What if extravasation does occur? How often are there severe complications?

The good news is that with most contrast extravasations prompt treatment prevents most complications. The literature recently has a few publications that address this issue. "Extravasation of nonionic iodinated contrast medium results only rarely in moderate or severe adverse effects, and these usually occur only when large volumes of contrast medium are involved." Frequency, Management, and Outcome of Extravasation of Nonionic Iodinated Contrast Medium in 69,657 Intravenous Injections Wang CL et al. Radiology 2007; 243:80-87 "In a single institution, extravasation of contrast material into the subcutaneous tissues occurred during attempted intravenous injection in less than 1% of patients,often involved large volumes of contrast material (50-150 ml) and nearly always resolved with conservative management." Frequency, Management, and Outcome of Extravasation of Nonionic Iodinated Contrast Medium in 69,657 Intravenous Injections Wang CL et al. Radiology 2007; 243:80-87