Complete (radical) nephrectomy is surgery to remove all of a kidney. Kidney-sparing surgery (partial nephrectomy) removes part of a kidney.
White matter signal changes on the MRI essentially means that on the MRI, the white matter showed some scattered bright spots. White matter in the brain refers to the fiber tracts that carry information to and fro from the brain. My first question when somebody asks me what next and what does this mean is to ask them why was the MRI done in the first place.
The impressive growth of modern neuroimaging has let us depict white matter and its functional specializations in increasingly elegant detail. Today, there is an explosion of information on white matter, its role in normal brain function, and its relevance to human illness.