5.5 Mastitis – diagnosis
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![]() Key Points - Case Study EAnna is seven days postpartum. She is unsure whether she can continue to breastfeed her baby, Joshua, because of sore and cracked nipples. The cracks have increased in size since they first developed and it is excruciating to feed Joshua. What is the most likely cause of Anna's sore nipple?
What other conditions may contribute to nipple damage occurring in the first week postpartum?
After careful assessment, it appears that sub-optimal positioning and attachment issues are the cause of Anna's sore and cracked nipples. What is the most appropriate treatment to offer Anna at this stage?
Anna returns in a week. While there has been some improvement, she is still troubled by nipple pain. What causes should you now consider?
Anna's cracked nipples have some yellow exudate and appear inflamed. She is given a prescription for mupirocin; however, the next day she notices a firm, tender area in the upper inner aspect of her left breast that is gradually becoming more painful. She is beginning to feel unwell and has developed a fever. What is your diagnosis?
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Anna's cracked nipples have some yellow exudate and appear inflamed. She is given a prescription for mupirocin; however, the next day she notices a firm, tender area in the upper inner aspect of her left breast that is gradually becoming more painful. She is beginning to feel unwell and has developed a fever. What is your diagnosis?

© S.Cox IBCLC
The incidence of mastitis in breastfeeding women is approximately 20 percent, with most episodes occurring within the first three months (1,2,3,4). Mastitis is simply an inflammation in the breast and in the lactating breast manifests by a combination of the following symptoms:
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Local breast symptoms include:
- pain (can be quite severe and distressing);
- erythema;
- tenderness;
- lump;
- heat/warmth.
-
Systemic symptoms include:
- ever;
- rigors;
- myalgia; and
- malaise.
While usually unilateral, bilateral mastitis also occurs, especially in the first two weeks postpartum1. The severity of the symptoms and signs of mastitis varies considerably and it is not unusual to have a discrepancy between the severity of the local and systemic symptoms. More severe local symptoms at presentation tend to persist for longer1. Many women find mastitis quite debilitating, and some require hospitalisation. Some also report systemic symptoms before noticing any breast problems – mastitis should always be a differential diagnosis for a breastfeeding woman who presents with flu-like symptoms.
Mastitis is not always due to bacterial infection. Milk stasis can also lead to the release of cytokines into surrounding breast tissue causing an inflammatory response with local and systemic symptoms indistinguishable from those caused by a bacterial infection (5,6). While measuring the quantity of leukocytes and bacteria in the milk has been used by researchers to distinguish between infective and non-infective (inflammatory mastitis)7, it is of limited clinical use. Similarly, in the majority of circumstances, culturing breast milk provides only limited information for the clinician. First, it is difficult to obtain an adequate and uncontaminated specimen. Second, many specimens either do not grow anything, or grow bacteria regarded as normal skin flora. Additionally, it is often inappropriate to wait for microbiological results to commence treatment.
Staphylococcus aureus is the most common pathogenic bacteria associated with mastitis (6,7,8). Streptococci, especially B-haemolyitic streptococci (implicated in bilateral disease) and Escherichia coli, have also been known to cause mastitis9. MRSA has been cultured from breast milk and breast abscesses and should always be considered if mastitis is not responding to antibiotics as anticipated10. Additionally, bacteria regarded as normal skin flora have been grown from the milk of women with mastitis, occasionally in high concentrations. It is uncertain whether these bacteria are contaminants or have a pathological role in some instances6.
- Investigations
- For most women, investigations prior to commencing treatment are unwarranted. However, culture of a mid-stream specimen of milk from the affected breast is indicated if there is no response to antibiotic treatment within 48 hours, mastitis recurs despite apparently adequate treatment or there are other unusual features. If the mother is extremely ill, blood cultures and other investigations may also be necessary9.
- Differential diagnosis
-
- Engorgement.
- Blocked duct.
- Breast abscess – see below.
- Inflammatory carcinoma.
- Galactocoele.
What may predispose Anna to developing mastitis?
Click on the points below for more detail:
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Sore/cracked nipples
- Women with sore nipples only or with nipple cracks are more likely to develop mastitis, perhaps due to the retrograde spread of bacteria from the damaged nipple epithelium into the breast tissue. Nipple soreness with feeding, even when nipples look "normal", usually indicates some nipple trauma. Additionally, as discussed previously, nipple cracks may become colonised, with Staphylococcus aureus providing a ready source of infection. Anna's cracked nipple is an important predisposing factor for her developing mastitis (2,3,11,12,13).
-
Milk stasis (poor breast drainage)
- Inadequate breast drainage
- Suboptimal positioning and attachment of the infant at the breast, hurried or timed feeds, over-supply of milk, changes in feeding routines (i.e. infant sleeping through the night) or the replacement of breastfeeds with complementary feeds may all result in sections of one or both breasts not being adequately drained. While breasts are not fully emptied at every feed, each breast should be drained once per day. In Anna's case, her sore nipples suggest positioning and attachment difficulties. In addition, as breastfeeding with a cracked nipple is very painful, she may be hesitant attaching the infant to the breast and reluctant to allow the infant to stay attached for long enough to fully drain the breast (11,14).
- Engorgement
- Although engorgement usually occurs in the first week postpartum, women may develop engorged breasts if there is a long interval between feeds (11,15).
- Blocked ducts
- A description of the signs and symptoms of blocked ducts is in Table E.1. When milk is not removed from a section of the breast, for whatever reason, the risk of non-infective and then infective mastitis increases (12,14).
- Mechanical obstruction
- Mechanical obstruction of breast drainage. Pressure on the breast from clothing, seatbelts, breast pumps, nipple shields and nipple airers have been implicated in milk stasis and mastitis (11,13).
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Sources of staph infection
- Nasal carriage of Staphylococcus aureus in infants increases the risk of mastitis in their mothers11. It is also suggested that other sources of Staph infections such as contaminated nipple creams or other family members may also be implicated.
- Past history of mastitis
- Maternal factors (illness, depressed immune system)
Notes
- # Fetherston C (1997) Characteristics of lactation mastitis in a Western Australian cohort
- # Amir LH et al. (2007) A descriptive study of mastitis in Australian breastfeeding women: incidence and determinants
- # Vogel A et al. (1999) Mastitis in the first year postpartum
- # Kinlay JR et al. (1998) Incidence of mastitis in breastfeeding women during the six months after delivery: a prospective cohort study
- # Fetherston C (2001) Mastitis in lactating women: physiology or pathology?
- # Osterman KL et al. (2000) Lactation mastitis: bacterial cultivation of breast milk, symptoms, treatment, and outcome
- # Thomsen AC et al. (1984) Course and treatment of milk stasis, noninfectious inflammation of the breast, and infectious mastitis in nursing women
- # Amir LH et al. (1999) An audit of mastitis in the emergency department
- # World Health Organization WHO (2000) Mastitis: Causes and management
- # Reddy P et al. (2007) Postpartum mastitis and community-acquired methicillin-resistant Staphylococcus aureus
- # Amir LH et al. (2006) A case-control study of mastitis: nasal carriage of Staphylococcus aureus
- # Kinlay JR et al. (2001) Risk factors for mastitis in breastfeeding women: results of a prospective cohort study
- # Foxman B et al. (2002) Lactation mastitis: occurrence and medical management among 946 breastfeeding women in the United States
- # Fetherston C (1998) Risk factors for lactation mastitis
- # Wambach KA (2003) Lactation mastitis: a descriptive study of the experience