Should a CT scan with or without contrast be used to evaluate osteomyelitis?

CT for Evaluation of Osteomyelitis: With or Without Contrast

For evaluation of osteomyelitis, CT with contrast is recommended when CT is the chosen modality, as contrast helps assess soft tissue involvement and identify abscess formation, though CT is generally insensitive for acute osteomyelitis detection.

Role of CT in Osteomyelitis Diagnosis

• CT is generally insensitive in the evaluation of acute osteomyelitis and should not be the primary imaging modality when osteomyelitis is suspected 1
• CT is most useful for characterizing osseous changes in chronic osteomyelitis, particularly for detecting sequestrum (dead bone fragments) 1
• While CT provides excellent bone detail, MRI is the preferred imaging modality for osteomyelitis due to its superior sensitivity and specificity 1

CT With Contrast vs. Without Contrast

• When CT is used, intravenous contrast administration is recommended as it helps assess soft tissue involvement and identify abscess formation 1
• Although IV contrast does not improve diagnostic sensitivity for acute osteomyelitis itself, it significantly improves evaluation of associated soft tissue infections 1
• There is no added benefit to performing multiphase CT imaging (before and after contrast) in the evaluation of infection 1

Limitations of CT for Osteomyelitis

• CT has lower sensitivity compared to MRI for detecting early bone marrow changes in acute osteomyelitis 1
• CT may be affected by metal artifacts when evaluating osteomyelitis near orthopedic hardware 1
• Radiation exposure is a consideration, especially in pediatric patients 1

Superior Alternatives to CT

• MRI is highly accurate for detection of acute osteomyelitis with high sensitivity (82%-100%) and specificity (75%-96%) 1
• MRI provides excellent evaluation of marrow signal changes and adjacent soft tissues including abscesses and fistulas 1
• For patients who cannot undergo MRI, nuclear medicine studies such as 3-phase bone scan (sensitivity 83%) or FDG-PET/CT (sensitivity 81%-100%, specificity 87%-100%) may be considered 1

Special Considerations

• In chronic osteomyelitis, CT with contrast may be more valuable for detecting sequestrum and cortical destruction 1
• For suspected osteomyelitis with implanted hardware, CT with contrast can help evaluate hardware complications and developing osteolysis 1
• In pediatric patients, MRI is strongly preferred over CT due to radiation concerns and superior diagnostic performance 1

Clinical Algorithm for Imaging Selection

1. Start with plain radiographs for initial evaluation 1
2. If osteomyelitis is still suspected:
   • Choose MRI as the preferred next imaging modality 1
   • Consider CT with contrast only if:
     • MRI is contraindicated
     • Evaluation of chronic changes or sequestrum is needed
     • Assessment of hardware complications is required 1
3. If CT is performed, always use contrast unless contraindicated 1