Contrast agents can result in minor or major allergic reactions. The overall reaction rate to non-ionic agents is 0.2-0.7% with fatalities <1:40,000. Gadolinium had a reaction rate of <0.7%. Contrast induced acute kidney injury occurs in 3-4%, defined as an increase in serum creatinine of ≥0.5mg/dl. Patients at highest risk are those with CKD, DM, older age, dehydration, CHF and administering higher volumes of contrast. Nephrogenic systemic fibrosis (NFS) is linked to gadolinium and occurs in patients with a GFR <30ml/min/1.73m2. The incidence is estimated at 4.3/1,000 patients.
Radiation induced cancer risk occurs with more than 50mSv of radiation exposure. Compared to atomic bomb exposure, imaging exposure is focally delivered. 0.2% of cancers may be related to imaging. Background radiation exposure in the US is 3mSv/year. It is greater at higher altitudes (flying, living in Denver). The CXR dose is 0.1mSv and the x-ray airport screening results in an exposure dose of 0.00025mSv. The tumors likely are typically blood malignancies. He discussed radiation risk for follow-up of a bladder cancer patient according to NCCN guidelines. It might total 266mSv, or a 1% increased risk. For testes cancer, imaging total 160mSv or a 0.64% increase. Use of MRI scanning can decrease this. For prostate cancer, there is much less imaging, and radiation risk is probably not a significant factor. Imaging should only be done if it alters therapy, he pointed out. A final example was a patient with a small renal mass. Imaging follow-up offers options of CT with or without contrast or MRI. For pT1 tumors, the recurrence rate was 4.4%, increasing to 14% for pT3 tumors. As such, imaging frequency should be considered accordingly.
Presented by Brian Herts, MD at the American Urological Association (AUA) Annual Meeting - May 14 - 19, 2011 - Walter E. Washington Convention Center, Washington, DC USA
Reported for UroToday by Christopher P. Evans, MD, FACS, Professor and Chairman, Department of Urology, University of California, Davis, School of Medicine.