What is the differential diagnosis (Dx) and workup for a patient with recurrent abscesses?

Differential Diagnosis and Workup for Recurrent Abscesses

For patients with recurrent abscesses, immediately search for local anatomical causes (pilonidal cyst, hidradenitis suppurativa, foreign material) and drain/culture each recurrence early, while screening for diabetes mellitus and considering Crohn's disease, especially if perianal. 1

Differential Diagnosis

Local/Anatomical Causes (Most Common)

• Pilonidal cyst - particularly in sacrococcygeal region 1
• Hidradenitis suppurativa - chronic inflammatory condition of apocrine glands 1
• Retained foreign material - from prior trauma or procedures 1
• Anal fistula - associated with approximately one-third of anorectal abscesses 1

Underlying Systemic Conditions

• Crohn's disease - develops anorectal abscess in approximately one-third of patients; must be excluded in all recurrent cases, especially perianal 1
• Diabetes mellitus - undetected diabetes is a key predisposing factor 1
• Staphylococcus aureus colonization - including MRSA, which can cause recurrent skin infections 1
• Neutrophil dysfunction disorders - only if recurrent abscesses began in early childhood 1
• Immunodeficiency states - acquired or innate 2

Infectious Causes

• Community-acquired MRSA - now accounts for substantial proportion of skin abscesses 3
• Tuberculosis - in endemic areas or with appropriate exposure history 1

Initial Workup

History and Physical Examination

• Detailed medical history focusing on: 1

  • Age of onset (childhood onset suggests neutrophil disorders) 1
  • Pattern and location of recurrences
  • History of inflammatory bowel disease symptoms
  • Trauma or injection drug use 1
  • Previous surgical procedures

• Complete physical examination including: 1

  • Careful perineal inspection for surgical scars, anorectal deformities
  • Signs of perianal Crohn's disease
  • External fistula openings
  • Digital rectal examination (may require sedation/anesthesia due to pain) 1
  • Interdigital toe spaces examination for lower extremity cases 1

Laboratory Testing

Essential Initial Labs:

• Serum glucose and hemoglobin A1c - to identify undetected diabetes mellitus 1
• Urine ketones - for diabetes screening 1
• Complete blood count - assess for leukocytosis/leukopenia 1, 4

Additional Labs if Systemic Signs Present (fever, tachycardia, SIRS):

• Serum creatinine 1
• Inflammatory markers (C-reactive protein, procalcitonin, lactate) 1
• Blood cultures - if bacteremic or systemically ill 1

Microbiological Studies

• Culture and sensitivity of abscess drainage - mandatory for all recurrent abscesses 1
• Obtain early in course of infection 1
• Helps guide antibiotic therapy for 5-10 day course 1

Imaging Studies

• Not routinely required for superficial abscesses 1
• CT scan indicated for: 1
  • Suspected deep abscesses (intersphincteric, supralevator, ischiorectal)
  • Unclear diagnosis
  • Evaluation for underlying Crohn's disease complications
  • Assessment of extent before surgical planning

Management Algorithm

Immediate Management

1. Incision and drainage - primary treatment for all recurrent abscesses 1
2. Culture the drainage - send for aerobic/anaerobic cultures 1
3. Antibiotic therapy (5-10 days) based on culture results 1
   • If MRSA suspected/confirmed: vancomycin or linezolid 4
   • Cover MRSA if: penetrating trauma, known MRSA colonization, injection drug use, or SIRS present 1

Decolonization Protocol for Recurrent S. aureus

Consider 5-day decolonization regimen: 1

• Intranasal mupirocin twice daily
• Daily chlorhexidine washes (or dilute bleach baths: 1/4-1/2 cup per full bath) 1
• Daily decontamination of personal items (towels, sheets, clothes) 1
• Note: Efficacy data for MRSA era is limited, but may reduce recurrences 1

Specialized Evaluation

• Evaluate for neutrophil disorders only if recurrent abscesses began in early childhood 1
• Gastroenterology referral if Crohn's disease suspected (perianal location, systemic symptoms, family history) 1
• HIV testing should be considered in non-traumatic cases 1

Critical Pitfalls to Avoid

• Do not miss local anatomical causes - these require definitive surgical correction, not just drainage 1
• Do not delay drainage - antibiotics alone are insufficient without source control 1, 4
• Do not assume adult-onset recurrent abscesses indicate immunodeficiency - neutrophil function testing only needed if childhood onset 1
• Do not overlook Crohn's disease - must be actively excluded in all recurrent anorectal abscesses 1
• Do not forget diabetes screening - undetected diabetes is a major reversible risk factor 1
• Do not rely on decolonization alone - address underlying anatomical or systemic causes first 1