Late Adverse Events after Enhanced and Unenhanced MRI and CT: A Prospective Study

Abstract

Prospective evaluation of frequency of late and very late adverse events in patients undergoing enhanced or unenhanced magnetic resonance imaging (MRI) or computed tomography (CT). The imaging procedure was performed according to the protocols of the department. All patients were contacted 3days after their imaging procedure for the occurrence of late adverse events (LAEs) and a month later for the occurrence of very late adverse events (VLAEs) using a structured questionnaire. A total of 1042 (71%) among 1473 patients completed both the 3-day and 1-month questionnaire. The incidence of LAEs was significantly higher in the enhanced MRI (38%) and CT (27%) groups than unenhanced MRI (20%) and CT (16%) groups. The frequency of nausea, dizziness, abdominal pain and diarrhoea was significantly higher in the enhanced MRI group than in the MRI control group, while taste sensation was reported more frequent in the enhanced CT group than in the CT control group. The incidence of VLAEs was significantly higher in the enhanced CT (21%) than unenhanced CT group (13%). The same LAEs and VLAEs were reported in all four groups. LAEs and VLAEs were reported more often in patients with allergy in both the enhanced and unenhanced groups. The incidence of LAEs and VLAEs was higher in the enhanced groups than in the unenhanced groups. The most reported adverse events in the enhanced groups were also reported in the unenhanced groups. Patients with allergy reported LAE and VLAE more often. This suggests that adverse events may not always be caused by the contrast media.