Iodinated contrast (CT)
Modern low-osmolar iodinated contrast media are safe for the large majority of patients. Renal screening (typically a recent serum creatinine and eGFR) is based on risk factors rather than universal screening; many institutions skip the lab in healthy ambulatory patients with no risk factors. Contrast-induced kidney injury risk has been substantially reassessed in the last decade and is now considered lower than previously believed.
Prior contrast reaction is the most important history to capture. Patients with a documented prior moderate or severe reaction generally receive a premedication regimen (corticosteroid and antihistamine) or have the study performed without contrast if the indication allows.
Gadolinium contrast (MRI)
Group II and Group III gadolinium-based contrast agents are the standard for MRI in our network. Renal screening for gadolinium has been simplified — the historical concerns about nephrogenic systemic fibrosis are now considered very low with these agents, even in patients with significantly reduced kidney function.
Gadolinium reactions are rare. As with iodinated contrast, a documented prior reaction is the most important piece of history to provide on the order.
When contrast is typically needed
- Suspected tumour, infection, or active inflammation (most body regions).
- Post-operative spine — and/or evaluation of recurrent vs scar tissue.
- Vascular questions — CTA chest, CTA abdomen/pelvis.
- Bowel pathology — CT abdomen/pelvis with IV contrast.
- Most CT abdomen/pelvis indications other than renal stone protocol.
When contrast is typically not needed
- Routine non-post-op lumbar spine MRI.
- Most musculoskeletal MRI of the extremities for internal derangement.
- Non-contrast head CT for trauma, acute haemorrhage, hydrocephalus.
- Renal stone protocol CT (specifically non-contrast).
Pregnancy and lactation
Iodinated and gadolinium contrast are generally avoided in pregnancy unless the clinical need is essential and there is no acceptable alternative — that decision is coordinated with the obstetrician. Breastfeeding can continue without interruption after both iodinated and gadolinium contrast based on current evidence.
Metformin
For most patients with stable renal function, metformin does not need to be held around iodinated contrast administration. The exceptions are patients with significant baseline renal impairment or those who develop contrast-associated acute kidney injury, where metformin is held until renal function is reassessed.
Ordering with Precise
If you are uncertain whether a study needs contrast, order the version your clinical question suggests and our protocolling radiologists will adjust at intake. Reach our protocol line during business hours through the provider portal or by phone.
Questions referring offices ask first.
Do I need a recent creatinine before ordering CT with contrast?
For ambulatory patients with no risk factors, many institutions no longer require routine screening. We follow current practice — provide a recent value if available, and we will screen at intake.
Can a patient with a prior contrast reaction still have contrast?
Often yes, with appropriate premedication and a careful weigh-up. Document the prior reaction in detail on the order so we can plan appropriately.
Does the patient need to stop breastfeeding after contrast?
No. Current evidence supports continuing breastfeeding without interruption after both iodinated and gadolinium contrast.
Educational reference for referring providers. Not a substitute for clinical judgement or the current official appropriateness criteria. References imaging modalities offered by Precise; modalities not in our network are out of scope.