What is the treatment for an infected cyst?

Treatment for Infected Cysts

The primary treatment for an infected cyst is incision and drainage, which is strongly recommended as the cornerstone of management for inflamed epidermoid cysts, carbuncles, abscesses, and large furuncles. 1, 2

Diagnostic Approach

• Infected cysts typically present with inflammation, tenderness, erythema, and may have purulent drainage 2
• Gram stain and culture of pus from inflamed epidermoid cysts are not recommended as routine practice 1, 2
• Clinical features suggesting infection include fever, tenderness in the affected area, elevated inflammatory markers, and leukocytosis 3

Treatment Algorithm

Step 1: Incision and Drainage

• Incision and drainage is the definitive treatment for inflamed and infected cysts 1, 2
• After drainage, the wound should be covered with a dry dressing rather than packed with gauze, as packing may increase pain without improving healing outcomes 2
• The procedure involves making an incision over the fluctuant area of the cyst, evacuating the contents, and breaking up any loculations 1

Step 2: Antibiotic Therapy Considerations

• Systemic antibiotics are usually unnecessary for simple inflamed cysts after adequate drainage unless there are signs of systemic infection 2

• Indications for antibiotics include:

  • Temperature >38°C or <36°C
  • Tachypnea >24 breaths per minute
  • Tachycardia >90 beats per minute
  • White blood cell count >12,000 or <400 cells/µL
  • Extensive surrounding cellulitis
  • Immunocompromised state 2

• When antibiotics are deemed necessary, they should target Staphylococcus aureus, which is a common pathogen 2

• Recommended antibiotic options include:

  • Cephalexin 500 mg orally four times daily for 7-10 days 4
  • Clindamycin 300-450 mg orally four times daily for 7-10 days (especially if MRSA is suspected) 5
  • Trimethoprim-sulfamethoxazole (if MRSA is suspected) 1
  • Doxycycline (if MRSA is suspected) 1

Step 3: Special Considerations for Complex or Recurrent Cysts

• For large infected cysts (>5 cm), percutaneous catheter drainage combined with antibiotics may be more effective than antibiotics alone 3, 6
• For recurrent infections at the same site, complete excision of the cyst and its wall should be considered once the acute inflammation has resolved 2
• Surgical drainage may be necessary for multiloculated or complex cysts with high viscosity contents 3

Common Pitfalls to Avoid

• Avoid closing the wound without adequate drainage, as this may lead to recurrent infection 2
• Do not routinely prescribe antibiotics unless there are signs of systemic infection or the patient has markedly impaired host defenses 2
• Avoid packing the wound unnecessarily as it may increase pain without improving healing outcomes 2
• For infected cysts in patients with polycystic conditions, use caution with drainage as infection may spread to adjacent cysts 3, 6

Follow-up Care

• Continue antibiotic therapy based on culture results if cultures were obtained 3
• Follow-up imaging should be considered for complex cases to confirm resolution of the collection 3
• If recurrent infections occur, search for local causes such as foreign material 2