To evaluate whether ultrasonography was inferior in detecting the size of a renal mass preoperatively because of the increased attention on the harmful effects of ionizing radiation in medical imaging.

A prospectively maintained database was reviewed of all patients who underwent renal ultrasonography before definitive therapy for the renal mass. Every patient who underwent ultrasound imaging also underwent computed tomography (CT) or magnetic resonance imaging (MRI), or both, before treatment. The size of the largest tumor identified per imaging modality was compared among the modalities using correlation and analysis of variance.

A total of 116 patients underwent ultrasound imaging before therapy. Of these patients, 80 also underwent MRI, 66 underwent CT, and 38 underwent all 3 modalities before treatment. The average pathologic tumor size for the entire cohort was 4.45 cm (range 1-13). The size differences between CT and MRI compared with ultrasound were small (<3.5%). Compared with MRI and CT, ultrasound was also well correlated (P < .001 and P < .001). In patients who underwent all 3 imaging modalities, no difference was found in the average tumor size (P = .896).

Ultrasound imaging does not appear to be inferior to CT and MRI in the imaging of renal masses. This is useful in reducing the costs and levels of radiation exposure for the long-term follow-up of patients receiving active surveillance.