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.
Without functioning white matter, the brain could be like a group of people in proximity to each other but unable to communicate with each other. After centuries of being recognized but not well understood, white matter gained growing importance as neuroscientists turned to the study of brain-behavior relationships.