Doctors Revision

Musculoskeletal System & Rheumatology

Pyomyositis

Bacterial infection primarily within skeletal muscle, often leading to abscess formation. Typically affects large muscle groups (e.g., thigh, buttock, calf). More common in tropical regions.

Also known as: Tropical Pyomyositis, Muscle Abscess

Open in the interactive guide
On this page

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

Scroll to Top