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Referral and warning signs
When to refer
Refer to hospital (HC4/H/RR) for: Suspected pyomyositis requiring IV antibiotics. Confirmed or suspected abscess requiring surgical drainage.
Red flags
- Fluctuant muscle swelling
- High fever, signs of sepsis
- Severe, unrelenting pain
- Rapid progression of swelling/erythema
- Signs of compartment syndrome
Signs and symptoms
- Often localized to a single muscle group.
- Fever, chills, malaise.
- Painful swelling of the involved muscle.
- Affected area is often warm, tender, and indurated (firm/woody feel initially).
- Limited movement of the adjacent joint due to pain/swelling.
- Fluctuance develops later as pus collects (abscess stage).
- Skin overlying may be initially normal, later becomes erythematous and warm.
Risk factors
- Residence in or travel to tropical/subtropical regions.
- Immunodeficiency (HIV infection common association).
- Trauma or strenuous muscle exertion (may predispose).
- Malnutrition.
- Diabetes Mellitus.
Diagnosis
Clinical assessment
Suspect based on fever and localized painful muscle swelling, especially in endemic area or immunocompromised host. Differentiate from cellulitis, osteomyelitis, septic arthritis, DVT, haematoma.
Investigations
- Blood tests: CBC (leucocytosis, often eosinophilia initially), ESR/CRP (elevated), Blood cultures (may be positive).
- Imaging: Ultrasound (identifies fluid collections/abscesses, guides aspiration), CT Scan / MRI Scan (detailed visualization).
- Aspiration of fluctuant area: Gram stain and Culture & Sensitivity of pus (Staphylococcus aureus most common).
- HIV testing (strongly consider).
Diagnostic criteria
Clinical suspicion supported by imaging showing intramuscular fluid collection/abscess +/- positive blood culture or aspirate culture.
Management
Non-pharmacological management
- Rest and elevation.
- Immobilisation (splinting) for comfort.
- Surgical Drainage: Essential once abscess confirmed. Incision and drainage.
- Warm compresses (early stage).
Pharmacological treatment
- Antibiotics: Required. Cover Staphylococcus aureus.
- - Cloxacillin IV/PO 500mg-1g Q6H (Child: 12.5-25mg/kg/dose Q6H) for 5-10 days (or longer).
- - Vancomycin if MRSA suspected.
- - Tailor based on culture/sensitivity if available.
- Analgesia (Paracetamol, NSAIDs, Opioids).
Monitoring
Monitor clinical response (fever, pain, swelling). Monitor wound healing. Monitor inflammatory markers.
Complications
- Sepsis
- Metastatic infection
- Muscle necrosis / fibrosis / contracture
- Compartment syndrome (rare)
- Rhabdomyolysis (rare)
Prevention
- Good hygiene.
- Prompt treatment of skin infections.
- Management of underlying immunosuppression (ART for HIV).
Patient education
- Explain pyomyositis as a muscle infection/abscess.
- Need for antibiotics and possibly surgical drainage.
- Importance of completing antibiotic course.
- Wound care instructions.
- Need for rest and follow-up.
Uganda-specific notes
More common than in temperate climates, strongly associated with HIV infection. Staphylococcus aureus usual pathogen. Early diagnosis and treatment (antibiotics +/- drainage) crucial. Ultrasound useful if available.
References
- Uganda Clinical Guidelines (UCG) 2023
Chapter 10, Section 10.1.3