Mannitol Use During Partial Nephrectomy Prior to Renal Ischemia and Impact on Renal Function Outcomes

The purpose of this study is to determine if a medication called mannitol, can help the kidney maintain its function after kidney surgery. Mannitol is used to cause an increase in urine production (it is a diuretic). For many years, mannitol has been given to patients in the hope it would improve the kidney's circulation, and in doing so reduce the impact of the surgery on the kidney.

Mannitol is given during the surgery before the blood supply to the kidney is stopped. The blood supply to the kidney is stopped in order to minimize any blood loss during the removal of the tumor, and also to assist the surgeons view of the kidney anatomy. Once the tumor is removed the blood supply to the kidney is resumed. Sometimes a side effect of this temporary reduction in blood supply to the kidney is the loss of some kidney function. This may happen either in the short term (right away) or long term (months or years later). In studies done on animals, mannitol was able to lessen this damage to kidney function. However, no human study has ever confirmed that mannitol has the same helpful effect in humans. There is some suggestion that it may have no effect. Because sufficient research has yet to be done on humans, many surgeons do not give mannitol. A recent study, conducted at Memorial Sloan Kettering which looked back at patients who had undergone partial nephrectomies, an operation where only the portion of the kidney that contains the tumor is removed and enables the normal, unaffected portion of the kidney to be preserved. The results of this study demonstrated no significant difference in kidney function when the investigators compared patients who were given mannitol to those who were not. The investigators hope that this study will help clarify the effectiveness or not of mannitol on kidney function. During the surgery to remove the kidney tumor, patients will receive either mannitol or a placebo. A placebo, is a harmless medication that has no effects. The impact of mannitol compared to the placebo will be assessed by routine blood tests and imaging (kidney scan) 6 months after your surgery.