This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.
Contrast and the kidneys
Iodinated contrast, used for coronary angiography, CT scans and other imaging, can reduce kidney function in some patients. Contrast-induced nephropathy, also called contrast-associated acute kidney injury, is usually defined as a rise in serum creatinine of 25% or 0.5 mg/dL (44 µmol/L) within 48 to 72 hours. It is usually mild and temporary, but it is linked with longer hospital stays, dialysis and higher mortality.
The Mehran score
Roxana Mehran and colleagues published this score in 2004, based on more than 8,000 patients undergoing percutaneous coronary intervention:
| Risk factor | Points |
|---|---|
| hypotension (systolic under 80 mmHg for at least 1 hour, needing inotropes or a balloon pump) | 5 |
| intra-aortic balloon pump | 5 |
| heart failure (NYHA class III or IV, or history of pulmonary edema) | 5 |
| age over 75 | 4 |
| anemia (hematocrit under 39% in men, 36% in women) | 3 |
| diabetes | 3 |
| contrast volume | 1 per 100 mL |
| eGFR 40 to 60 / 20 to 40 / under 20 mL/min/1.73 m² | 2 / 4 / 6 |
Risk groups
| Score | Contrast nephropathy | Dialysis |
|---|---|---|
| 5 or less | 7.5% | 0.04% |
| 6 to 10 | 14.0% | 0.12% |
| 11 to 15 | 26.1% | 1.09% |
| 16 or more | 57.3% | 12.6% |
Example
A 72-year-old person with diabetes and an eGFR of 52, receiving 200 mL of contrast, scores 3 + 2 + 2 = 7: moderate risk, about 14% risk of contrast nephropathy and 0.12% risk of dialysis.
Prevention
- Check kidney function before the procedure.
- Hydrate patients at risk with intravenous normal saline before and after.
- Use the smallest volume of low- or iso-osmolar contrast; staged procedures can reduce the dose.
- Pause drugs that can harm the kidneys, such as anti-inflammatories, when possible.
- Check creatinine again 48 to 72 hours afterward in patients at risk.
Limits
The score was developed in the era of older contrast agents and larger doses, and in coronary procedures. Recent studies suggest that the risk after intravenous contrast for CT is lower than once thought. The score should guide prevention, not deny a needed procedure.