Should intravenous contrast be used for a computed tomography of the chest, abdomen, and pelvis to locate a source of infection?

CT Chest/Abdomen/Pelvis for Infection Source: Use IV Contrast

Yes, intravenous contrast should be used for CT chest/abdomen/pelvis when searching for an infection source, as it provides superior diagnostic yield and directly impacts patient management. 1

Evidence Supporting IV Contrast Use

Diagnostic Performance

• CT with IV contrast detects infection sources in 76.5% of septic patients, with a positive predictive value of 81.82% (CI: 76.31%-86.28%) 1
• The high detection rate leads to management changes in 45% of patients, including alterations in antimicrobial therapy, surgical intervention, and drainage procedures 1
• Most common infection sources identified are chest (38.6%), abdomen (22%), and pelvis/genitourinary tract (20.5%) 1

Expert Consensus Position

• The American College of Radiology states that CT without IV contrast is "less likely to detect a source of infection" and "not appropriate as first-line examination" in patients with non-localized symptoms 1
• While one study found no significant difference in radiologist confidence between contrast and non-contrast scans (P=0.432), this does not translate to equivalent diagnostic accuracy in clinical practice 1

When Non-Contrast CT May Be Considered

Specific Clinical Scenarios

• Suspected urosepsis from obstructing renal or ureteral calculi - non-contrast CT is appropriate here as stones are better visualized without contrast 1
• Acute renal failure - patients with sepsis frequently develop renal impairment, making contrast administration risky 1

Important Caveat

Even in renal failure cases, the ACR acknowledges this creates a clinical dilemma, as non-contrast studies have significantly reduced sensitivity for detecting infection sources 1

Practical Algorithm

1. First-line approach: CT chest/abdomen/pelvis WITH IV contrast for undifferentiated sepsis 1, 2

2. Check contraindications:

   • Severe renal impairment (consider risk vs. benefit)
   • Contrast allergy (consider premedication or alternative imaging)
   • Recent contrast administration within 3 days 3

3. If contrast contraindicated:

   • Proceed with non-contrast CT only if clinical urgency demands immediate imaging 1
   • Recognize the significantly reduced diagnostic sensitivity 1
   • Consider alternative imaging (ultrasound for specific targets, MRI if patient stable enough) 1

4. Special consideration for suspected urolithiasis: Use non-contrast CT as first-line 1

Why Not Both (With and Without Contrast)?

There is no data supporting added value of obtaining both non-contrast and contrast-enhanced CT for sepsis evaluation 1. This approach:

• Doubles radiation exposure without improving diagnostic accuracy
• Delays time to diagnosis
• Increases cost without clinical benefit 1

Common Pitfalls to Avoid

• Ordering non-contrast CT "to be safe" in borderline renal function - this often results in non-diagnostic studies requiring repeat imaging with contrast, exposing patients to additional radiation and delays in diagnosis 4
• Assuming oral contrast is necessary - IV contrast alone is sufficient and preferred, as oral contrast delays imaging and provides minimal additional benefit for infection source localization 1, 5
• Ordering limited anatomic coverage - when infection source is unclear, chest/abdomen/pelvis coverage is superior to single-region imaging, as 81% of infection sources are distributed across these three regions 1