).

    • Advise the women on how to collect a sample of breast milk. She should:

      • Clean the nipple of the affected breast.

      • Express a small amount of milk by hand and discard it (to avoid skin contamination).

      • Express milk into a sterile container, avoiding touching the inside of the container with the nipple or hands.

What else might it be ?

  • Reassure

MANAGEMENT of LACTATIONAL MASTITIS

When should I arrange immediate admission or referral for a woman with lactational mastitis ?

  • In

How should I manage a woman with lactational mastitis in primary care ?

  • Consider

How should I manage treatment failure or recurrence in a woman with lactational mastitis ?

  • Reassure

What advice should I give to prevent recurrence of lactational mastitis?

  • In

MANAGEMENT of NON-LACTATIONAL MASTITIS

When should I arrange immediate admission or referral for a woman with non-lactational mastitis ?

  • Consider

How should I manage a woman with non-lactational mastitis in primary care ?

  • Reassure

How should I manage treatment failure or recurrence in a woman with non-lactational mastitis ?

  • In

What advice should I give to prevent recurrence of non-lactational mastitis ?

  • Consider

MANAGEMENT of BREAST ABSCESS

How should I manage a woman with a breast abscess ?

  • Reassure

 
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