Angiography is an exam used to see the body's arteries and veins using X-rays and a contrast medium. It allows the identification of blockages, narrowings or malformations of blood vessels.

Does contrast media harm the kidneys?

Iodinated contrast media can damage the kidneys, especially in patients with diabetes, renal insufficiency or advanced age. A safe alternative exists: CO₂ angiography.

What is CO₂ angiography?

CO₂ angiography uses carbon dioxide instead of iodinated contrast media. CO₂ has no renal toxicity and is naturally eliminated through the lungs within minutes.

Where can I have CO₂ angiography performed in Italy?

In Italy there are over 100 facilities equipped with CO₂ angiography technology. To find the nearest facility you can write to scrivi@angiodroid.com.

Patient Guide: Angiography, Contrast Media and the CO₂ Alternative

Starting point

What is angiography and what is it for?

Angiography is a medical exam used to see the body's arteries and veins from the inside. It allows doctors to identify blockages, narrowings (stenosis), aneurysms or malformations of blood vessels — problems that a regular CT scan or ultrasound cannot always show in sufficient detail.

It is mainly used to study the leg arteries (lower limb arteries), heart arteries (coronary angiography), renal arteries, and those of the abdomen and aorta.

How does it differ from a CT scan or MRI?

→CT scan with contrast: uses X-rays and iodinated contrast media injected into an arm vein. The exam lasts a few minutes and does not require vessel access.
→MRI: uses magnetic fields, not X-rays. The contrast medium (gadolinium) differs from iodinated contrast and has a different renal risk profile.
→Angiography: more specific and precise for vessels. Requires small skin access (usually the groin or wrist) and allows direct intervention — not just imaging.

💡 Important: only angiography allows diagnosis and treatment at the same time — for example opening a blocked artery (angioplasty) or placing a stent.

Step by step

How is angiography performed? Does it hurt?

Angiography is performed by a specialist physician — an interventional radiologist or a vascular surgeon — in an equipped operating or angiography suite.

1

Preparation An IV line is inserted and your blood pressure and heart rate are monitored. The access area (usually the groin) is disinfected and prepared.
2

Local anaesthesia A local anaesthetic is injected into the access area — similar to a dentist's anaesthetic. You'll feel an initial pinch, then the area becomes numb.
3

Catheter insertion Through a small puncture, a very thin flexible tube (catheter) is inserted into the artery. You won't feel pain because the area is numbed.
4

Contrast media injection Contrast media (iodinated or CO₂) is injected through the catheter. You may feel a warm sensation or mild discomfort, but no intense pain.
5

Image acquisition Special X-rays capture the vessels in real time — the contrast media makes them visible. The doctor sees everything on a monitor during the procedure.
6

End and recovery The catheter is removed and the access point is manually compressed for a few minutes. You'll lie down for a few hours before being able to get up.

How long does it take? From 30 minutes to 2 hours depending on complexity. For a simple diagnostic angiography, you often go home the same day. For therapeutic procedures (angioplasty, stenting), a 1-2 day hospital stay may be necessary.

What you need to know

Can iodinated contrast media damage the kidneys?

Yes — and this is the most important thing to know before undergoing angiography or a contrast CT scan.

Iodinated contrast media is filtered by the kidneys and eliminated through urine. In some patients this process overburdens the kidneys and can cause acute kidney injury, medically known as AKI (Acute Kidney Injury) or contrast-induced nephropathy.

⚠ Possible consequences of contrast-induced kidney damage

Temporary or permanent worsening of renal function
Need for dialysis in the most severe cases
Prolonged hospital stay
In people with already impaired kidneys: further reduction of residual function

Besides renal risk, iodinated contrast media can cause allergic reactions — from mild (itching, redness) to severe (breathing difficulties). If you've had a reaction in the past, always report it before the exam.

⚠ If you've had reactions to contrast media, iodine or shellfish before, talk to your doctor before the exam. Premedication or, better still, an alternative such as CO₂ may be indicated.

Your situation

Who is most at risk of contrast-induced kidney damage?

Not all patients carry the same risk. Certain conditions significantly increase the likelihood that iodinated contrast media will damage the kidneys:

⚠Chronic kidney disease (CKD) — especially with GFR below 60, and even more so below 30
⚠Diabetes mellitus — increases risk even when kidneys still appear normal
⚠Advanced age — renal function tends to decline with age even without a formal diagnosis
⚠Dehydration — being poorly hydrated at the time of the exam amplifies the damage
⚠Use of NSAIDs or metformin — these medications increase the risk of kidney damage in combination with contrast media
⚠Peripheral artery disease — those with leg artery problems often also have impaired kidneys
⚠Heart failure or dehydration — reduce blood flow to the kidneys

💡 The riskiest combination is: diabetes + renal insufficiency + peripheral artery disease. If you have all three conditions together, ask your doctor explicitly whether CO₂ can be used instead of iodinated contrast media.

How is risk measured? Creatinine and GFR

Your doctor will assess your renal function through a simple blood test. The parameters to know are:

→Creatinine: a waste product that the kidneys must filter. If it's high, the kidneys are working less well.
→GFR (or eGFR): the glomerular filtration rate — indicates how much renal function you still have. Above 60 is normal; below 30 is high risk.

The safe alternative

CO₂ angiography: what is it and why is it safer for the kidneys?

CO₂ (carbon dioxide) can be used as an alternative contrast medium to iodinated liquid during angiography. Instead of a liquid, a gas is injected — the same CO₂ that your body naturally produces every day and that you exhale when breathing.

How does it work?

CO₂, being a gas, absorbs X-rays differently than blood and allows blood vessels to be seen in images. The procedure is identical to traditional angiography: same catheter, same access, same room. Only the injected contrast medium changes.

CO₂ is eliminated within minutes through the lungs, simply by breathing — with no kidney involvement whatsoever.

Characteristic	Iodinated contrast media	CO₂ angiography
Renal toxicity	Yes — AKI risk	No — zero renal toxicity
Allergic reactions	Possible	None
Elimination	By the kidneys (urine)	By the lungs (breathing)
Safety with CKD	High risk	Safe even with low GFR
Safety with diabetes	Increased risk	Safe
Years of clinical use	Decades	Over 30 years
Cost	Higher	Lower

Is it an experimental technique?

No. CO₂ angiography has been used clinically for over 30 years in specialised centres worldwide. It is recommended by the leading international interventional radiology and vascular surgery guidelines for patients at high renal risk.

In Italy there are over 100 hospital facilities already equipped with CO₂ angiography technology.

Does it have contraindications?

CO₂ is mainly indicated for lower limb, aortic and abdominal angiography. It has some technical limitations for procedures above the diaphragm (such as coronary arteries). Your specialist doctor will be able to tell you whether it's indicated for your specific case.

💡 How to ask your doctor: you can simply say — "I've read that CO₂ angiography exists and is safer for the kidneys. Is it possible to use it in my case?"

What to do

Before and after the exam: practical things to know

Before angiography

✓Have a recent blood test with creatinine and GFR — your doctor must know your renal function
✓Report all medications you are taking, especially metformin, NSAIDs, diuretics and anticoagulants
✓Report any allergies, especially to iodine or previous contrast media
✓Hydrate well in the preceding days — drink enough water
✓Ask if you need to suspend metformin (for diabetics) 48h before the exam
✓Ask explicitly whether it's possible to use CO₂ instead of iodinated contrast media

After angiography

✓Drink plenty of water in the following 24–48h to help the kidneys eliminate the contrast medium
✓Stay lying down for the time indicated by your doctor after the procedure (usually 2–4 hours)
✓Monitor the access point: small bruises are normal, but report swelling or bleeding immediately
✓If you had iodinated contrast media, have a creatinine check after 24–48h
✓Do not drive in the following 12–24h if you received sedatives

Still have doubts?

Frequently asked questions

Can I have angiography if my creatinine is high?

Yes, but it requires careful assessment. High creatinine means the kidneys are more vulnerable to iodinated contrast media. In these cases many doctors choose to use CO₂ as a safe alternative, or adopt preventive measures such as intravenous hydration before and after the procedure. The decision depends on your exact GFR value and the type of procedure required.

Is CO₂ gas in the arteries dangerous?

This is the most common concern, and it's understandable. The answer is no — if used correctly with certified automated systems. CO₂ is the gas your body naturally produces every day in large quantities. In angiography it is used in small controlled doses and is rapidly eliminated through the lungs within minutes. Modern automated injection systems ensure precise control of volumes and pressures, making the procedure safe.

CO₂ angiography: is it available at my hospital?

In Italy there are already over 100 facilities equipped with the technology to perform CO₂ angiography. Not all facilities offer it, but the network is continuously expanding. You can write to scrivi@angiodroid.com to find out which facility nearest to you performs it.

My mother is 78 and must have angiography — what risks does she face?

Advanced age is one of the main risk factors for contrast-induced nephropathy, even without a formal diagnosis of renal insufficiency. Before the exam, it's essential to check creatinine and GFR. If GFR is below 60, ask your doctor to consider CO₂ angiography. If it's below 30, CO₂ is often the recommended choice.

I'm afraid of the needle and the procedure. Is that normal?

Absolutely, and it's one of the most common concerns. Angiography is performed under local anaesthesia: the access point is made numb before any manoeuvre. You won't feel pain during the procedure, at most a sensation of pressure or warmth. If you're very anxious, talk to your doctor beforehand: in some cases a light sedative can be administered.

I'm diabetic and take metformin — do I need to stop before the exam?

Yes, if iodinated contrast media is used. Metformin combined with contrast media can increase the risk of a condition called lactic acidosis. It's usually suspended 48h before and resumed 48h after the exam, after verifying that renal function has remained stable. If CO₂ is used instead of iodinated contrast, this precaution is not necessary.

🏥 Want to know where to have CO₂ angiography?

In Italy there are over 100 facilities already equipped with Angiodroid® technology. Write to us and we'll tell you the closest one to you.

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Angiography: complete guide for patients