Synopsis
Diagnose a breast abscess with ultrasound, achieve minimally invasive source control where feasible, use microbiology to refine antibiotics, and recognise when admission, surgery or alternative diagnosis is required.
- A breast abscess is a localised collection of infected fluid, usually presenting with focal pain, swelling, erythema and fever after lactational or non-lactational mastitis.
- Ultrasound confirms fluid, measures depth and loculation, distinguishes phlegmon from drainable pus and guides aspiration away from vulnerable skin and implants.
- Needle aspiration is commonly used for accessible collections and may need repetition; catheter or operative drainage is selected for large, multiloculated, recurrent or poorly accessible abscesses.
Key red flags
Crepitus, skin necrosis, pain beyond the visible inflammation or rapid systemic decline requires emergency assessment for necrotising soft-tissue infection.
Investigation priorities
Confirm, map and measure drainable fluid and identify loculation or solid tissue.
Management branches
Ultrasound shows a unilocular 3 cm peripheral collection in a stable breastfeeding adult with a healthy term infant, preserved renal function, no relevant beta-lactam allergy and no known MRSA risk.
- Assess sepsis risk, allergy and feeding, then explain aspiration, possible repetition, bleeding, pain and the small risk of milk fistula.
- Before puncture, use aseptic preparation and local infiltration anaesthesia after checking the agent, dose ceiling, allergies and patient risks. Confirm adequate anaesthesia, then aspirate under ultrasound, send pus for culture and record the immediate reduction and residual volume.
Key medicines
Plain lidocaine 1% for local infiltrationAguettant lidocaine 10 mg/mL pre-filled syringe is a checked plain product for local intradermal/subcutaneous infiltration before drainage. Select the smallest effective dose for the procedure. Its usual adult infiltration total is 3–5 mg/kg, with a generally recommended maximum of 200 mg (20 mL of 1%); the ceiling is not a target dose. Use a lower patient-specific dose when indicated.Exclude allergy to lidocaine, amide local anaesthetics or excipients. Cardiac or hepatic insufficiency may require reduction by up to half; renal impairment, frailty, conduction disease, epilepsy and anticoagulation require individual review. Count other local anaesthetics and check antiarrhythmics and clearance-reducing interactions. Avoid intravascular injection; infected tissue can reduce effect while increasing absorption. Have resuscitation facilities available. Stop injection and summon help for perioral numbness, tinnitus, neurological change, seizure or cardiovascular disturbance; manage suspected local-anaesthetic systemic toxicity promptly. This is not an IVRA or adrenaline-mixture regimen. Recommended local doses permit continued breastfeeding.
Flucloxacillin after lactational abscess drainageFor the specified stable adult without relevant allergy or resistant-organism risk, NHS Highland recommends 500 mg orally four times daily for 7–10 days for breast abscess. The selected capsules are taken one hour before or two hours after food with a full glass of water (250 mL), without lying down immediately afterwards.Avoid beta-lactam/product hypersensitivity and previous flucloxacillin-associated hepatic injury. Assess liver disease; CrCl below 10 mL/min needs an individual lower-dose/longer-interval decision. Check warfarin/INR, methotrexate, probenecid and voriconazole interactions. If paracetamol is also used, severe renal impairment, sepsis or malnutrition warrants review for high anion gap acidosis risk and appropriate monitoring. Observe a healthy term infant for diarrhoea, thrush, rash or poor feeding. This example is not a prescription for MRSA, penicillin allergy, severe illness or recurrent smoking-related central disease.