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Acute Mastitis
Introduction
Mastitis is inflammation of the breast and can be categorized into lactational and non-lactational mastitis. Lactational mastitis is the most common form of mastitis. Non-lactational mastitis includes periductal mastitis and idiopathic granulomatous mastitis (IGM).
Lactational mastitis, or puerperal mastitis, is typically due to prolonged engorgement of milk ducts, with infection from bacterial entry through breaks in the skin. Patients can develop a focal area of erythema, pain, and swelling and can have associated systemic symptoms, most notably fever. This occurs most often in the first 6 weeks of breastfeeding but can occur at any time during lactation, with most cases decreasing after 3 months.[1]
Periductal mastitis is a benign inflammatory condition affecting the subareolar ducts and occurs most commonly in reproductive-aged women. Alternatively, IGM is a rare benign inflammatory condition that can clinically mimic breast cancer and occurs primarily in parous women ordinarily within 5 years of giving birth.[1]
Etiology
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Etiology
Lactational mastitis is most commonly caused by bacteria that colonize the skin, with Staphylococcus aureus being the most common. Methicillin-resistant S aureus (MRSA) has become an increasingly frequent cause of mastitis, and risk factors for MRSA should be considered. Other causative organisms include Streptococcus pyogenes, Escherichia coli, Bacteroides species, and coagulase-negative staphylococci. Risk factors for lactational mastitis include a prior history of mastitis, nipple cracks and fissures, inadequate milk drainage, maternal stress and lack of sleep, tight-fitting bras, and the use of antifungal nipple creams.[2][3]
The cause of periductal mastitis is not clear. Smoking may be associated with the development of the condition through direct damage to the ducts and subsequent inflammation. Bacteria are isolated in cultures in 62% to 85% of patients with periductal mastitis, and the most common causative organisms include S aureus, Pseudomonas aeruginosa, and Enterococcus, Bacteroides, and Proteus species.[4] Obesity and diabetes have also been proposed as possible risk factors.[5]
The etiology of IGM remains unclear. Autoimmune disease, trauma, lactation, oral contraceptive pill use, and hyperprolactinemia have all been suggested as possible causes.[6] There may also be an association with Corynebacterium, particularly in patients with histological findings of cystic neutrophilic granulomatous mastitis.[7]
Epidemiology
Worldwide, lactational mastitis occurs in 2% to 30% of breastfeeding women.[8] In the United States, the reported incidence is between 7% to 10%.[2][9] The incidence peaks during the first 3 weeks postpartum.[10]
Periductal mastitis is most often found in reproductive-aged females and is almost exclusively associated with tobacco use.[10] Periductal mastitis occurs in 5% to 9% of women worldwide.[11]
IGM is very rare, and its true prevalence is unknown.[12] IGM occurs in parous women, usually within the first 5 years postpartum. Most affected patients report a history of breastfeeding and develop symptoms 6 months to 2 years after the cessation of breastfeeding.[13] The mean age of onset is 32 to 34.[13] Several studies have shown a higher incidence of IGM in Hispanic populations.[14][15][16][12]
Pathophysiology
Lactational mastitis occurs due to the inadequate drainage of milk and the introduction of bacteria. Common scenarios leading to poor milk drainage include infrequent feeding, an oversupply of milk, rapid weaning, illness in the mother or child, and a clogged duct.[3] The inadequately drained milk stagnates, and organisms grow, leading to infection. Bacteria, usually from the infant’s mouth or mother’s skin, possibly enter the milk via cracks in the nipple.[2]
The pathophysiology of periductal mastitis remains unclear. Smoking is thought to play a role by directly or indirectly damaging the ducts leading to subsequent necrosis and infection.[17] Squamous metaplasia is found in patients with this condition, and it is thought that desquamated metaplastic cells may form a plug leading to blockage of the duct and subsequent infection.[18] One recent study showed an upregulation of IFN- γ, and IL-12A in patients with periductal mastitis compared to controls.[5] These are cytokines secreted by T helper 1 cells and play a role in eradicating foreign pathogens. The upregulation of these cytokines suggests that immune responses may play a role in the pathogenesis of periductal mastitis.
The pathophysiology of IGM remains unclear. Still, the most widely accepted theory points to autoimmune destruction initiated by a specific trigger, such as trauma, bacteria, or extravasated milk.[14] This causes leakage of secretions from the ducts into the breast tissue, and inflammatory cells infiltrate, causing a granulomatous response.[19]
Histopathology
A biopsy is not routinely recommended to evaluate periductal mastitis or lactational mastitis.
Non-caseating granulomas with epithelioid histiocytes and multinucleated giant cells in the breast lobules characterize IGM. The classic histologic features of the cystic neutrophilic granulomatous mastitis subtype are non-caseating granulomas with characteristic cystic spaces lined by neutrophils containing gram-positive cocci.[20][21]
History and Physical
Lactational mastitis is often preceded by either engorgement or a focally blocked duct. Patients may give a history of these associated symptoms before developing the classic features of mastitis. Lactational mastitis is characterized by a focal, firm, erythematous, swollen, and painful area of one breast, plus a fever with a temperature ≥100.4 °F (38 °C). Patients often experience systemic symptoms such as chills, myalgias, and malaise.
Features of periductal mastitis include a periareolar or subareolar mass which may be associated with pain and erythema. Patients may present with nipple inversion, a thick nipple discharge, a breast abscess, or draining fistulas.[22]
IGM typically presents with a firm, unilateral breast mass. Other findings may include nipple retraction, skin thickening, axillary adenopathy, ulceration, and abscess formation.[23] Many of these features overlap with the presenting features of breast malignancy, which may, at times, lead to an early misdiagnosis. Patients with IGM can also experience extramammary manifestations, including arthralgias, episcleritis, and skin changes.[24]
Evaluation
The diagnosis of lactational mastitis is made based on history and clinical findings. If there is concern that the patient may have a breast abscess, a breast ultrasound can be obtained. Hypoechoic areas of purulent material will be seen if an abscess is present. A breast milk culture can guide appropriate antibiotic selection for patients with a severe infection unresponsive to initial antibiotic therapy. However, this is not typically necessary. Similarly, blood cultures should be obtained if there is a concern for bacteremia in a patient with severe mastitis. Blood cultures are also not a part of the routine workup.[11]
Periductal mastitis is primarily a clinical diagnosis. If nipple drainage is present, a gram stain and culture should be obtained to identify any associated organisms. An ultrasound or mammography should be ordered if there is a breast mass or concern for malignancy.[11]
Given the clinical features of IGM overlap with those of breast cancer, a breast biopsy must be performed to make this diagnosis. Core needle biopsy or excisional biopsy are acceptable options. Due to the proposed association between hyperprolactinemia and IGM, a prolactin level may be obtained. Ultrasound and mammography alone cannot distinguish IGM from breast malignancy.[13]
Treatment / Management
The initial management of lactational mastitis is symptomatic treatment.[25] Emptying the breasts fully has been shown to decrease the duration of symptoms in patients treated with and without antibiotics. Patients should be encouraged to continue to breastfeed, pump, or hand express.[19][8][9] If the patient stops draining the milk, further stasis occurs, and the infection will progress. Non-steroidal anti-inflammatory drugs (NSAIDs) can be used for pain control. Heat applied to the breast before emptying can help increase milk letdown and facilitate emptying.[25]Cold packs applied to the breast after emptying can help reduce edema and pain.(B3)
If the symptoms of lactational mastitis persist beyond 12 to 24 hours, antibiotics should be administered.[8][9] Antibiotic therapy should be tailored accordingly, with S. aureus as the most common cause. In mild infections without MRSA risk factors, outpatient treatment can be initiated with dicloxacillin or cephalexin. If the patient has a penicillin allergy, erythromycin can be utilized. If the patient has risk factors for MRSA infection, treatment options include trimethoprim-sulfamethoxazole (TMP-SMX) or clindamycin. TMP-SMX should be avoided in women who are breastfeeding infants younger than 1 month and in infants who are jaundiced or premature. If a patient requires hospitalization, empiric treatment with vancomycin should be initiated until culture and sensitivity results return. There are insufficient studies on the appropriate duration of outpatient antibiotic treatment, but most sources recommend a 10 to14 day course.[10](B3)
Periductal mastitis is treated empirically with amoxicillin-clavulanate. Alternative options include dicloxacillin plus metronidazole or cephalexin plus metronidazole. If an abscess is present, ultrasound-guided needle aspiration plus antibiotic therapy is the preferred management choice.[11] Periductal mastitis is often a recurring condition. Surgical excision of the inflamed ducts may be required if a patient has multiple recurrent infections.[26]
The treatment of IGM remains controversial. Current treatment strategies vary broadly, including observation, corticosteroids, immunosuppressants, antibiotics, and surgery.[23] IGM is a benign condition that typically resolves without treatment in an average of 5 months.[23] A recent study showed that the time to resolution of symptoms did not differ between patients managed with medications and those managed with observation and supportive care alone.[23] Surgical excision is an option, but there is a reported 10% recurrence, even with surgical treatment. If IGM is complicated by secondary infection, antibiotics should be chosen based on culture and sensitivity results.
Differential Diagnosis
The differential diagnosis of the 3 forms of mastitis varies significantly. The common differential diagnoses for each are as follows:
Lactational Mastitis
- Breast engorgement
- Clogged duct
- Breast abscess
- Galactocele
- Inflammatory breast carcinoma
Periductal Mastitis
- Duct ectasia
- Breast abscess
- Breast carcinoma
Idiopathic Granulomatous Mastitis
- Breast carcinoma
- Wegener granulomatosis
- Tuberculosis
- Sarcoidosis
- Breast abscess
Prognosis
Most patients with mastitis will recover with appropriate treatment. The recurrence rate for each type of mastitis is as follows:
- Lactational mastitis: 8% to 30% [27][28]
- Periductal mastitis: 4% to 28% [17]
- Idiopathic granulomatous mastitis (IGM): 20% to 78% [29][30]
One study reported that 38% of patients with IGM reported significant scarring, and 29% reported long-term pain.[30]
Complications
One of the most common breastfeeding complications is lactational mastitis resulting in early termination of breastfeeding. The infection of the breast and associated pain are the most commonly cited reasons for early cessation.[25][31] A breast abscess is a complication of lactational mastitis and occurs in 3% to 11% of patients.[32][25] The development of a breast abscess is more common if mastitis is not treated early in its course.
Periductal mastitis and IGM can be complicated by an abscess or fistula formation. Both forms of non-lactational mastitis are associated with recurrence and can lead to scarring and deformity of the breast tissue.
Deterrence and Patient Education
Lactational mastitis frequently develops after a period of incomplete drainage and milk stasis. Educating patients on ways to limit potential stasis to prevent mastitis is crucial. Topics to discuss may include the appropriate feeding frequency and proper infant latching technique. Nipple pain is common in breastfeeding women and may lead to less frequent nursing. This increases milk stasis, thus increasing the patient's risk of developing mastitis. It is essential to counsel patients on decreasing or managing their pain. Patients with lactational mastitis may feel inclined to stop breastfeeding due to discomfort or pain and the concern of passing the infection to their infant. Clinicians should reassure the patient that breastfeeding with mastitis is safe and should recommend the patient continue if desired.[33] If the patient does not wish to continue breastfeeding, she should be counseled on the importance of emptying the breasts and taught alternative methods, such as using a breast pump or manual expression.
In addition to patient education, the education of health care professionals is also essential. One small study showed that some clinicians are misinforming patients with mastitis that they must stop breastfeeding while infected.[28] Not only does this error increase the likelihood of the patient developing an abscess, but it also contributes to the early termination of breastfeeding, eliminating the associated benefits to both the patient and the infant.[33]
Periductal mastitis is found almost exclusively in smokers. Encouraging smoking cessation is essential and may help reduce the risk of recurrent inflammation.
Pearls and Other Issues
Take-Home Points
- One of the most critical considerations in the treatment of lactational mastitis is the need to continue to empty the breasts. Therefore, patients should be encouraged to continue breastfeeding if desired and, if not, to use a breast pump or express by hand.
- Lactational mastitis can be managed conservatively with supportive measures for the first 12 to 24 hours. If symptoms do not improve after this period, antibiotics should be started.
- If symptoms of lactational mastitis do not improve in 24 to 28 hours, consider the possibility of a breast abscess, and obtain a breast ultrasound.
- IGM is a rare condition often mistaken for breast carcinoma. A biopsy must be performed to diagnose this condition and to rule out malignancy.
- The majority of patients with mastitis can be managed as outpatients. Examples in which a patient may require hospitalization include hemodynamic instability, intolerance to oral intake, severe dehydration, and recurrent infection that has failed outpatient management.
Enhancing Healthcare Team Outcomes
Lactational mastitis is a common condition among breastfeeding women. There are several modifiable risk factors discussed in this article, such as feeding too infrequently, the use of certain nipple creams, poor latching techniques, and tight-fitting bras, that predispose women to this condition. Education soon after delivery to raise maternal awareness of these risk factors could decrease mastitis incidence. An interprofessional team approach should be taken when educating postpartum women. Input from physicians, advanced practice practitioners, nursing staff, and lactation consultants should be incorporated in a consolidated effort to help decrease the incidence of lactational mastitis.
While patients with lactational mastitis may seek care from their obstetrician, it is not uncommon for these patients to present to urgent care facilities, emergency departments, or family practice physicians for evaluation. For this reason, healthcare professionals in each of these settings must be aware of the appropriate management. All medical staff caring for patients with mastitis need to be aware of the recommendation that these patients continue to breastfeed and that sudden cessation of breastfeeding increases the risk of abscess formation.[33]
For patients seeking care in the emergency department, where there are often long wait times, pumping or nursing may be necessary during the waiting period. Some hospitals have breast pumps that can be checked out to patients in the emergency department. Emergency department clinicians should know their hospital policy to obtain a breast pump if needed. This can often be coordinated with the lactation consulting or obstetrics teams.
When a physician is unsure whether or not an antibiotic is appropriate to take while breastfeeding, a pharmacist's expertise can be requested to ensure the patient is prescribed a medication that will allow her to continue safely breastfeeding.
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