US, CT and MR imaging characteristics of nephroblastomatosis.

OBJECTIVES

To describe the imaging features of nephroblastomatosis with US, CT and MR, to point out characteristics of differentiation between nephrogenic rests (NR) and Wilms' tumour (WT) and to determine the most appropriate imaging modality.

MATERIALS AND METHODS

We reviewed the US, CT and MR images of 29 cases of histopathologically confirmed nephroblastomatosis sent to our department for reference evaluation (German nephroblastoma study). The series included 17 kidneys with NR, 6 kidneys with WT and 32 kidneys with both NR and WT.

RESULTS

NR presented as multinodular, peripheral, cortical lesions, the diffuse form of distribution being less common. Foci were homogeneous and of low echogenicity, density or signal intensity. The lesions were most clearly depicted with contrast-enhanced CT and T1-weighted (T1-W) MR images. Lesions smaller than 1 cm were rarely identified by US. The most reliable criterion to differentiate NR from WT was their homogeneity.

CONCLUSIONS

Contrast-enhanced CT and T1-W MR images are of similar potential and superior to US in the diagnosis of nephroblastomatosis. Due to the significant radiation dose of serial CT, MR imaging should be the method of choice wherever it is available. The cost-effectiveness and availability of US makes it ideal for serial follow-up of known lesions.