Contraindications to CT Aortogram
The primary contraindications to CT aortography are severe iodinated contrast allergy and significant renal dysfunction, though neither represents an absolute contraindication when the study is clinically necessary and appropriate precautions are implemented.
Relative Contraindications Requiring Risk Stratification
Impaired Renal Function
- Significant renal dysfunction is the principal contraindication to CT aortography due to risk of contrast-induced nephropathy (CIN) 1.
- Patients with GFR <30 mL/min/1.73m² should avoid contrast-enhanced CT when possible 2.
- For patients with GFR 30-60 mL/min/1.73m², CT aortography can be performed with risk mitigation strategies including pre-procedural hydration with isotonic saline, use of low-osmolar or iso-osmolar contrast agents, and minimizing contrast volume 3, 2.
- Patients with normal renal function (GFR >60 mL/min) are at exceptionally low risk for CIN and can safely receive contrast 4, 3, 5.
- Recent evidence demonstrates that ultra-low contrast volumes (as low as 20 mL) can yield diagnostic quality CT aortograms in patients with severe renal insufficiency 6.
Prior Contrast Reactions
- Severe allergic reactions to iodinated contrast represent a relative contraindication, but CT aortography can still be performed with appropriate precautions 1.
- Only patients with previous moderate or severe adverse reactions require prophylaxis with corticosteroids and antihistamines 7.
- Life-threatening anaphylactoid reactions are not true allergies to contrast media, and "iodine allergy" is not a contraindication 8, 7.
- MR angiography should be substituted when CT cannot be performed due to contrast allergy 1.
Alternative Imaging When CT Aortography is Contraindicated
When Both CT and MR Contrast are Contraindicated
- Catheter arteriography becomes the primary option when both CTA (due to significant renal dysfunction) and MRA (due to severe renal insufficiency, cardiac pacemakers, or claustrophobia) are contraindicated 1.
- The combination of CT with lower contrast loads via intra-arterial injection may decrease CIN risk compared to intravenous administration 1.
- Non-contrast CT provides limited information but can identify calcifications and gross anatomic abnormalities 1.
MR Angiography Considerations
- MRA is the optimal substitute when iodinated contrast is contraindicated 1.
- Gadolinium-based MRA is contraindicated in patients with severe renal insufficiency (GFR <30 mL/min) due to risk of nephrogenic systemic fibrosis 1, 9.
- Non-gadolinium MRA techniques must be available if gadolinium cannot be used 1.
Specific Clinical Scenarios
Pregnancy and Lactation
- Iodinated contrast is not contraindicated in pregnancy or breast-feeding, though theoretical risks should be weighed against clinical necessity 8, 7.
- There is no evidence of harm to the fetus or infant from iodinated contrast 8.
Other Conditions NOT Requiring Special Precautions
- Hyperthyroidism, acute pancreatitis, and pheochromocytoma do not require specific measures or represent contraindications 7.
- Atopic conditions are not contraindications and do not require prophylaxis 7.
Common Pitfalls to Avoid
- Failing to assess current renal function before contrast administration is the most critical error 4, 3, 2.
- Using calculated GFR (via MDRD formula) rather than serum creatinine alone provides more accurate risk assessment 7.
- Withholding necessary contrast-enhanced studies when benefits outweigh risks—iodinated contrast should not be withheld if a contrast-enhanced study is necessary and there is no alternative 5.
- Not providing adequate hydration (12-16 mL/kg body weight of 0.9% sodium chloride) before and after contrast administration in at-risk patients 7.
- Continuing nephrotoxic medications (NSAIDs, metformin, aminoglycosides) during the peri-procedural period in patients with renal impairment 3, 2.