01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Duct ectasia and periductal mastitis overlap clinically but are not interchangeable. Ectasia often reflects shortening and dilatation of subareolar ducts, with inspissated secretions causing green or brown multiduct discharge and sometimes inversion. Periductal mastitis affects the larger ducts beneath the nipple, where squamous metaplasia and keratin obstruction contribute to inflammation, bacterial infection, abscess and a fistulous track to periareolar skin.
The immediate task is to distinguish a non-infected discharge syndrome from cellulitis or abscess and to test whether the benign explanation accounts for every finding. Ultrasound can show dilated ducts or a collection and guide aspiration. Antibiotics follow local microbiology and allergy information, but source control is essential for pus. Recurrent disease needs smoking support and breast-surgical planning because repeated incision or short antibiotic courses can produce scarring without addressing the pathological duct.
Key points
- Duct ectasia describes dilated subareolar ducts containing secretions and commonly causes thick multiduct discharge, nipple retraction or a tender retroareolar lump.
- Periductal mastitis is inflammation around major ducts, is strongly associated with smoking and may progress to recurrent periareolar abscess or mammary duct fistula.
- Pain, erythema and fluctuation require ultrasound to identify a drainable collection; systemic illness requires urgent physiological assessment and same-day surgical input.
- New unilateral nipple retraction, blood-stained discharge, an irregular mass or failure to improve must be investigated for malignancy rather than attributed indefinitely to benign duct disease.
- Drainage provides source control for an abscess and pus culture guides antibiotic refinement; repeated antibiotics alone cannot cure an established collection or chronic tract.
- Smoking cessation, control of acute infection and specialist discussion of diseased-duct excision are central when periareolar episodes recur.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Involutional duct change
With ageing, major subareolar ducts may shorten and dilate, allowing lipid-rich secretions and cellular debris to accumulate and provoke surrounding inflammation.
Smoking-associated duct injury
Smoking is strongly linked to squamous metaplasia and keratin plugging of major ducts, promoting rupture, bacterial infection, abscess and fistula formation.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Secretion stasis
Inspissated contents distend retroareolar ducts and may discharge through several nipple openings or leak into surrounding tissue.
- 2Duct rupture and abscess
Obstruction and epithelial injury permit rupture; keratin, bacteria and secretions trigger periductal inflammation that can liquefy into an abscess.
- 3Fistulous persistence
An abscess that drains to periareolar skin may epithelialise into a tract connecting the diseased duct to the surface, enabling recurrent infection.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Thick green, brown or creamy fluid from more than one duct with subareolar tenderness supports ectasia, especially around or after menopause; a dominant lesion must still be excluded.
Localised warmth, pain and a tender subareolar mass suggest periductal inflammation. Fluctuation, skin thinning or pointing indicates an abscess requiring urgent imaging and drainage.
A recurrent draining opening near the areolar edge after previous abscess is characteristic. Alternating closure and discharge reflects a persistent duct-skin tract, not poor hygiene.
New fixed inversion, eczematous change, blood-stained single-duct discharge, irregular mass, nodes or absent response to infection treatment requires renewed triple assessment.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Targeted retroareolar ultrasoundFirst step - Why
- Demonstrate dilated ducts, inflammatory change and a drainable periareolar collection.
- Interpretation and limitations
- Duct debris can mimic solid tissue, so Doppler, compression and targeted sampling help; a defined collection is assessed for image-guided aspiration or drainage.
- 02
Age-appropriate mammography - Why
- Evaluate persistent retraction, discharge or mass for calcification, distortion and occult malignancy.
- Interpretation and limitations
- Inflammation may increase density and limit interpretation. Repeat or additional imaging after acute symptoms settle is needed when underlying tissue remains unexplained.
- 03
Abscess aspiration and culture - Why
- Achieve source control and identify organisms that can refine antimicrobial treatment.
- Interpretation and limitations
- Send pus rather than a superficial swab where possible. A negative culture after prior antibiotics does not disprove abscess, so clinical and ultrasound response remain important.
- 04
Core or nipple-skin biopsy - Why
- Exclude malignancy when a solid target, persistent inflammation or suspicious surface change remains.
- Interpretation and limitations
- Image-guided core addresses a mass; a punch specimen addresses Paget-like skin. Benign inflammation must explain the complete clinical and imaging phenotype.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Intraductal papilloma
Papilloma more often causes spontaneous clear or bloody single-duct discharge and may appear as a vascular intraductal mass.
Inflammatory or central cancer
Carcinoma can cause retraction, discharge, mass and erythema; absent improvement or suspicious imaging requires representative tissue diagnosis.
Granulomatous mastitis
Idiopathic granulomatous mastitis is a sterile lobulocentric diagnosis reached after tissue and microbiological investigation. Infectious granulomatous disease exists, including Corynebacterium-associated cystic neutrophilic granulomatous mastitis, so unexplained masses, abscesses and sinuses require core and targeted cultures before immunosuppression.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Acute non-lactating abscess pathwayDrain the collection and prescribe a scoped adult regimenFirst stepA non-lactating adult who smokes has periareolar cellulitis and an ultrasound-confirmed abscess but is haemodynamically stable and suitable for outpatient care.+
- 1Assess observations, sepsis, spreading cellulitis, skin necrosis, diabetes, immune status, penicillin allergy and previous MRSA; systemic illness, necrosis or other high-risk features require same-day admission and the separate intravenous pathway.
- 2Arrange ultrasound-guided aspiration or drainage and send pus for culture and susceptibility. An organised collection needs source control, not antibiotics alone.
- 3Under the current NHS Highland adult local pathway, give oral flucloxacillin 500 mg four times daily; because this patient smokes, add oral metronidazole 400 mg three times daily. Use 7 to 10 days for abscess and 10 to 14 days for mastitis, then refine against culture and response.
- 4Review symptoms, cellulitis margins, adverse effects and residual cavity promptly. If systemically unwell, admit under the NHS Highland local specialist/formulary pathway: it lists intravenous flucloxacillin 1 to 2 g four times daily and, when anaerobic cover is indicated, metronidazole 500 mg three times daily. Breast infection lies outside the selected IV products’ listed indications, so this branch requires local authorisation and patient-specific prescribing. Give the selected flucloxacillin slowly after appropriate reconstitution or dilution; infuse Baxter metronidazole 500 mg/100 mL over 20 to 60 minutes and switch to oral treatment as soon as feasible.
02Recurrent fistula pathwayTreat the diseased duct after infection controlThree periareolar abscesses have occurred at the same site and a small opening intermittently drains at the areolar margin.+
- 1Map prior procedures and cultures, assess continuing smoking and use focused imaging to define any active collection, sinus and persistent breast abnormality.
- 2DefinitiveControl acute sepsis with drainage, culture-guided treatment and reassessment before definitive surgery; smoking cessation is encouraged and supported but is not a prerequisite for an operation.
- 3During a quiescent interval, discuss excision of the diseased central duct, sinus, scar and fistula tract with the specialist breast team, including wound breakdown, altered nipple sensation and recurrence.
- 4Confirm final pathology and wound closure, and provide rapid access for recurrence rather than treating temporary sinus closure as permanent resolution.
03Non-resolving inflammation pathwayReopen the diagnosis after treatment failureRetroareolar erythema and retraction persist after drainage and culture-directed antibiotics, with no remaining fluid cavity.+
- 1Confirm adherence, susceptibility and source control, then repeat examination for a solid mass, peau d’orange, ulceration or abnormal nodes.
- 2Repeat targeted ultrasound; the 2026 PDM-SMOLD consensus also recommends repeat ultrasound when initial antibiotic treatment has not produced improvement after 1 to 2 weeks.
- 3Core-biopsy persistent or atypical tissue to exclude malignancy. If granulomatous mastitis is considered, obtain tissue and appropriate aerobic, anaerobic, mycobacterial, fungal and Corynebacterium investigations before calling it idiopathic.
- 4Distinguish idiopathic sterile lobulocentric inflammation from infectious granulomatous disease, including cystic neutrophilic granulomatous mastitis associated with Corynebacterium, before immunosuppression or further antimicrobial treatment is chosen.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
Flucloxacillin
NHS Highland adult local regimen: 500 mg by mouth four times daily for 7 to 10 days for breast abscess or 10 to 14 days for non-lactating mastitis. If systemically unwell and admitted, its separate local branch lists 1 to 2 g intravenously four times daily; breast infection is outside the selected 2 g IV product's listed indications, so use requires the local specialist/formulary pathway.Do not use with penicillin or other beta-lactam hypersensitivity or previous flucloxacillin-associated jaundice or hepatic dysfunction. Take the oral capsule on an empty stomach with a full glass of water and do not lie down immediately. For the selected IV product, dissolve 2 g in 40 mL water for injections for slow intravenous injection, or administer suitably diluted over 20 to 30 minutes. If creatinine clearance is below 10 mL/min, reduce the dose or extend the interval and do not exceed 1 g every 8 to 12 hours. Monitor potassium with high doses, especially with other hypokalaemia risks, and review renal/hepatic function, sodium load and neurotoxicity risk.
Metronidazole
NHS Highland adult local add-on for a smoker or recurrent abscess: 400 mg by mouth three times daily for the same 7 to 10 day abscess course or 10 to 14 day mastitis course. Its separate systemic-illness branch lists 500 mg intravenously three times daily; oral use is preferred when possible. Breast infection is outside Baxter's selected IV product indications, so this example depends on the local specialist/formulary pathway.Avoid in nitroimidazole hypersensitivity and take oral tablets during or after food. For the oral product, avoid alcohol during treatment and for at least 48 hours afterwards. If oral treatment exceeds 10 days, arrange regular clinical and laboratory review, especially leucocyte count, and monitor for peripheral or central neurological toxicity. For Baxter IV metronidazole, infuse 500 mg/100 mL over 20 to 60 minutes, change to oral as soon as feasible, avoid alcohol through 72 hours after treatment, and use prolonged IV therapy only after strict benefit-risk review with specialist clinical and biological surveillance. Advanced hepatic insufficiency requires dose reduction and serum-level monitoring; also check warfarin or other coumarins, lithium, renal-metabolite toxicity and neurological symptoms.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Recurrent periareolar abscess
The obstructed pathological duct can seed repeated collections at the same areolar margin despite apparently successful short antibiotic courses.
Mammary duct fistula
A chronic skin-duct connection causes intermittent purulent drainage, pain and scarring and often needs specialist excision after acute infection settles.
Nipple distortion
Repeated inflammation and fibrosis can retract the nipple, creating cosmetic concern and diagnostic difficulty because malignancy can look similar.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- After aspiration, review fever, pain, erythema dimensions and residual cavity; repeat drainage may be needed when fluid reaccumulates.
- Check culture and susceptibility against the prescribed antibiotic and document route, stop date, allergy status and adverse effects. If oral metronidazole is needed beyond 10 days, perform regular clinical and laboratory monitoring, especially leucocyte count, and ask about paraesthesia, ataxia, dizziness or seizures; prolonged IV therapy requires specialist clinical and biological surveillance.
- Record smoking status and cessation support at each recurrent episode because continued exposure affects long-term surgical success.
- After duct or fistula excision, review wound healing, nipple viability and final histology, then define rapid access for new swelling.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Ectasia is not infection
Dilated ducts and coloured discharge can exist without bacterial disease. Antibiotics are reserved for clinical infection rather than prescribed for every ectatic image.
Fistula records previous rupture
A periareolar sinus often connects skin to a pathological subareolar duct after abscess drainage. Treating only the opening leaves the internal source.
Inflammation can conceal cancer
Oedema and pain make palpation and imaging harder. Persistent inversion or mass after infection settles deserves fresh assessment rather than attribution to scar.
Smoking discussion is treatment
Smoking is strongly associated with periductal mastitis. A non-judgemental cessation offer belongs in the disease plan, especially before elective duct surgery.
11Common pitfallsFrequent interpretation and management errors.
- 01
Calling all coloured nipple discharge infected leads to unnecessary antibiotics and neglects whether the pattern is multiduct, spontaneous or bloody.
- 02
Using repeated oral antibiotics for a fluctuant abscess delays drainage and produces temporary improvement without source control.
- 03
Incising a recurrent sinus without defining the diseased duct can create more scarring while leaving the fistula mechanism intact.
- 04
Assuming persistent nipple inversion is post-inflammatory without repeat triple assessment can delay diagnosis of an underlying carcinoma.