The incidence of renal cell carcinoma is increasing and in 2008 it is estimated that over 51,000 new renal cancers will be diagnosed in the United States. To preserve renal function, urologists commonly remove the diseased segment of the kidney (partial nephrectomy) instead of removing the entire kidney (radical nephrectomy). While the benefit of preserving function in patients with renal cell carcinoma has become clear, optimal preservation techniques are yet to be determined. Specifically, the role of hypothermia during partial nephrectomy has been inadequately studied despite theoretical benefit. The investigators objective is to assess the effectiveness of renal hypothermia during partial nephrectomy. The investigators hypothesis is that renal hypothermia during partial nephrectomy results in improved post-operative renal function compared to warm ischemia.