Mastitis and Breast Abscess

Introduction and classification

Breast infection divides into two clinically distinct groups that share almost nothing except their appearance. Lactational (puerperal) infection occurs in breastfeeding women, begins with milk stasis and is overwhelmingly staphylococcal. Non-lactational infection occurs outside pregnancy, is closely tied to smoking and duct disease, is more often mixed and anaerobic, and has a strong tendency to recur.

Mastitis affects an estimated 10 to 20% of breastfeeding women, most often in the first six weeks after delivery, and it is a leading reason for women stopping breastfeeding earlier than they intended. Around 3 to 11% of episodes progress to an abscess, and that progression is largely preventable.

Lactational mastitis

Pathophysiology

The sequence begins mechanically rather than infectively, and understanding this is what makes the management make sense.

1. Milk stasis in a segment of the breast, from a poor latch, a missed or shortened feed, pressure from a tight bra or a seatbelt, or oversupply
2. Rising intraductal pressure forces milk into the surrounding interstitium, where its proteins and fat provoke an inflammatory response - at this stage there is no infection, and this is why an early presentation may settle with drainage alone
3. Bacterial overgrowth in the stagnant milk, with organisms entering through a cracked or fissured nipple. Staphylococcus aureus is by far the commonest.
4. Infective mastitis, with cellulitis of the affected segment and systemic upset
5. Abscess formation, if drainage remains inadequate or treatment is delayed

Risk factors

• Poor latch or attachment, which is the underlying problem in a large proportion of cases and the reason a feeding assessment is part of treatment
• Nipple trauma, cracks and fissures, providing a portal of entry
• Missed, delayed or shortened feeds, and abrupt weaning
• Oversupply and engorgement
• External pressure - a tight or underwired bra, a sling, a seatbelt, or sleeping on the front
• Maternal fatigue, stress and illness
• Previous mastitis, which recurs in a significant minority

Clinical features

• A painful, red, hot, swollen area of the breast, characteristically wedge-shaped, corresponding to a segment rather than to the whole breast
• Flu-like systemic symptoms - fever, rigors, myalgia and malaise, which can be strikingly severe and out of proportion to the local signs
• Tachycardia and general malaise
• Nipple fissure or cracking, which should be looked for specifically
• A fluctuant, tender mass suggests an abscess has formed

Management

1. Effective milk removal - continued frequent feeding, expressing after feeds, varying feeding positions, and gentle massage towards the nipple
2. Feeding support and latch assessment, which is the single most important intervention for preventing recurrence
3. Analgesia - paracetamol and ibuprofen, both compatible with breastfeeding, and warm or cold compresses
4. Antibiotics if the woman is systemically unwell, has a nipple fissure, has symptoms that are not improving after 12 to 24 hours of effective milk removal, or has bacterial culture confirming infection. First line is flucloxacillin 500 mg four times daily for 10 to 14 days; erythromycin or clarithromycin if penicillin allergic.¹
5. Send a milk sample for culture if the infection is severe, recurrent, hospital-acquired or unresponsive to first-line treatment
6. Review within 48 hours, and re-examine anyone not improving
7. Arrange an ultrasound if there is a fluctuant or persistent lump, or no improvement despite adequate antibiotics

Breast abscess

Suspect an abscess when there is a fluctuant, tender, well-localised mass, when symptoms fail to settle within 48 hours of appropriate antibiotics, or when the systemic upset is disproportionate. Fluctuance is often difficult to elicit in an engorged lactating breast, so a low threshold for ultrasound is appropriate.

1. Ultrasound confirms the diagnosis, defines the size and number of collections, guides aspiration and distinguishes an abscess from cellulitis or a galactocele
2. Ultrasound-guided needle aspiration under local anaesthetic is first-line treatment, repeated every few days until the cavity resolves. It has largely replaced open drainage, produces a better cosmetic result, permits continued breastfeeding, and avoids a general anaesthetic in a woman with a young baby.²
3. Send the pus for microscopy, culture and sensitivity, and adjust antibiotics accordingly
4. Continue oral antibiotics alongside drainage
5. Incision and drainage is reserved for a large abscess, for overlying skin necrosis or a pointing abscess, and where repeated aspiration has failed. Place the incision to allow later cosmetic revision, and avoid a periareolar incision in a lactating woman if possible, since it risks damaging ducts.
6. Continue breastfeeding from both breasts wherever the mother is able. If the incision is close to the nipple and feeding is too painful, express from that side and continue feeding from the other.
7. Follow up to resolution, and consider imaging or biopsy of any residual mass

Non-lactational infection

Periductal mastitis

This is inflammation of the subareolar ducts, occurring typically in women in their thirties and forties and strongly associated with smoking - probably through direct toxic damage to the duct epithelium and local hypoxia. Around 90% of affected women are smokers.

• Periareolar pain, erythema and a tender mass, sometimes with a subareolar abscess
• Nipple discharge, often thick and creamy, and nipple retraction from fibrosis
• Mammary duct fistula - a chronic communication between a subareolar duct and the periareolar skin, discharging intermittently. This is the characteristic complication and often follows repeated abscess drainage.
• Treatment is with co-amoxiclav, or a macrolide with metronidazole in penicillin allergy, to cover the anaerobes involved, together with aspiration or drainage of any abscess
• Smoking cessation is the definitive intervention. Recurrence is very high in continuing smokers, and this should be stated plainly.
• Surgery - total duct excision (Hadfield procedure) or fistulectomy - is used for recurrent disease or an established fistula, and is best deferred until the acute inflammation has settled

Other non-lactational conditions

• Duct ectasia - dilated, shortened subareolar ducts with thick green, creamy or cheesy discharge from multiple ducts and slit-like nipple retraction. Benign and usually managed with reassurance; it may become infected as periductal mastitis.
• Idiopathic granulomatous mastitis - a rare chronic condition producing a firm mass, sinuses and abscesses that mimics carcinoma and tuberculosis. Diagnosis requires core biopsy and exclusion of infection, and treatment may involve corticosteroids or immunosuppression under specialist care.
• Tuberculous mastitis, which should be considered in women from high-prevalence regions with a chronic breast mass and sinuses
• Infection of a haematoma, a sebaceous cyst or a breast implant, and hidradenitis suppurativa affecting the inframammary fold

Differential diagnosis

A painful, red or swollen breast has a short list of explanations, and separating them mostly turns on whether the woman is lactating, whether the change is segmental, and whether there is systemic upset.

A useful practical sequence at the bedside is: is she lactating; is the redness segmental or diffuse; is there a fluctuant lump; and has she already had a course of antibiotics? The answers to those four questions separate almost every entry in the table above and determine whether the next step is a feeding assessment, an ultrasound, or a two-week wait referral.

Complications

• Breast abscess, in 3 to 11% of episodes of lactational mastitis
• Premature cessation of breastfeeding, which is the commonest adverse outcome and has consequences for both mother and infant
• Recurrent infection, particularly where the latch has not been corrected or where the woman continues to smoke
• Mammary duct fistula after periductal mastitis, which is difficult to treat and often needs surgery
• Scarring, distortion and nipple retraction, with cosmetic and psychological consequences
• Sepsis, which is uncommon but can be severe, particularly with group A streptococcal infection in the puerperium
• Delayed diagnosis of inflammatory breast cancer
• Maternal exhaustion, pain and low mood, which compound difficulties with feeding and should be asked about directly

Red flags

Prognosis

Lactational mastitis treated promptly, with effective milk removal and antibiotics where indicated, resolves within days and has no long-term consequence for the breast. Abscesses treated by repeated ultrasound-guided aspiration resolve in the great majority without an operation and with a good cosmetic result.

The outcome that is most often lost sight of is breastfeeding itself. A significant proportion of women stop feeding after an episode of mastitis, sometimes because they were advised to and sometimes because the pain and exhaustion were not adequately supported. Since milk stasis is the cause, continued feeding is both the treatment and the way to protect the feeding relationship, and the practical support around that matters as much as the prescription.

Non-lactational periductal mastitis has a considerably less satisfactory course. Recurrence rates in women who continue to smoke are high, mammary duct fistula is difficult to eradicate, and repeated drainage produces cumulative scarring. Smoking cessation is the intervention that changes the natural history, and it deserves to be presented to the patient as treatment rather than as general health advice.