Evaluation of textural changes in Wilms' tumour during chemotherapy by qualitative and quantitative ultrasonography.Sonograms of Wilms' tumours during chemotherapy were retrospectively evaluated (N=33) and compared with histopathology. Textural changes were prospectively quantified (N=6) by mean echogenicity (MEAN) and coefficient of variation (CV) of grey levels.Interobserver agreement for volume measurements was strong and for follow-up of sonolucencies moderate. Chemotherapy caused significant volume reduction and two major patterns of change in sonolucencies were observed; either increase or no change. No relationship between sonolucencies and volume changes was present. Sonolucencies yielded an underestimation of necrosis (P<0.001). Trends in MEAN and CV differed between patients.Volume was the most objective sonographic tumour response parameter. Changes in sonolucencies may provide additional information on tumour response. However, sonolucencies are not an accurate measure of total tumour necrosis. It was not possible to differentiate Wilms' tumour chemotherapy responders from non-responders by MEAN and CV.