Treatment of Intramuscular Abscess
The treatment of intramuscular abscess requires early surgical drainage combined with empiric intravenous vancomycin, followed by culture-directed antibiotic therapy for 2-3 weeks. 1
Immediate Management
Diagnostic Imaging
- MRI is the gold standard imaging modality for establishing the diagnosis of intramuscular abscess (pyomyositis), though CT scan and ultrasound are also useful alternatives 1
- Repeat imaging should be performed in patients with persistent bacteremia to identify undrained foci of infection 1
Microbiological Workup
- Obtain cultures of both blood and abscess material before initiating antibiotics whenever possible 1
- This is critical for tailoring antibiotic therapy and identifying resistant organisms 1
Surgical Intervention
Early drainage of purulent material must be performed and is the cornerstone of treatment 1. The specific surgical approach depends on abscess location:
- For subscapular abscesses, tendon-sparing approaches (posterior inferomedial, deltoid-pectoral, or dorsal subscapularis approach) can access most locations within the subscapular space 2, 3
- Surgical irrigation with debridement is essential for eradication of infection and removal of any retained foreign material 4
Antibiotic Therapy
Empiric Treatment
Vancomycin is recommended for initial empirical therapy to cover methicillin-resistant Staphylococcus aureus (MRSA), the most common pathogen 1
Additional coverage considerations:
- Add an agent active against enteric gram-negative bacilli (such as a third-generation cephalosporin or fluoroquinolone) for immunocompromised patients or following open trauma to muscles 1
- For polymicrobial infections with purulent drainage, consider adding coverage for anaerobes 5, 4
Culture-Directed Therapy
Once microbiology results are available:
- For methicillin-sensitive S. aureus (MSSA), switch to cefazolin or antistaphylococcal penicillin (nafcillin or oxacillin) 1
- Adjust antibiotic spectrum based on culture and sensitivity results 1
Duration and Route
- Antibiotics should be administered intravenously initially 1
- Once the patient is clinically improved, oral antibiotics are appropriate for patients whose bacteremia cleared promptly and those with no evidence of endocarditis or metastatic abscess 1
- Total duration of therapy is 2-3 weeks 1
Special Populations
Diabetic Patients
- Diabetic patients are at higher risk for intramuscular abscess formation and may present with septic shock 6
- These patients require aggressive early intervention with both surgical drainage and broad-spectrum antibiotics 6, 4
- Consider polymicrobial infection including oral flora and anaerobes if there is a history of penetrating injury 4
Immunocompromised Patients
- Broader empiric coverage is essential, including gram-negative organisms 1
- Consider extended antibiotic courses and more aggressive surgical debridement 7
Critical Pitfalls to Avoid
- Do not delay surgical drainage - antibiotics alone are insufficient for intramuscular abscesses 1, 2
- Do not miss concomitant infections - intramuscular abscesses can lead to bacteremia, septic arthritis, osteomyelitis, or even bacterial meningitis via hematogenous spread 3
- Do not assume single-organism infection - penetrating injuries can introduce polymicrobial flora including anaerobes from skin, oral cavity, or gastrointestinal tract 4
- Do not discontinue antibiotics prematurely - persistent bacteremia or undrained collections require repeat imaging and possible repeat surgical intervention 1