Does a patient with suspected cellulitis and history of intravenous (IV) drug abuse require a computed tomography (CT) scan with or without contrast?

From the Guidelines

Initial Evaluation

For patients with a history of intravenous drug abuse suspected of having cellulitis, a non-contrast computed tomography (CT) scan is typically sufficient for initial evaluation 1.

Use of Contrast

The use of contrast is not routinely recommended unless there is suspicion of abscess or necrotizing fasciitis, in which case a contrast-enhanced CT scan with 100-150 mL of iodinated contrast (e.g., iohexol or ioversol) administered intravenously at a rate of 2-3 mL/s may be considered 1.

Clinical Diagnosis and Management

However, in most cases of uncomplicated cellulitis, clinical diagnosis and management with antibiotics such as cefazolin 1-2 grams every 8 hours or ceftriaxone 1-2 grams every 24 hours for 7-10 days is adequate, and imaging with CT is not necessary 1.

Key Points

• Non-contrast CT scan is usually sufficient for initial evaluation of cellulitis in patients with a history of IV drug abuse.
• Contrast-enhanced CT scan may be considered if there is suspicion of abscess or necrotizing fasciitis.
• Clinical diagnosis and management with antibiotics is often adequate for uncomplicated cellulitis, and imaging with CT may not be necessary.
• The choice of imaging modality and use of contrast should be guided by the clinical presentation and suspicion of complications 1.

From the FDA Drug Label

Because unenhanced scanning may provide adequate diagnostic information in the individual patient, the decision to employ contrast enhancement, which may be associated with risk and increased radiation exposure, should be based upon a careful evaluation of clinical, other radiological, and unenhanced CT findings.

The decision to use a CT scan with or without contrast for a patient with suspected cellulitis and a history of intravenous (IV) drug abuse should be based on a careful evaluation of clinical, radiological, and unenhanced CT findings. Contrast enhancement may be useful, but it is not directly indicated by the provided drug labels. The labels provide guidance on the use of contrast agents, such as iohexol and ioversol, but do not specifically address the diagnosis of cellulitis or the consideration of a patient's history of IV drug abuse in the decision to use contrast.

• Key considerations include the potential benefits of contrast enhancement in diagnosing cellulitis, such as improved visualization of soft tissue infections, and the potential risks, such as allergic reactions or nephrotoxicity.
• Clinical judgment is necessary to weigh these factors and make a decision about the use of contrast in this patient population 2.

From the Research

Patient Evaluation

• A patient with suspected cellulitis and a history of intravenous (IV) drug abuse may require imaging to evaluate the extent of infection and potential complications.
• The use of computed tomography (CT) scans with or without contrast can be beneficial in evaluating soft tissue infections, including cellulitis, as it provides excellent anatomic resolution and soft tissue contrast 3.

CT Scan with Contrast

• A CT scan with contrast can help identify complications such as abscesses or intracranial extension of infection, which is critical in patients with suspected orbital cellulitis 4.
• The use of IV contrast-enhanced CT scans has been shown to have high sensitivity and specificity in identifying necrotizing soft tissue infections (NSTIs), which can be a complication of cellulitis 5.

CT Scan without Contrast

• Non-contrast CT scans can be useful in evaluating vascular structures and identifying clues to vascular disorders, which can be important in patients with a history of IV drug abuse 6.
• However, non-contrast CT scans may not provide sufficient information to evaluate the extent of soft tissue infection, and contrast may be necessary to accurately diagnose and manage cellulitis.

Safety of Contrast Media

• The use of non-ionic iodinated contrast media (NICM) in CT examinations is generally safe, with a low incidence of adverse drug reactions (ADRs) 7.
• However, certain factors such as the type of contrast medium and the season may be associated with a higher risk of acute ADRs, and patients should be carefully evaluated and monitored when receiving contrast media.