Mild adverse events often follow contrast-enhanced CT imaging

Mild skin reactions are a not infrequent delayed adverse outcome of contrast-enhanced CT, according to a prospective study from the University of California, Davis.

A study of 539 subjects who received CE-CT with the low-osmolar contrast agent iohexol (Omnipaque) and 286 patients who underwent noncontrast CT found that 14.3% of the subjects who received contrast had a delayed adverse reaction. Only one patient receiving noncontrast CT reported an adverse event.

Patients recruited for the study had been referred for CT to examine the chest, abdomen, pelvis, head, neck, or extremity. Subjects were randomized to receive either contrast or noncontrast procedures. Their average ages were 55.6 years for the iohexol group and 52 years for the noncontrast patients. Subjects in the contrast-enhanced CT group were administered 12 mL of iohexol at 4 mL/sec. Imaging was performed at the UC-Davis Medical Center.

The results suggest to principal investigator Dr. Shaun Loh that radiologists should stay aware of the possibility of delayed reactions and the need for prevention and management.

The findings were gathered from direct observation during the hour after imaging, a mail-in questionnaire, and follow-up phone contacts at two to three days after the CT scan. The response rate was 88%.

Cutaneous reactions were the most common adverse event. They arose during about 2.7% of the enhanced procedures. The range of cutaneous responses included rashes, itching, skin redness, and swelling. The rashes typically appeared first on the face and ears, spreading to the neck, upper chest, and back before progressing overnight to the arms, Loh said.

Loh and colleagues identified 14 prospective clinical trials that consider delayed adverse events before designing their own study. Only two of these efforts included a noncontrast control group, and their results were generally equivocal with the exception of skin manifestations, he said.

The adverse-event percentage rate may have been low, but it is notable considering the number of contrast-enhanced CT studies performed at busy practices such as UC-Davis, Loh said. His department performs 3100 contrast-CT studies per week. That translates into 20 delayed reactions that warrant attention, he said.