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.