When should a computed tomography (CT) scan of the abdomen and pelvis with enhancement be performed?

CT Abdomen and Pelvis with Enhancement: Indications and Recommendations

Contrast-enhanced CT of the abdomen and pelvis should be performed for suspected acute pathology requiring detailed visualization of organ parenchyma, vascular structures, and inflammatory processes, while non-contrast CT is preferred for suspected urolithiasis or in patients with contraindications to contrast.

Primary Indications for Enhanced CT Abdomen/Pelvis

Acute Abdominal/Pelvic Conditions

• Suspected complicated infections: Pyelonephritis, tubo-ovarian abscess, diverticulitis 1
• Poorly localized abdominal/pelvic pain with broad differential diagnosis 1
• Equivocal or non-diagnostic ultrasound findings requiring further evaluation 1
• Suspected malignancy requiring assessment of enhancement patterns, invasion, or metastasis 1

Specific Clinical Scenarios

Gynecologic Conditions

• Vulvar cancer recurrence: Contrast-enhanced CT is usually appropriate for detecting lymph node metastases (sensitivity 60%, specificity 90%) 1
• Pelvic inflammatory disease: Contrast enhancement helps identify subtle findings before gross anatomical changes occur 1
• Ovarian masses: Contrast helps characterize solid components and vascularity 1

Urologic Conditions

• Acute pyelonephritis (complicated): Contrast-enhanced CT has superior detection rate (84.4%) compared to ultrasound (40%) 1, 2
• Renal abscess: Better detected with contrast enhancement (missed in 4.6% of cases with non-contrast CT) 1

When Non-Enhanced CT is Preferred

• Suspected urolithiasis: Non-contrast CT is the gold standard (sensitivity 97%) 1, 2
• Contraindications to IV contrast: Severe allergy or eGFR <30 mL/min/1.73m² 2
• Acute hemorrhage: Non-contrast CT can effectively detect and localize active bleeding 3

Optimal Technical Parameters

• Contrast type: Non-ionic iodinated contrast media 2
• Volume: 100-150 mL (standard adult dose) 2
• Timing: Portal venous phase (approximately 70 seconds post-injection) 2
• Flow rate: 3.0 mL/s provides optimal enhancement of both arterial and venous structures 4

Clinical Impact of Contrast Enhancement

• Administration of IV contrast significantly improves detection of urgent pathology compared to non-contrast CT (p=0.004) 5
• Repeat CT within 72 hours is often unnecessary if the initial CT was performed with IV contrast 5
• Adherence to ACR appropriateness criteria for IV contrast administration increases detection of urgent pathology (p=0.02) 5

Common Pitfalls and Considerations

• Contrast timing errors: Scanning too early results in suboptimal venous enhancement; excessive delay reduces vessel opacification 2
• Renal function assessment: Always check eGFR before administering contrast 2
• Contrast reaction history: Critical to avoid overlooking contraindications 2
• Oral contrast: Generally not required for routine venous phase imaging but may be considered when bowel delineation is specifically needed 2

In patients with suspected acute abdominal pathology, contrast-enhanced CT significantly improves diagnostic accuracy and may prevent unnecessary repeat imaging, making it the preferred approach when not contraindicated.