Abscess - General
🟡 A skin abscess is a localized collection of pus within the dermis or deeper skin tissues, usually caused by bacterial infection. ✂️ For a fluctuant abscess, the main treatment is usually incision and drainage — antibiotics alone are often insufficient. The key pathophysiology is that an abscess is not just “infection” but a walled-off pus collection. Once a cavity has formed, antibiotic penetration is poor, which is why source control by drainage is so important.
ℹ️ About
- 🔥 A skin abscess is a painful, tender, swollen collection of pus, usually surrounded by erythema and inflammation.
- 🦠 It is most commonly caused by bacterial infection, especially Staphylococcus aureus.
- ⚠️ This page refers mainly to cutaneous abscesses / boils / carbuncles. Deep abscesses (for example psoas or intra-abdominal) and special-site abscesses (for example perianal or breast) need site-specific assessment.
🧬 Risk Factors / Aetiology
- Diabetes 🍬: Increased susceptibility to skin and soft tissue infection.
- Immunocompromise 🛡️: Higher risk of severe, recurrent, or atypical infection.
- Skin trauma / shaving / friction ✂️: Can predispose to follicular infection.
- Staphylococcal carriage 🦠: Associated with recurrent boils and carbuncles.
- IV drug use (IVDU) 💉: Raises concern for groin abscess, deeper infection, and pseudoaneurysm — imaging may be needed before drainage.
🩺 Clinical Features
- 🔴 Localized, painful, erythematous swelling.
- 🟡 Fluctuance may suggest a drainable pus collection.
- 🤕 Tenderness, warmth, and surrounding cellulitis may be present.
- 🌡️ Fever or systemic upset suggests more significant infection.
- ⚠️ Red flags include rapidly spreading infection, facial abscess, sepsis, immunocompromise, or failure to improve.
🧾 Types / Special Sites
- 🧴 Skin abscess
- 🌋 Boil (furuncle)
- 🧩 Carbuncle
- 🍑 Pilonidal abscess
- 🚽 Perianal abscess
- 💉 Groin abscess in IVDU — consider pseudoaneurysm first
- 🦵 Psoas / deep abscess — usually needs imaging and specialty input
🔬 Investigations
- Clinical assessment 👀: Many uncomplicated superficial abscesses are diagnosed clinically.
- Blood tests 🧪: Consider FBC, CRP, U&E, glucose/HbA1c if systemically unwell, recurrent infection, or significant comorbidity.
- Pus culture 🧫: Consider if recurrent, severe, unusual, healthcare-associated, immunocompromised, or not responding to treatment.
- Blood cultures 🩸: Only if there are signs of sepsis or suspected bacteraemia.
- Ultrasound 📷: Useful if the diagnosis is uncertain, to confirm a fluid collection, or before drainage of a suspected groin abscess in IVDU.
- CT / deeper imaging 🖥️: Reserved for suspected deep abscesses such as psoas or intra-abdominal infection.
- HIV testing 🧍: Consider in selected high-risk patients or recurrent/unusual infection, not as a universal test for simple abscesses.
🦠 Microbiology
- Common organisms: Staphylococcus aureus is the most common cause of skin abscesses.
- Other organisms: Streptococcus pyogenes, anaerobes, enteric Gram-negatives, or mixed flora may occur depending on site.
- MRSA ⚡: Consider based on local prevalence, previous microbiology, recurrent infection, or healthcare exposure.
🛠️ Management
- Incision and drainage ✂️: Main treatment for a fluctuant skin abscess.
- Antibiotics 💊: Usually reserved for surrounding cellulitis, systemic infection, facial abscess, immunocompromise, significant comorbidity (including poorly controlled diabetes), or failure of local management.
- Analgesia 💊: Provide adequate pain relief.
- Wound care 🩹: Dressings and follow-up may be needed after drainage.
- Diabetes optimisation 🍬: Improve glycaemic control to support recovery.
- Specialist referral 👨⚕️:
- Facial abscess 😬: Lower threshold for urgent specialist review.
- Breast abscess 👩🍼: Breast team / appropriate specialty input.
- Perianal abscess 🚽: Surgical review.
- IVDU groin abscess 💉: Ultrasound first to exclude pseudoaneurysm before drainage.
- Deep abscesses 🦵: Imaging + specialty review.
🚨 When to Escalate / Refer Urgently
- 🌡️ Signs of sepsis or systemic illness.
- 🔴 Rapidly spreading cellulitis.
- 😵 Immunocompromised patient or poorly controlled diabetes.
- 😬 Abscess on the face or near important structures.
- 📈 Large, very painful, or recurrent abscess.
- ❌ Failure to improve with primary care management.
📚 References
