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.
Let me try to help you both by explaining some basic facts about our brain and white matter lesions. The brain has two main types of tissue -- gray, which is composed of the brain cells and white, which consists of the long, communicating parts of the cells called axons. The axons are covered with an insulator-like substance called myelin. This is much like a cable or an electric wire covered with an insulator.