How should I order a contrast‑enhanced CT scan to capture the portal‑venous phase?

How to Order a CT for Portal-Venous Phase

Order a contrast-enhanced CT abdomen and pelvis with IV contrast, specifying portal venous phase acquisition at 60-70 seconds after contrast injection begins, using 100-120 mL of iodinated contrast (350 mgI/mL) injected at 3-5 mL/s. 1, 2

Standard Protocol Parameters

The portal venous phase is the workhorse phase for most abdominal imaging and requires specific timing to optimize venous structure enhancement and liver lesion detection:

Contrast Administration

• Volume: 100-120 mL of contrast medium with 350 mg iodine/mL 3
• Injection rate: 3-5 mL/s 3, 1
• Timing: Acquire images at 70 seconds after beginning contrast injection 1, 2
  • Alternative timing: 60 seconds is acceptable 3
  • Range: 50-70 seconds captures the transition between enteric and portal phases 4

Technical Specifications

• Slice thickness: 2-3 mm for optimal resolution 4
• Reconstruction: Use thin slices (1-1.5 mm) with multiplanar reconstruction capability 1
• Coverage: Abdomen and pelvis (chest can be added if evaluating for metastases)

When to Order Portal Venous Phase

Portal venous phase is the primary phase for:

• Solid organ injury evaluation (liver, spleen, kidneys) 1
• Liver metastasis detection - hypodense metastases are most conspicuous 2, 5
• Venous structure assessment (portal vein, mesenteric veins) 2
• General abdominal pathology screening 1

Common Pitfalls to Avoid

Do NOT order "CT with contrast" without specifying the phase - this generic order may result in suboptimal timing that misses the portal venous window.

Avoid oral contrast in most situations - it delays the exam and does not improve sensitivity for most pathology 1. Exception: Consider neutral oral contrast for small bowel evaluation 4, 6.

Do not rely on fixed 70-second delay for all patients - while this is standard, patients with circulatory disturbances may benefit from bolus tracking 7. However, in patients without circulatory issues, fixed delay at 70 seconds performs equivalently to bolus tracking 7.

Multiphasic Considerations

If you need both arterial and portal venous phases (e.g., for pancreatic masses, liver lesion characterization, or vascular assessment):

• Late arterial phase: 45-50 seconds after injection start 2
• Portal venous phase: 70 seconds after injection start 2

For liver lesion characterization specifically, dual-phase imaging (arterial + portal venous) is required, as the dynamic enhancement pattern guides diagnosis 8, 5.

Sample Order Language

"CT abdomen and pelvis with IV contrast, portal venous phase. Inject 120 mL iodinated contrast (350 mgI/mL) at 4 mL/s. Acquire at 70 seconds post-injection. Thin-slice reconstruction (≤3 mm). No oral contrast."

This standardized approach ensures consistent, diagnostic-quality portal venous phase imaging across different clinical scenarios 1, 2.