CT assessment of residual contrast medium in the kidney 12-24 hours after angiography

Residual contrast medium in the kidney on delayed film is sometimes reported in patients with problems in the urinary system following the administration of contrast medium. However, we frequently found residual contrast medium in the kidney of patients with normal renal function on delayed CT after angiography. Thus we carried out CT examination 12-24 hours after angiography with four kinds of contrast media to prospectively study the incidence of residual contrast medium in the kidney. Residual contrast medium in the kidney was observed on delayed CT in 286 of 536 patients (53%). We found a relatively higher incidence with ioxaglate (63%) and iohexol (60%) than that with iopamidol (28%) and diatrizoate (38%). The incidence of residual contrast medium in the kidney increased with the dose of contrast medium administered expect in the case of iopamidol. The influence of hepatobiliary and renal function on residual contrast medium in the kidney was examined. We found a higher incidence of residual contrast medium in the group with abnormal hepatobiliary function than in the group with normal function. This implied that the hepatobiliary pathway is an important tract in the excretion of contrast medium even if the dose of excretion is small. A high frequency of residual contrast medium in the kidney was recognized on delayed CT not only in the renal dysfunction group but also in the normal renal function group. We suggest that residual contrast medium in the kidney is a normal phenomenon on delayed CT. (author)