In a patient with a left‑sided acute ischemic stroke, an initial normal non‑contrast head CT, and compensated Child‑Pugh A cirrhosis, can a repeat non‑contrast CT performed 24–48 hours after symptom onset reliably detect the infarct, or is contrast‑enhanced CT required?

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Repeat CT at 24 Hours Can Detect Left-Sided Ischemic Infarct: Use Non-Contrast CT

A repeat non-contrast CT performed 24–48 hours after symptom onset will reliably detect a left-sided ischemic infarct that was missed on the initial CT, and contrast-enhanced CT offers no additional benefit for this purpose. 1

Evidence Supporting Repeat Non-Contrast CT

Detection Rate at 24 Hours

  • Approximately 25% of acute ischemic stroke patients with a normal initial CT will demonstrate acute or subacute infarction on follow-up imaging performed within 1–2 days, confirming the diagnosis and facilitating secondary prevention counseling 2
  • This 25% diagnostic yield applies to all stroke locations, including anterior-circulation (left-sided) strokes, not just posterior circulation events 2
  • The American College of Cardiology specifically recommends that a repeat CT or MRI brain scan should be performed at 24 hours after initial stroke event, regardless of clinical stability 2

Why Non-Contrast CT Is Sufficient

  • There is no relevant literature to support the use of contrast-enhanced CT of the head in the evaluation of ischemic stroke 1
  • The American College of Radiology explicitly states that there is no role for IV contrast in CT evaluation of evolving or subacute infarct, as contrast enhancement within previously undocumented subacute infarcts can cause confusion with other brain lesions 2
  • Non-contrast CT is preferred for follow-up due to its quick repeatability and ease of comparison to prior examinations 2

Clinical Algorithm for Your Patient

At 24–48 Hours Post-Symptom Onset:

  1. Order a repeat non-contrast head CT (not contrast-enhanced) 2

  2. The scan will likely demonstrate:

    • Hypodensity in the affected territory (left MCA distribution if that's the clinical localization)
    • Loss of gray-white differentiation
    • Sulcal effacement
    • Possible hyperdense vessel sign if still present 3

  3. Use specialized "stroke windows" settings when reviewing the CT, as this significantly improves detection of early ischemic changes (70% detection vs. 18% with standard windows) 3

Special Consideration for Cirrhosis

  • In your patient with compensated Child-Pugh A cirrhosis, non-contrast CT is actually preferable to contrast-enhanced CT because:
    • It avoids unnecessary contrast exposure in a patient with liver disease
    • Contrast offers no diagnostic advantage for detecting established infarct 1
    • The 24-hour timepoint allows sufficient evolution of cytotoxic edema to be visible on non-contrast CT 2

Why MRI Would Be Superior (But CT Is Adequate)

While the question asks specifically about CT, it's worth noting that:

  • MRI with diffusion-weighted imaging detects approximately 32.5% of acute infarcts missed on initial CT, with particular benefit for posterior circulation strokes 2
  • However, diffusion-weighted MRI can be falsely negative in roughly 50% of small posterior-fossa strokes within the first 48 hours, though this false-negative rate is considerably lower for anterior-circulation (left-sided) strokes 2
  • If the 24-hour non-contrast CT remains negative despite strong clinical suspicion, consider MRI with DWI as the next step 2

Common Pitfalls to Avoid

  • Do not order contrast-enhanced CT for stroke follow-up—it provides no benefit and may cause confusion 1, 2
  • Do not skip the 24-hour imaging even if the patient is clinically stable, as confirmation of infarct directly impacts secondary prevention strategies (antiplatelet selection, statin intensity, blood pressure goals) 2
  • Ensure the radiologist uses stroke-specific window settings (width 8, level 32) when interpreting the scan, as standard brain windows miss many early ischemic changes 3
  • Do not assume a negative 24-hour CT rules out stroke—if clinical suspicion remains high, proceed to MRI with DWI 2

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

2
Guideline

Timing of Follow-up Imaging After Ischemic Stroke

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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