Imaging and kidney disease
For patients with kidney disease taking metformin and who require iodinated contrast there is a low absolute risk of the patient developing lactic acidosis.1
Consider the risks of lactic acidosis and the potential benefits of the procedure.1 The decision to use iodinated contrast in a patient with kidney disease using metformin should be made in consultation with the patient’s referring doctor or kidney physician.1
- Patients with kidney disease: withhold metformin for at least 48 hours starting on the day of the contrast study. Reassess kidney function before starting metformin again.
- Patients with normal kidney function: it is not required to withhold metformin pre-procedure or re-check kidney function post-procedure, provided that only a moderate amount of contrast is used (≤ 100 mL).
Iodinated contrast–induced nephropathy2
Iodinated contrast–induced nephropathy is defined as impairment of kidney function indicated by a rise in serum creatinine by more than 25% within 3 days of contrast administration and in the absence of another aetiology.
Intravenous contrast mediums carry an overall risk of contrast-induced nephropathy of 1.2–2.7%. Most cases recover spontaneously within 14 days although a minority can progress to chronic kidney failure.
The factors that increase the risk of contrast media-induced nephropathy with a marked decline in kidney function include:
- Underlying kidney disease
- Age > 70 years
- Use of nephrotoxic medications
- Cardiac failure
- Previous kidney surgery
- Cirrhosis of the liver
- Intra-arterial contrast administration, large doses of contrast and repeated doses of contrast
Gadolinium-containing contrast agents
Gadolinium-containing contrast agents have recently been associated with the development of nephrogenic systemic fibrosis.3
Gadolinium containing contrast media should be used with caution in patients with kidney failure, identify patients at risk of developing nephrogenic systemic fibrosis by using the RANZCR guidelines on the use of gadolinium-containing MRI contrast agents:4
- Magnetic resonance imaging (MRI) contrast agents should be used only when the benefits from their use will exceed the (usually very small) risk.
- Consider other imaging modalities like a non-contrast MRI, computed tomography, or ultrasound that will provide the desired diagnostic information at a lesser risk.
- Use the lowest dose that is diagnostically adequate.
- All patients should have screening for kidney disease. The following set of questions can be asked:
- Is the patient's age >60?
- Is the patient hypertensive?
- Does the patient have diabetes mellitus?
- Does the patient have a history of kidney disease (including kidney transplant, solitary kidney)?
- Is the patient in the immediate (within 1 month or less) pre or post-operative period of a liver transplant?
- Is the patient currently experiencing an acute deterioration in kidney function? Note that serum creatinine may not stabilise until 7-10 days after an acute insult.
- Royal Australian and New Zealand College of Radiologists. RANZCR Guidelines for iodinated contrast administration - 2009 Edition., 2009. http://www.ranzcr.edu.au/resources/policy-library/guidelines (accessed 4 June 2013).
- Government of Western Australia - Department of Health. Diagnostic imaging pathways - contrast Agents. Iodinated contrast for CT scans. 2013. http://www.imagingpathways.health.wa.gov.au/index.php/about-imaging/diagnostic-imaging-pathways-overview-contrast-agents/iodinated-contrast-for-ct-scans#I3 (accessed 4 June 2013).
- Government of Western Australia - Department of Health. Diagnostic imaging pathways - contrast agents. Gadolinium for MRI scans. 2013. http://www.imagingpathways.health.wa.gov.au/index.php/about-imaging/diagnostic-imaging-pathways-overview-contrast-agents/gadolinium-contrast-for-mri-scans#g1 (accessed 4 June 2013).
- Royal Australian and New Zealand College of Radiologists. RANZCR Guidelines on the use of gadolinium-containing MRI contrast agents. October 2009. http://www.ranzcr.edu.au/resources/professional-documents/guidelines (accessed 18 June 2013).