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ABM ProtocolOpen camera or QR reader andscan code to access this articleand other resources online.Academy of Breastfeeding Medicine Clinical Protocol #36:The Mastitis Spectrum, Revised 2022Katrina B. Mitchell,1Helen M. Johnson,2Juan Miguel Rodrı´guez,3Anne Eglash,4Charlotte Scherzinger,5Irena Zakarija-Grkovic,6Kyle Widmer Cash,7Pamela Berens,8Brooke Miller,9and the Academy of Breastfeeding MedicineAbstractA central goal of the Academy of Breastfeeding Medicine is the development of clinical protocols for managingcommon medical problems that may impact breastfeeding success. These protocols serve only as guidelines for thecare of breastfeeding mothers and infants and do not delineate an exclusive course of treatment or serve as standardsof medical care. Variations in treatment may be appropriate according to the needs of an individual patient. TheAcademy of Breastfeeding Medicine recognizes that not all lactating individuals identify as women. Using gender-inclusive language, however, is not possible in all languages and all countries and for all readers. The position of theAcademy of Breastfeeding Medicine (https://doi.org/10.1089/bfm.2021.29188.abm) is to interpret clinical protocolswithin the framework of inclusivity of all breastfeeding, chestfeeding, and human milk-feeding individuals.Keywords: abscess, breastfeeding, dysbiosis, engorgement, galactocele, lactation, mastitis, phlegmonIntroductionMastitis is a common maternal complication of lac-tation and contributes to early cessation of breast-feeding.1In the past, mastitis has been regarded as a singlepathological entity in the lactating breast.2However, scien-tific evidence now demonstrates that mastitis encompasses aspectrum of conditions resulting from ductal inflammation andstromal edema (Fig. 1). If ductal narrowing and alveolar con-gestion are worsened by overstimulation of milk production,then inflammatory mastitis can develop, and acute bacterialmastitis may follow (Fig. 2). This can progress to phlegmon orabscess, particularly in the setting of tissue trauma from ag-gressive breast massage. Galactoceles, which can result fromunresolved hyperlactation, can become infected. Subacutemastitis occurs in the setting of chronic mammary dysbiosis,with bacterial biofilms narrowing ductal lumens.The pathophysiology, diagnosis, and management of eachcondition in the mastitis spectrum (ductal narrowing, inflam-matory mastitis, bacterial mastitis, phlegmon, abscess, gal-actocele, and subacute mastitis) will be discussed hereunder.Early postpartum engorgement, a distinct condition that canshare some clinical features with mastitis spectrum disorders,will also be reviewed.Note that this protocol now replaces ABM Protocols #4,Mastitis, and #20, Engorgement, which will both be re-tired. ABM Protocols #32 (Management of Hyperlacta-tion)3and #35 (Supporting Breastfeeding During Maternal orChild Hospitalization)4may serve as useful adjuncts to thisprotocol.1Department of Breast Surgery, Ridley-Tree Cancer Center, Sansum Clinic, Santa Barbara, California, USA.2Department of Surgery, East Carolina University Brody School of Medicine, Greenville, North Carolina, USA.3Department of Nutrition and Food Science, Complutense University of Madrid, Madrid, Spain.4Department of Family Medicine and Community Health, University of Wisconsin School of Medicine and Public Health, Madison,Wisconsin, USA.5Department of Gynaecology and Obstetrics at Klinikum Forchheim, Forchheim, Germany.6Department of Clinical Skills, University of Split School of Medicine, Split, Croatia.7Department of Medicine, Tulane University School of Medicine, Southeast, Louisiana Veterans Health Care System, New Orleans,Louisiana, USA.8Department of Obstetrics and Gynecology, University of Texas, Houston, Texas, USA.9Department of Family Medicine, University of Calgary, Calgary, Alberta, Canada.BREASTFEEDING MEDICINEVolume 17, Number 5, 2022ª Mary Ann Liebert, Inc.DOI: 10.1089/bfm.2022.29207.kbm360

Key Information: Pathophysiology of MastitisSpectrum ConditionsGeneral principlesMastitis is inflammation of the mammary gland that mostoften presents in a segmental distribution of ducts, alveoli,and surrounding connective tissue (Fig. 3). Ductal lumenscan be narrowed by edema and hyperemia associated withhyperlactation as well as mammary dysbiosis5(Fig. 2).Mammary dysbiosis, or disruption of the milk microbiome,results from a complex interplay of factors, including ma-ternal genetics and medical conditions, exposure to antibi-otics, use of probiotics, regular use of breast pumps, andCesarean births.6Basic science research has demonstrated that multiple fac-tors contribute to the development of mastitis (Fig. 4).6Theseinclude host factors such as hyperlactation, microbial factorssuch as diversity of the milk microbiome, and medical factorssuch as antibiotic and probiotic use. Milk stasis has beenpostulated to be a potential instigating factor for mastitis,although scientific evidence has not proven a causation. Noevidence exists that specific foods cause mastitis, althoughdietary choices may reflect the underlying health and micro-biome of an individual. The lactating breast is a dynamic glandthat responds to internal and external hormonal stimulation.Compared with a static repository such as the urinary blad-der, the breast requires feedback inhibition to regulate milkproduction. Reducing milk removal may transiently increasepain and erythema from alveolar distention and vascular con-gestion; however, it ultimately prevents future episodes asfeedback inhibitor of lactation (FIL) and other regulatory hor-mones activate and decrease milk production.7Mothers whoexperience persistent high milk production despite eliminatingiatrogenic causes of excessive milk removal may require ad-ditional pharmacological treatment of hyperlactation.3Theseconcepts will be expanded upon throughout this protocol.FIG. 2. Compared with a healthy lactiferous duct (A), ductal inflammation can result in narrowed lumens, stromal edema,dysbiosis, nipple bleb formation, and mastitis (B).FIG. 1. Spectrum of inflammatory conditions in the lac-tating breast.ABM PROTOCOL 361

EngorgementSome symptoms of early postpartum engorgement may besimilar to those of ductal narrowing and early inflammatorymastitis. However, postpartum engorgement that results fromsecretory activation (lactogenesis II) is a distinct clinicalentity related to interstitial edema and hyperemia (Fig. 5).It presents as bilateral breast pain, firmness, and swellingthat usually occurs between days 3 and 5 postpartum.8Onsetmay be as late as 9–10 days, although this is less commonin multiparous mothers.8Cesarean birth is associated withdelayed lactogenesis II and, therefore, delayed presentationFIG. 3. Right breast upper innerquadrant mastitis with ultrasoundshowing hyperemia and edemawithout fluid collection.FIG. 4. Factors that may play a role in the composition of the human milk microbiota and in protecting or predisposing tomastitis.362 ABM PROTOCOL

of engorgement.9If engorgement is managed appropriately,it should not progress to other conditions on the mastitisspectrum such as bacterial mastitis, phlegmon, or galactocele.Ductal narrowing (e.g., ‘‘plugging’’)‘‘Plugging’’ is a colloquial term for microscopic ductalinflammation and narrowing (Fig. 2) that is related to alveolardistension and/or mammary dysbiosis.Ducts in the breast are innumerable and interlacing(Figs. 6–8) and it is not physiologically or anatomically pos-sible for a single duct to become obstructed with a macro-scopic milk ‘‘plug.’’ It should be noted that ultrasound studiesdocumenting a small number of orifices approaching thenipple10reflect limitations of radiographic images as com-pared with histological anatomy.Ductal narrowing presents as a focal area of induration ormore globally congested breast tissue that is tender. It may bemildly erythematous from lymphatic congestion and alveolaredema, and does not have associated systemic symptoms(Fig. 9). This may resolve spontaneously, but patients canexperience transient residual pain. Patients may feel reliefof a ‘‘plug’’ with breastfeeding because this decreases alve-olar distension. However, repeated feeding in an attemptto relieve the ‘‘plug’’ will suppress FIL, increase milk pro-duction, and ultimately exacerbate inflammation and ductalnarrowing. Therefore, physiological breastfeeding and anti-inflammatory measures as described hereunder are mostefficacious. Attempts to extrude a ‘‘plug’’ or milk precipitateby squeezing or aggressively massaging the breast are inef-fective and result in tissue trauma.Inflammatory mastitisWhen ductal narrowing persists or worsens and surround-ing inflammation progresses, inflammatory mastitis develops.Inflammatory mastitis presents as an increasingly erythem-atous, edematous, and painful region of the breast (Fig. 10)with systemic signs and symptoms such as fever, chills, andtachycardia. It should be emphasized that systemic inflam-matory response syndrome may occur in the absence ofinfection.Bacterial mastitisBacterial mastitis represents a progression from ductalnarrowing and inflammatory mastitis to an entity necessi-tating antibiotics or probiotics to resolve. Common organ-isms in lactational mastitis include Staphylococcus (e.g.,S. aureus, S. epidermidis, S. lugdunensis, and S. hominis) andStreptococcus (e.g., S. mitis, S. salivarius, S. pyogenes, andS. agalactiae). Despite the common perception that yeastscause ‘‘candida mastitis,’’ no scientific evidence exists tosupport this diagnosis and sterilization of pump parts or infanttoys is not recommended to ‘‘eradicate’’ yeast.5,11Bacterial mastitis is not a contagious entity and does notpose a risk to the infant nor require an interruption inbreastfeeding. There is no evidence to support poor hygieneas a cause of bacterial mastitis or the need for routine ster-ilization of pumps. Handwashing before milk expression andbasic pump cleaning practices should be followed.Although nipple trauma is associated with mastitis, thedata are limited by confounding and bias.1New evidenceabout the composition of the human milk microbiome dem-onstrates that mastitis is not caused by retrograde spread ofpathogenic bacteria from visible nipple trauma, as bacteriaand fungi identified on the nipple-areolar-complex in thepresence of nipple pain and damage are regularly identifiedin healthy human milk microbiomes.12Infection may notoccur in the event of a low concentration of the pathogen,presence of nonvirulent or weakly virulent strains, presenceof a competitive microbiota, or adequate immunological andnutritional status of the host.13Therefore, two patients whohost the same pathogen may express different levels ofsymptomatology.Bacterial mastitis presents as cellulitis (worsening ery-thema and induration) in a specific region of the breast thatmay spread to different quadrants (Fig. 11). An evaluationby a medical professional should be performed if there arepersistent systemic symptoms (>24 hours) such as fever andtachycardia. In the absence of systemic signs and symptoms,diagnosis should be considered if the breast is not respondingto conservative measures described hereunder. LaboratoryFIG. 5. Day 5 postpartum breast engorgement showingedematous nipple areolar complex and dependent lymphe-dema with overlying erythema.FIG. 6. Cross section of nipple areolar complex with ar-rows demonstrating extremely small interlacing ducts in theretroareolar region.ABM PROTOCOL 363

testing such as C-reactive protein or a white blood cell countare of limited utility in diagnosing bacterial mastitis as theseare markers of inflammation and not specific for infection.PhlegmonPhlegmons are heterogeneous, complex, and ill-definedfluid collections that can occur throughout the body in thesetting of inflammation. Excessive deep tissue massage in thesetting of ductal narrowing and inflammatory mastitis maypropagate phlegmon formation because deep massagepotentiates worsened edema and microvascular injury.14Phlegmon should be suspected with a history of mastitisthat worsens into a firm, mass-like area without fluctuance(Fig. 12). It can be confirmed on ultrasound (Fig. 12).AbscessLactational abscesses represent a progression from bacte-rial mastitis or phlegmon to an infected fluid collection thatnecessitates drainage. Approximately 3–11% of women withacute mastitis will develop an abscess.15Abscess presents as a progressive induration and erythema,and often a palpable fluid collection in a well-defined area ofthe breast (Fig. 13).16The initial systemic symptoms andFIG. 7. Histology image demon-strating functional lobular unitswith small central duct, surround-ing fat, and fibrous stroma (con-nective tissue).FIG. 8. Histology image demon-strating innumerable small ductsdraining into larger ductal systemsthat have complex architecture.364 ABM PROTOCOL

fever may resolve as the body walls off the infectious pro-cess, or may resolve and then recur. Alternatively, symptomsmay continue to worsen until the infected fluid collectionis drained. Although the diagnosis of abscess is often made byhistory and clinical examination, ultrasound also may beutilized (Fig. 14).17Galactocele and infected galactoceleA galactocele develops when ductal narrowing obstructsthe flow of milk to the extent that a significant volume ofobstructed milk collects in a cyst-like cavity.18Galactocelescan range in size from small (1–2 cm) to very large (>10 cm).Galactoceles present as a moderately firm mass thatgradually or rapidly increases in size over time. The size mayfluctuate throughout the day, with a temporary decrease afterbreastfeeding. It may be uncomfortable, but is generally notas overtly painful as an abscess and does not have associatederythema or systemic symptoms unless it becomes infected(Fig. 15). Ultrasound will show a simple or loculated cysticfluid collection (Fig. 16). On occasion, image-guided aspi-ration may be utilized to confirm the diagnosis.Recurrent mastitisThere is no consensus on the definition of recurrent mas-titis. Patients may describe having mastitis symptoms such asfever, breast redness, breast swelling, and/or breast pain thatoccur every 2–4 weeks, or less often. Risk factors includewaxing and waning episodes of hyperlactation, dysbiosis,inadequate treatment of prior mastitis, and failure to addressthe underlying etiology of prior episodes.Subacute mastitisSubacute mastitis occurs when ductal lumens become nar-rowed by bacterial biofilms in the setting of chronic mammarydysbiosis.5Dysbiosis is defined as changes in the quantitativeand qualitative composition of a host microbiome that con-tribute to inflammatory disease both acutely and chronically. Asin other organs, when the mammary microbiome loses bacterialdiversity and the number of anti-inflammatory organisms de-clines, an increase in pathogenic bacteria occurs.19,20Under physiological conditions, coagulase-negative Sta-phylococci (CoNS) and viridans Streptococci (i.e., S. mitisand S. salivarius) form thin biofilms that line the epitheliumof the mammary ducts, allowing a normal milk flow.21In thesetting of dysbiosis, these species proliferate and functionunder opportunistic circumstances whereby they are able toform thick biofilms inside the ducts, inflaming the mammaryepithelium and forcing milk to pass through an increasinglynarrower lumen (Fig. 17). CoNS and viridans Streptococcido not produce toxins responsible for acute bacterial masti-tis; therefore, systemic symptoms are uncommon and localbreast symptoms are milder than in acute mastitis.With subacute mastitis, patients may report a history ofpreviously treated acute bacterial mastitis. Other pertinenthistory includes Cesarean birth, exclusive pumping, nip-ple shield use, and other circumstances that alter the milkmicrobiome.6Patients may have needle-like, burning breastpain, nipple blebs, recurrent areas of induration or congestion,and may have unresolved hyperlactation.22Sterile milk cul-ture and sensitivities can be performed23as noted hereunder.RecommendationsFor each recommendation, the quality of evidence (levelsof evidence 1, 2, and 3) and the strength of recommendation(A, B, and C) are noted as defined by the strength of rec-ommendation taxonomy criteria.24Management of mastitis spectrum disorders includesgeneral strategies that apply to the entire spectrum, as well ascondition-specific interventions. Prompt and effective treat-ment will halt progression in the spectrum. Many of thesemeasures provide not only treatment, but prevention as well.Spectrum-wide management strategies will be delineatedfirst, followed by specific recommendations for particularFIG. 9. Patient with unilateral left breast ‘‘plug’’ in upperouter quadrant who worsened milk obstruction by repeat-edly pumping.FIG. 10. Patient with early in-flammatory mastitis. Lymphaticcongestion is noted by arrow. Thepatient was treated with ice, ibu-profen, acetaminophen, and feed-ing first off the left, less congestedbreast first to avoid overstimulationof the affected right breast. Thepatient’s symptoms resolved within48 hours.ABM PROTOCOL 365

conditions (ductal narrowing, inflammatory mastitis, bacterialmastitis, phlegmon, abscess, galactocele, subacute mastitis,and recurrent mastitis). Recommendations for management ofearly postpartum engorgement are also included hereunder.Spectrum-wide recommendations1. Anticipatory guidance and behavioral interventionsa. Reassure mothers that many mastitis symptoms willresolve with conservative care and psychosocial sup-port.A Swedish study noted that most women with in-flammatory mastitis had complete resolution ofsymptoms without need for antibiotics or other inter-ventions. The authors attributed this finding to a focuson symptomatic control, appreciation of the physio-logical anti-inflammatory response, and regular com-munication between patient and clinician25(Fig. 10).Support patients in continuation of breastfeeding andascertain what resources they may need to preventearly weaning. Assist mothers in identifying ways todecrease stress, increase opportunities to rest, and helpresolve early signs of inflammatory mastitis. Fourth-trimester care programs represent a holistic approachto postpartum care, including mental health, psycho-social needs, and breastfeeding counseling.26Level of evidence: 3. Strength of recommendation: C.b. Educate patients on normal breast anatomy andpostpartum physiology in lactation.Many patients experience breast fullness or palpatenormal lactational glandular tissue and misinterpretthis as ‘‘plugging.’’ They should be reassured thatlactating breasts can feel ‘‘lumpy’’ and even painful attimes. Although this is uncomfortable, it is not ab-normal. Patients should be educated about earlypostpartum hormonal shifts and a low estrogen statethat predisposes patients to sweating and hot flashesthat may mimic fevers. In addition, patients should bereassured that infection does not develop in the periodof several hours. The pain and redness they may ex-perience in mornings after a long stretch of sleeprepresents alveolar distention, edema, and inflamma-tion rather than infection.Level of evidence: 3. Strength of recommendation: C.c. Feed the infant on demand, and do not aim to‘‘empty’’ breasts.FIG. 12. Clinical appearance ofleft breast upper inner quadrantphlegmon. Ultrasound showing in-distinct fluid collection with sur-rounding hyperemia and edema.FIG. 11. Bacterial mastitis that progressed from earlyinflammation in the inner quadrant to all quadrants beingaffected. This patient also pumped and continually fed theinfant on the right breast in an attempt to prevent ‘‘milkstasis.’’ This approach resulted in worsened ductal inflam-mation and bacterial overgrowth as well as milk obstruction.366 ABM PROTOCOL

Milk volume depends on a feedback mechanismwhereby increased milk removal increases produc-tion.7Overfeeding from the affected breast or‘‘pumping to empty’’ perpetuates a cycle of hy-perlactation and is a major risk factor for worseningtissue edema and inflammation (Fig. 18). Mothers canhand express small volumes of milk for comfort untiltheir milk production downregulates to match theinfant’s needs.27Mothers using breast pumps shouldexpress only the volume their infant consumes.In some instances, in which the retroareolar regionis so edematous and inflamed that no milk is ex-pressible by infant breastfeeding or hand expres-sion, the mother should not continue to attemptfeeding from the affected breast during the acutephase (Fig. 19). She can feed from the contralateralbreast and return to feeding from the affected breastwhen edema and inflammation subsides. Edemamay resolve more quickly with ice and lymphaticdrainage. She should be counseled that a decrease inmilk production is expected, but can later be aug-mented.No evidence exists to support ‘‘dangle feeding’’(i.e., feeding an infant on the floor with the motherhovering above) or other unsafe infant positions.Patients may consider safe variations on standardfeeding positions, with the understanding that thismay improve comfort. However, this does not ad-dress underlying inflammation.Levels of evidence: 2–3. Strength of recommendation:C.d. Minimize breast pump usage.Mechanical breast pumps stimulate breast milk pro-duction without physiologically extracting milk as aninfant will. Pumping does not provide the opportu-nity for bacterial exchange between the infant’s mouthand mother’s breast, and may, therefore, predispose todysbiosis.6Breast pumps also can cause trauma tobreast parenchyma and the nipple areolar complex ifimproper flange sizes are used, suction is too high,or the mother is pumping for an excessive durationof time. Milk expression should be limited to whenmother is separated from her infant or requires pump-ing for other medically indicated reasons for herself orher infant. Women should not be instructed to expressand discard their milk, as bacterial mastitis is not acontraindication to breastfeeding. Women using abreast pump should express milk at a frequency andvolume that mimics physiological breastfeeding.Levels of evidence: 2–3. Strength of recommendation:C.e. Avoid the use of nipple shields.Available evidence does not support the use ofnipple shields. Neither safety nor effectiveness hasbeen demonstrated. Similar to pumping, nippleFIG. 14. Ultrasound image showing fluid collection(black) with needle entering (white).FIG. 13. Patient with right breastupper outer quadrant abscess whounderwent office drainage withPenrose drain stent that was re-moved after 3 days. At 1 weekfollow-up, the right breast was re-solved and the 1 mm stab incisionsite closed.ABM PROTOCOL 367

shields represent nonphysiological breastfeedingand result in inadequate breast milk extraction.28Infants often passively drink milk from the shieldrepository without latching to the parenchyma ofthe breast.Level of evidence: 3. Strength of recommendation:C.f. Wear an appropriately fitting supportive bra.Lactating breasts are highly vascular and requiresupport to avoid dependent lymphedema as well asprogressive back and neck pain.Level of evidence: 3. Strength of recommendation:C.g. Avoid deep massage of the lactating breast.Deep massage causes increased inflammation, tissueedema, and microvascular injury. Avoid electrictoothbrushes and other commercial vibrating ormassaging devices. A systematic review concludedthat although breast massage may reduce pain, itshould not be recommended as standard of carebecause it requires extensive training to masteratraumatic approach.29The most successful tech-nique approximates manual lymphatic drainagewith light sweeping of the skin rather than deeptissue massage.30,31It should be noted that gentlecompressions during breast pump usage, oftentermed ‘‘hands on pumping,’’ provide an effectsimilar to hand expression and is safe if excessivemanual force is avoided.Levels of evidence: 1–2. Strength of recommenda-tion: B.h. Avoid saline soaks, castor oil, and other topicalproducts.Mastitis is inflammation and/or infection in a deeporgan space, and should be managed as such.Topical products such as castor oil will not treatthis condition and may in fact cause tissue dam-age32particularly if they are combined withmassage.14Silicone breast pumps filled with Ep-som salt can macerate skin33and further contrib-ute to localized hyperemia and edema, and shouldbe avoided. Published evidence and best practicefor general wound care do not support the use ofsaline soaking for pain or nipple trauma. Princi-ples of wound management include handling tis-sue delicately to minimize further trauma andconsideration of ointments and dermal matrices toenhance wound closure.33Level of evidence: 3. Strength of recommendation:C.i. Avoid routine sterilization of pumps and householditems.Mastitis is not contagious and does not result fromunhygienic practices. Pump parts should becleaned appropriately after each use, but routinesterilization of pumps and other household itemsis not necessary to prevent mastitis.34Avoidcleaning of nipple as this may cause skin macer-ation and pain. Ascending infection is not sup-ported by the highly vascular nature of nipplephysiology and anatomy.35Similar to other opensites of trauma in the body (e.g., tracheostomiesand gastric tube entrance sites), external commu-nication prevents deep tissue infection rather thanpromotes it.FIG. 16. Mammogram showinggalactocele adjacent to nipple are-olar complex and ultrasoundshowing septation within galacto-cele.FIG. 15. Galactocele that was repeatedly drained with aneedle and subsequently became infected.368 ABM PROTOCOL

Level of evidence: 3. Strength of recommendation:C.2. Medical interventionsa. Decrease inflammation and pain.Ice and nonsteroidal anti-inflammatory drugs(NSAIDs) can reduce edema and inflammationand provide symptomatic relief (Figs. 10 and 19),and acetaminophen/paracetamol can provide anal-gesia.36For example, ice can be applied every houror more frequently if desired. Ibuprofen can bedosed 800 mg every 8 hours37and acetamino-phen/paracetamol 1,000 mg every 8 hours38in theacute setting.Although heat will vasodilate and may worsensymptoms, it also may provide comfort for somepatients.39The use of warm showers and antipy-retics did not improve mastitis outcomes in a ran-domized controlled trial.25Sunflower or soy lecithin 5–10 g daily by mouthmay be taken to reduce inflammation in ducts andemulsify milk.22,40Levels of evidence: 1–3. Strength of recommenda-tion: C.b. Treat associated nipple blebs and avoid unroofing.If a nipple bleb, which represents ductal inflam-matory cells propagating to the surface and lodging(Figs. 2 and 20), is present, do not unroof the bleb asthis will cause trauma and further luminal narrow-ing. Oral lecithin and application of a topicalmoderate potency steroid cream such as 0.1% tri-amcinolone may be used to reduce inflammation onthe surface of the nipple.22This is safe withbreastfeeding and can be wiped off with a tissue ortowel before feeding the infant.41Levels of evidence: 2–3. Strength of recommenda-tions: C.c. Treat hyperlactation, or breast milk ‘‘oversupply.’’Hyperlactation predisposes patients to luminalcongestion and inflammation, which in turn facili-tates mammary dysbiosis. This may potentiate avicious cycle, as dysbiosis is a cause of ductalnarrowing and inflammation. See ABM Protocol 32,Management of Hyperlactation.3Level of evidence: 2. Strength of recommendation:C.FIG. 18. Patient with history ofright breast mastitis who was in-structed to pump every 2 hours to‘‘keep the breast empty.’’ This re-sulted in severe upregulation ofmilk production in her right breastand a continued cycle of mastitis.After being instructed to feed fromthe less full (left) breast first, shedownregulated the right breast andexperienced no recurrent episodesof mastitis.FIG. 17. Electron microscopy showing normal mam-mary ducts compared with mammary ducts with biofilmformation.ABM PROTOCOL 369

d. Utilize therapeutic ultrasound.Therapeutic ultrasound, or TUS, uses thermal energyto reduce inflammation and relieve edema. TUS maybe an effective treatment for conditions arising in themastitis spectrum.42TUS can be performed under thesupervision of a trained physician or physiotherapiston a daily basis until relief is achieved. The breasttreatment setting is 1 MHz, intensity 2.0 W/cm2for5 minutes.43If a patient has persistent symptomsdespite several days of treatment, health care pro-viders should consider additional investigations.Levels of evidence: 2–3. Strength of recommendation:C.e. Reserve antibiotics for bacterial mastitis.Use of antibiotics for inflammatory mastitis disruptsthe breast microbiome and increases the risk ofprogression to bacterial mastitis. Furthermore,nonselective use of antibiotics promotes develop-ment of resistant pathogens. Prophylactic antibioticshave not been shown to be effective in the pre-vention of mastitis.44It should be noted that manyantibiotics and antifungal medications have anti-inflammatory properties, and this may explain whywomen experience relief when taking these.Level of evidence: 2. Strength of recommendation:B.f. Consider probiotics.Data regarding probiotics are mixed.44–47A sys-tematic review suggested that probiotics may beeffective for both treatment and prevention of mas-titis, but a strong recommendation could not bemade due to limitations of the studied trials.47IfFIG. 20. Examples of differentpresentations of nipple blebs.FIG. 19. Ducts can becomenarrowed secondary to alve-olar distention and conges-ted vessels and lymphatics.Ice and decreased removalof breast milk reduce duc-tal narrowing and breastswelling.370 ABM PROTOCOL

utilized, the probiotic should contain Limosilacto-bacillus fermentum (formerly classified as Lactoba-cillus fermentum) or, preferably, Ligilactobacillussalivarius (formerly classified as Lactobacillus sal-ivarius) strains.48,49Note that only selected strainsof these bacterial species may be effective againstmastitis pathogens. Therefore, clinical trial out-comes cannot be generalized to an entire species inthe same way that antibiotics may be efficaciousagainst one strain of a pathological bacteria but notanother.Levels of evidence: 1–2. Strength of recommendation:B.g. Evaluate for perinatal mood and anxiety disorders(PMADs).Women with a history of anxiety and depressionexperience higher rates of mastitis symptoms,50andPMADs are increased in any patient experiencingbreastfeeding complications. Although any clini-cians contacting postpartum patients should screenfor PMADs,26particular attention should be paid topatients feeling defeated and/or withdrawn as aresult of challenges with breastfeeding. Further-more, patients who express significant worry aboutpotential recurrence and are unable to stop pumpingdespite recommendations may be suffering fromanxiety. Extreme pain out of proportion to exammay also point to alterations in sensitivity to stim-ulation as a result of PMADs and, therefore, shouldbe considered in the differential diagnosis.51Care-ful exploration of Dysphoric Milk Ejection Reflexand/or nursing aversion may also be warranted ifthe patient does not report traditional symptoms ofPMADs.52Level of evidence: 3. Strength of recommendation: C.Condition-specific recommendationsa. Recommendations for postpartum engorgement inlactogenesis IIMinimize intravenous fluids during labor, as inter-stitial fluid accumulation exacerbates edema andengorgement.53Promote ‘‘rooming in’’ to allow physiologicalbreastfeeding and avoidance of pumping.54Instruct mothers on hand expression to relievesymptoms and provide breast milk for infants whomay not transfer milk effectively or are separatedfrom their mothers.55Perform reverse pressure softening of the areola,56and manual pump or hand expression to removesmall volumes of milk before infant latch and facil-itate physiological milk transfer.FIG. 21. Technique of lymphatic drainage.ABM PROTOCOL 371

Consider lymphatic drainage to alleviate interstitialedema31(Fig. 21).Consider ice for symptomatic relief. Studies have notdemonstrated cabbage leaves to be more effectivethan ice,57suggesting that the therapeutic benefit isrelated to vasoconstriction from cold rather than aproperty of cabbage itself. Importantly, cabbage maycarry Listeria bacteria.Levels of evidence: 2–3. Strength of recommenda-tions: B–C.b. Recommendations for ductal narrowing and inflam-matory mastitisFollow spectrum-wide recommendations mentionedearlier.c. Recommendations for bacterial mastitisAntibiotic selection, dosage, and duration for bacte-rial mastitis are outlined in Box 1.It is safe for children to consume milk from a breastwith bacterial mastitis.58Routine hospital admission and IV antibiotics are notnecessary unless known multidrug-resistant organ-ism (MDRO) or clinical presentation mandates (e.g.,evidence of severe sepsis and inability to tolerateoral medication or fluid). Of note, some MDRO maybe treatable using oral antibiotics. Antibiotic choiceshould be driven by culture data or local anti-biogram. If hospital admission is necessary, motherand infant should be kept rooming in together andallowed to continue to breastfeed on demand. ABMProtocol #35, Supporting Breastfeeding During Ma-ternal or Child Hospitalization, refers to other rec-ommendations in detail.4Consider intravenous fluid administration if patient’soral intake of fluids is suboptimal as this may alle-viate tachycardia and improve symptomatology.If there is no symptomatic improvement after 48hours of first-line therapy, consider a milk culture toevaluate for resistant and/or less common pathogenssuch as methicillin-resistant Staphylococcus aureus(MRSA).58Consider local susceptibility and resis-tance patterns and proceed to empiric therapy. Othersituations in which to consider early milk cultureinclude mothers expressing breast milk for an im-munocompromised infant in the neonatal intensivecare unit, health care workers in areas with a highprevalence of MRSA, and patients with recurrentinfections.Data regarding the role of probiotics in bacterial mastitiscontinue to emerge. Probiotics have been shown not toalter composition of human milk microbiome.44–47Levels of evidence: 2–3. Strength of recommenda-tions: C.d. Recommendations for phlegmonLactational phlegmon may require extended antibi-otics for complete resolution, but cases should beconsidered individually.14A phlegmon may coalesce into a drainable abscessand, therefore, patients should be followed carefullyfor this development. Interval examination and im-aging is warranted until complete resolution.14Level of evidence: 2. Strength of recommendations:C.FIG. 22. Options for drainage oflactational fluid collections.Box 1. Empiric Antibiotic Management58,74First lineDicloxacillin or flucloxacillin 500 mg QID for 10–14daysWhere dicloxacillin and flucloxacillin are not available,cloxacillin can be used alternatively; however, oralbioavailability is more variable with cloxacillin.75Alldrugs have low Relative Infant Dose of the drug.76Cephalexin 500 mg QID for 10–14 daysBroader coverage including gram negative rods; doesnot need to be taken separately from mealsSecond lineClindamycin 300 mg four times daily for 10–14 daysTrimethoprim-sulfamethoxazole DS BID for 10–14daysB Not recommended for mothers of children withG6PD deficiency. Use with caution in mothers withpremature infants or infants withhyperbilirubinemia, especially under 30 days old.77372 ABM PROTOCOL

e. Recommendations for abscessDrain the abscess to achieve source control. Needleaspiration with fluid culture and sensitivity is oftenrecommended as the first-line intervention for lacta-tional abscess.59However, patients most often requirerecurrent aspirations for definitive resolution. Repeatedaspirations may be stressful and discouraging for thepatient, and risk breastfeeding discontinuation.60–62Drain placement as the initial intervention shouldbe considered for definitive management at thetime of the index procedure. Office drainage isdemonstrated in published videos63,64and illus-trated in Figure 13. Patients also can be referred tointerventional radiology for drain placement.Drains or skin stents should be placed to gravityrather than suction (Fig. 22). If formal drain is notavailable, adaptations using supplies such as Foleycatheters or glove fingers can be used based onlocal resources. Strictly avoid vacuum-assistedwound devices on a lactating breast.After aspiration or drain placement, mothers shouldcontinue breastfeeding from the affected breast. Milkfistula rate is <2%, but lactation must be managedappropriately and hyperlactation treated if present.65Antibiotic duration is commonly 10–14 days58;however, a shorter course may be appropriate if thereis rapid resolution of surrounding cellulitis.Tissue inflammation and phlegmonous changes maytake several weeks to resolve and patients may feelthe presence of a small mass-like area. They shouldundergo interval examination and imaging to ensureresolution.14Levels of evidence: 2–3. Strength of recommenda-tions: C.f. Recommendations for galactocele and infectedgalactoceleFor symptomatic galactoceles, drainage isrecommended for symptom relief, confirmation ofdiagnosis, and to decrease mass effect to facilitatelatch. Aspiration almost always results in incompletedrainage and/or recurrence, and repeated aspirationsrisk converting a sterile galactocele into an infectedgalactocele. Therefore, drain placement as describedearlier is recommended.An infected galactocele requires drainage as well asantibiotics (Fig. 15).66Level of evidence: 3. Strength of recommendations:C.g. Recommendations for recurrent mastitisExamine patients and obtain milk culture to establish adiagnosis of true recurrent mastitis, rather than treatingempirically. Breast milk culture23(Box 2) can identifyand provide sensitivities of uncommon pathogens andresistant bacteria. For example, although CoNS are com-monly present in breast milk, they have also beenidentified as opportunistic pathogens in mastitis.67MRSA and resistant CoNS will not respond to typicalantibiotics used for acute mastitis such as dicloxacillinor cephalexin.Ensure resolution of bacterial mastitis, as earlier,with follow-up examination of patients.Evaluate breastfeeding and/or pumping for potentialrisk factors for mastitis (e.g., excessive massage andunnecessary pumping).Consider daily probiotic use with L. fermentum or,preferably, L. salivarius for prevention,48,49recog-nizing the limitations of different strains of the samespecies having different efficacies.Prophylactic antibiotics have not been shown to beeffective in the prevention of mastitis and may selectantibiotic-resistant strains.44Multiple recurrences in the same location warrants radi-ology evaluation to rule out an underlying mass or otherabnormality such as granulomatous mastitis.68Inflam-matory breast cancer is an aggressive subtype of malig-nant tumors that presents with progressive erythema,breast retraction, and peau d’orange appearance of thebreast. Any concern for inflammatory breast cancer war-rants urgent referral to breast surgery and oncology.69Levels of evidence: 1–3. Strength of recommenda-tions: B–C.h. Recommendations for subacute mastitisIndividual mammary microbiomes have differentenvironmental thresholds at which opportunisticbacterial pathogens become symptomatic. Further,milk culture may not grow a dominant organism.Therefore, treatment should be individualized basedon clinical history and level of suspicion for subacutemastitis.70,71Antibiotics in the macrolide class mayhave the best efficacy in this clinical scenario due tothe intracellular mechanism of action, though morestudies are needed.72Probiotics containing L. salivarius or L. fermentumstrains represent a treatment option, although morestudies are required.48,49Levels of evidence: 2–3. Strength of recommenda-tions: B–C.SummaryOverall, conditions occurring in the mastitis pathophysi-ological spectrum can be prevented and treated by reducingiatrogenic interventions and utilizing simple managementprinciples such as ice, NSAIDs, and physiological breast-feeding. Attention should be given to appropriate treatmentBox 2. How to Perform a Sterile BreastMilk Culture1. Clean the nipple and areola: Both a topical antisepticsolution and washing with warm water and soap withair-drying have been proposed. There are no data todetermine which is better to remove skin flora whilepreserving the integrity of the nipple and areolar skin.2. Use sterile gloves to express milk.3. Collect 5–10 mL milk in a sterile container.4. No contact should be made between nipple and sterilecontainer.5. Send as ‘‘body fluid culture’’ rather than ‘‘woundculture.’’ABM PROTOCOL 373

of hyperlactation as an primary underlying risk factor formastitis. Similarly, given the importance of a healthy breastmilk microbiome in preventing mastitis, risk factors for dys-biosis should be addressed. Understanding the pathophysi-ology of ductal narrowing and inflammation allows cliniciansto select targeted effective treatments for mastitis.Traditional recommendations to augment milk removal tocounteract milk stasis and to massage breast tissue to relieveductal obstruction from milk ‘‘plugs’’ lack physiologicalvalidity. Frequent stimulation of breasts with congested al-veolar cells worsens hyperemia and edema, causing increa-sed pain, swelling, and redness. This not only worsens painand edema, but also decreases the ability of an infant to obtainan atraumatic latch and effectively withdraw milk from thebreast. Frequent pumping also disrupts the milk microbiome,potentiating the development of mammary dysbiosis andincreasing the risk for bacterial mastitis. In addition, massageof the mammary gland causes capillary injury and tissuenecrosis, and is a primary risk factor for phlegmon andabscess development.Areas for Future ResearchClinical studies on mastitis and related disorders are lim-ited by study design and confounding factors. For example,nipple trauma appearing to be a cause of mastitis likelyrepresents an association rather than a causation. Nippletrauma is extremely frequent in hyperlactation, which is a riskfactor for mastitis. Future studies should carefully control forpotential confounding factors as well as explore diversecultures and practices throughout the world. In addition,higher quality studies are needed to determine precise rec-ommendations regarding antibiotics as the presence of evensmall quantities of antibiotics in human milk alters thediversity and resilience of the human milk microbiome.73Because antibiotics are often prescribed through telephonetriage in many countries, studies to clarify prevalence ofbacterial mastitis as opposed to engorgement and/or inflam-matory mastitis are necessary. The use of probiotics warrantsfurther research as well. As women in the peripartum periodare at their lifetime highest risk for developing an anxiety ormood disorder, the distinction between symptoms of moodand anxiety disorders versus mastitis should also be explored.Disclosure StatementJ.M.R. has been the PI of research projects and clinicalassays funded by Puleva/Biosearch Life (Granada, Spain) orNutricia (Utrecht, The Netherlands), involving the charac-terization, safety, and efficacy of probiotic strains for themastitis target. He and his research group have never receivedany payment or royalty related to the commercialization ofprobiotic strains.Funding InformationNo funding was received for this article.References1. Wilson E, Woodd SL, Benova L. Incidence of and riskfactors for lactational mastitis: A systematic review. J HumLact 2020;36:673–686.2. Kvist LJ. Toward a clarification of the concept of mastitisas used in empirical studies of breast inflammation duringlactation. J Hum Lact 2010;26:53–59.3. Johnson HM, Eglash A, Mitchell KB, et al. ABM clinicalprotocol #32: Management of hyperlactation. BreastfeedMed 2020;15:129–134.4. Bartick M, Herna´ndez-Aguilar MT, Wight N, et al. ABMclinical protocol #35: Supporting breastfeeding during mater-nal or child hospitalization. Breastfeed Med 2021;16:664–674.5. Jimenez E, Arroyo R, Cardenas N, et al. Mammary can-didiasis: A medical condition without scientific evidence?PLoS One 2017;12:e0181071.6. Ferna´ndez L, Pannaraj PS, Rautava S, et al. 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62. Christensen AF, Al-Suliman N, Nielson KR, et al.Ultrasound-guided drainage of breast abscesses: Results in151 patients. Br J Radiol 2005;78:186–188.63. Mitchell K. In-office drainage of lactational abscesses:Utilization of stab incision and penrose drain. Presented atthe American Society of Breast Surgeons 22nd AnnualMeeting, April 30, 2021.64. Kornfeld H, Johnson A, Soares M, et al. Management ofinfected galactocele and breast implant with uninterruptedbreastfeeding. Plast Reconstr Surg Glob Open 2021;9:e3943.65. Johnson HM, Mitchell KB. Low incidence of milk fistulawith continued breastfeeding following radiologic andsurgical interventions on the lactating breast. Breast Dis2021;40:183–189.66. Ghosh K, Morton MJ, Whaley DH, et al. Infected galac-tocele: A perplexing problem. Breast J 2004;10:159.67. Arroyo R, Martı´n V, Maldonado A, et al. Treatment ofinfectious mastitis during lactation: Antibiotics versus oraladministration of lactobacilli isolated from breast milk.Clin Infect Dis 2010;50:1551–1558.68. Mitchell KB, Johnson HM, Eglash A. ABM clinical pro-tocol #30: Breast masses, breast complaints, and diagnosticbreast imaging in the lactating woman. Breastfeed Med2019;14:208–214.69. Dawood S, Merajver SD, Viens P, et al. International expertpanel on inflammatory breast cancer: Consensus statementfor standardized diagnosis and treatment. Ann Oncol 2011;22:515–523.70. Anderson PO. Drugs in lactation. Pharm Res 2018;35:45.71. Geng N, Liu K, Lu J, et al. Autophagy of bovine mammaryepithelial cell induced by intracellular Staphylococcus au-reus. J Microbiol 2020;58:320–329.72. Parnham MJ, Erakovic Haber V, Giamarellos-BourboulisEJ, et al. Azithromycin: Mechanisms of action and theirrelevance for clinical applications. Pharmacol Ther 2014;143:225–245.73. Soto A, Martin V, Jimenez E, et al. Lactobacilli and bifi-dobacteria in human breast milk: Influence of anti-biotherapy and other host and clinical factors. J PediatrGastroenterol Nutr 2014;59:78–88.74. Mitchell K, Johnson H. Breast conditions in the breast-feeding mother. In: Breastfeeding: A Guide for the MedicalProfession, 9 ed., Lawrence R, Lawrence R, eds. Elsevier,2021, pp. 572–593.75. Nauta EH, Mattie H. Dicloxacillin and cloxacillin: Phar-macokinetics in healthy and hemodialysis subjects. ClinPharmacol Ther 1976;20:98–108.76. Hale T. Hale’s Medications & Mother’s Milk: A Manual ofLactational Pharmacology, 19th ed. New York, NY: Springer,2021.77. Drugs and Lactation Database (LactMed). Bethesda, MD:National Library of Medicine (US), 2006. Trimethoprim-sulfamethoxazole. Updated 2021. Available at https://www.ncbi.nlm.nih.gov/books/NBK501289/ (accessedSeptember 2, 2021).ABM protocols expire in 5 years from the date of publica-tion. Content of this protocol is up to date at the time of pub-lication. Evidence-based revisions are made within 5 years orsooner if there are significant changes in the evidence.Katrina B. Mitchell, MD, FACS, lead authorHelen M. Johnson, MDJuan Miguel Rodrı´guez, PhDAnne Eglash, MD, FABMCharlotte Scherzinger, MDIrena Zakarija-Grkovic, MD, FRACGP, PhD, FABMKyle Widmer Cash, MDPamela Berens, MD, FACOG, FABMBrooke Miller, MD, CCFPThe Academy of Breastfeeding Medicine ProtocolCommittee Members:Elizabeth Stehel, MD, ChairLawrence Noble, MD, FABM, Translations ChairMelissa C. Bartick, MD, MS, FABMSarah Calhoun, MDLaura Kair, MD, MAS, FABMSusan Lappin, MD, FABMIlse Larson, MDYvonne LeFort, MD, FABMNicole Marshall, MD, MCRKatrina B. Mitchell, MDSusan Rothenberg, MD, FABMTomoko Seo, MD, FABMGina Weissman, DMDNancy Wight, MD, FABMLori Feldman-Winter, MD, MPHAdora Okogbule-Wonodi, MDMichal Young, MD, FABMDeena Zimmerman, MD, MPHFor correspondence: abm@bfmed.org376 ABM PROTOCOL