Radiation therapy patients may require the administration of contrast media during radiation therapy imaging to enhance visibility of vascular structures and organs. The administration of iodinated contrast media has a risk of renal adverse events including contrast-induced acute kidney injury (CI-AKI) and metformin associated lactic acidosis (MALA).
Definitions
Iodinated contrast media are radiocontrast agents containing iodine. These are used during medical imaging procedures, including radiation therapy imaging, to enhance visibility of vascular structures and organs. They are administered through various methods, but the most common ones include intravenous injections, oral intake, and on occasion, intracavity insertion.
Contrast induced acute kidney injury (CI-AKI) describes a sudden, noticeable decline in kidney function following the intravascular administration of iodinated contrast medium in the absence of an alternative causative aetiology.r It can also be referred to as contrast induced nephropathy.
Metformin associated lactic acidosis (MALA) is the build-up of lactate in the bloodstream and can be fatal. Patients taking metformin (an oral antidiabetic agent) can develop MALA following IV contrast administration. Metformin is excreted primarily by the kidneys and continued intake of metformin in the setting of renal failure may result in a toxic accumulation of this drug and lead to MALA.r
Incidence/prevalence
CI-AKI
The incidence of CI-AKI from iodinated contrast administration is >2% in the general population.r However, the incidence is as high as 8-16% in patients >60 years old, and 20-30% in high-risk groups.r
MALA
MALA is exceedingly rare, estimated to occur at a rate of 0 to 0.084 cases per 1,000 patient-years. Patient mortality in reported cases is approximately 50%.r
Onset/duration
CI-AKI
Kidney dysfunction that is linked with the administration of iodinated contrast media is acute, usually occurring within 2-3 days, most cases are completely reversible within 2-4 weeks. Kidney dysfunction developing up to seven days post contrast media administration is expected to be considered CI-AKI if it is not attributable to any other cause of renal failure.r
MALA
The onset of lactic acidosis can be rapid, or progressive over several days.r
Risk factors
CI-AKI
Numerous studies have attempted to isolate risk factors for CI-AKI. There is consensus that pre-existing severe kidney dysfunction is the most significant risk factor.rrr Refer to table 1.0: RANZCR risk classifications for CI-AKI.r
Table 1.0: Risk of CI-AKI based on eGFRr
eGFR |
Risk of CI-AKI |
>45 mL/min/1.73 m2 |
Likely non-existent |
30-45 mL/min/1.73 m2 |
Very likely to be low or non-existent |
<30 mL/min/1.73 m2 (severe renal function impairment)
OR
Actively deteriorating renal function (acute kidney injury) |
Highest risk of CI-AKI |
Other proposed risk factors, include:rrrrr
- dehydration
- co-morbidities (e.g. diabetes mellitus, cardiovascular diseases, hypertension)
- diuretic use
- advanced age
- hyperuricemia
- multiple iodinated contrast medium doses in a short time interval (<24 hours).
It is reported that there is a lower risk of CI-AKI when low-osmolar contrast media is used.r
MALA
MALA is more likely to occur in patients who have acute kidney dysfunction from events such as dehydration, vomiting, diarrhoea or surgery, and especially in elderly persons who have a reduced estimated glomerular filtration rate (eGFR).rrrrrr
Patients with stable kidney function (i.e. eGFR of > 30mL/min/1.73 m2) have minimal risk of developing MALA as a direct consequence of contrast media.