Comparison of radiographical imaging modalities for measuring the diameter of renal masses: is there a sizeable difference?

OBJECTIVE To determine which imaging modality (magnetic resonance imaging, MRI; computed tomography, CT; ultrasonography, US) best predicted pathological tumour size before radical or partial nephrectomy. PATIENTS AND METHODS The clinicopathological data of 776 patients who underwent radical or partial nephrectomy were retrospectively reviewed in the context of the radiological modality used for preoperative diagnosis. The maximum reported diameter of the tumour was compared with the maximum diameter of the tumour after resection. Data were analyzed by a paired Student's t-test, correlation and logistic regression analysis. RESULTS In total, 717 patients had available data for analysis, including 414 CT scans, 121 ultrasonographs and 455 MRIs. When tumour size was compared with preoperative tumour size on ultrasonography, CT and MRI, there was no significant differences between the estimated preoperative tumour size and pathological tumour size (CT: P = 0.56, MRI: P = 0.62, ultrasonography: P = 0.55). Tumour size was also well correlated with all three modalities. CONCLUSIONS All three standard renal imaging modalities appear to accurately predict pathological tumour size. These data are relevant to the interpretation and comparison of treatment strategies, such as active surveillance protocols and ablative therapy, where pathological size is not available. Furthermore, lack of inferiority of ultrasonography in predicting pathological tumour size affords opportunities for the reduction of patient radiation exposure and for cost containment.