What is contrast-induced nephropathy (CIN)?
Key Points
- Most patients recover from use of radiocontrast (a dye given during some x-rays, like CTs and angiograms) without complications
- All radiocontrast dyes are nephrotoxic (toxic to the kidneys)
- Suspect contrast nephropathy if blood creatinine increases 24-48 hours after a contrast study
- Decrease the risk of contrast nephropathy, particularly in patients at risk, by minimising the use and volume of dye and giving intravenous fluids when possible.
Contrast nephropathy is an acute kidney injury (AKI) after IV administration of radiocontrast dye and is usually temporary.
Diagnosis is based on a progressive rise in blood creatinine 24-48 hours after contrast is given. Treatment is supportive. Giving the patient intravenous saline saline before and after contrast administration may help in prevention.
Contrast nephropathy is an acute tubular necrosis caused by a radiocontrast agent, all of which are nephrotoxic. However, risk is lower with newer contrast agents.
The precise mechanism of radiocontrast toxicity is unknown.
Most patients have no symptoms. Kidney function usually later returns to normal.
How common is contrast nephropathy?
Approximately 2% of patients who receive contrast develop CIN. However, in high-risk groups, the incidence is as high as 20-30%.
Risk factors
- Older age
- Preexisting chronic kidney disease (CKD)
- Diabetes mellitus
- Heart failure
- Multiple myeloma
- High doses (e.g. > 100 mL) of a hyperosmolar contrast agent (e.g. during percutaneous coronary interventions, PCIs)
- Factors that reduce kidney blood supply perfusion, such as being dehydrated or the concurrent use of nonsteroidal anti-inflammatory drugs (NSAIDs), diuretics, or angiotensin-converting enzyme (ACE) inhibitors
- Concurrent use of other nephrotoxic drugs (e.g. aminoglycosides)
- Liver failure.
Diagnosis
- Blood creatinine measurement
- Creatinine usually begins to rise within 24 hours after the administration of contrast media, peaks between 3 and 5 days, and comes back to baseline in 7-10 days
- There is no universally accepted definition, and various criteria have been proposed. One definition is a 25% increase in creatinine from baseline within 48-72 hours after the procedure.
Chlolesterol emboli
After femoral artery catheterisation, contrast nephropathy may be difficult to distinguish from cholesterol emboli caused by renal atheroembolism (sometimes called ‘trash kidney’). Factors that can suggest cholesterol emboli include the following:
- Delay in onset of increased creatinine > 48 hours after the procedure
- Presence of other atheroembolic findings (e.g. livedo reticularis of the lower extremities or bluish discoloration of the toes; sometimes called ‘trash feet’)
- Persistently poor kidney function that may deteriorate in a stepwise fashion
- Transient eosinophilia or eosinophiluria and low C3 complement levels.
Livedo reticularis of legs and feet
Treatment
There is no specific treatment for CIN. So treatment is supportive.
Prevention
Preventing contrast nephropathy involves avoiding contrast when possible (e.g. not using CT to diagnose appendicitis); and, when contrast is necessary for patients with risk factors, using a safer solution.
When contrast is given, giving intravenous (IV) normal saline is ideal. 1 mL/kg/h should be given 6 -12 hours before contrast is given and continued for 6 to 12 hours after the procedure. For outpatient procedures, 3 mL/kg saline can be given the hour before the procedure, and 1 mL/kg of saline 4-6 hours after the procedure.
A sodium bicarbonate (NaHCO3) solution may also be infused but has no proven advantage over normal saline.
Giving IV fluids may be most helpful in patients with mild pre-existing CKD and exposure to a low dose of contrast. Fluids should be avoided in heart failure. Nephrotoxic drugs should be avoided before and after the procedure.
Acetylcysteine, an antioxidant, is sometimes given for patients at high risk but has no proven benefit.
Patients undergoing regular haemodialysis who require contrast do not need supplementary, prophylactic haemodialysis after the procedure.
Outlook
Contrast nephropathy is usually reversible, especially if diagnosed and managed promptly. However, in severe cases or in individuals with pre-existing CKD kidney disease, it can lead to the need for temporary or permanent dialysis.
Dialysis is required in less than 1% of the cases, with a raised incidence in patients who have CKD (3%) or undergoing primary percutaneous coronary intervention (PCI) for myocardial infarction (3%). However, in patients suffering from diabetes and advanced CKD, the rate of dialysis may be over 10%. 20% of CIN patients who require dialysis end up needing it permanently.
Summary
We have described what is contrast nephropathy. Preventing contrast nephropathy is important especially avoiding contrast when possible. We hope it has been helpful.
Other resource
Here is more information on contrast nephropathy.
Last Reviewed on 15 December 2023