Long warm ischemia time leads to kidney function loss

Paris-In patients undergoing partial nephrectomy, warm ischemia time greater than 25 minutes is associated with greater loss of kidney function, according to a recent report.

Warm ischemia time (WIT) is an important determinant of kidney function recuperation after partial nephrectomy. Italian investigators used renal scintigraphy to evaluate the long-term effects of warm ischemia during laparoscopic partial nephrectomy (LPN) on renal function in patients with a normal contralateral kidney.

In this prospective study, the kidney function of 54 patients who underwent LPN was evaluated, with a minimum follow-up of 4 years. First author Francesco Porpiglia, MD, of the University of Turin San Luigi Gonzaga Hospital, Orbassano, Italy, presented the results at the European Association of Urology annual congress in Paris.

Split renal function (SRF) and effective renal plasma flow (ERPF) were evaluated by renal scintigraphy preoperatively, at the third and 12th postoperative month, and then yearly for 4 years following LPN.

WIT >25 minutes linked with loss of function

The results showed that the loss of kidney function was greater in group B (WIT >25 minutes). Moreover, the recorded kidney damage was early and irreversible, but not progressive. SRF and ERPF significantly decreased when compared to baseline conditions. SRF and ERPF differentials were stable over 4 years.

"When looking at the overall patient collective, one sees a decrease in SRF over the first 3 months, which then more or less stabilizes over time. The same can be seen with ERPF," Dr. Porpiglia observed.

After patient stratification, Dr. Porpiglia noted that group B revealed a significant difference from baseline values 3 months postoperatively, as seen by the sharp decrease in SRF compared to group A. Only patients with a greater WIT had a significant impairment of renal function, he said.

SRF and ERPF were different at every time point between the groups, except at baseline. The differential between renal function at every time point with respect to baseline was higher in group B, indicating a greater loss of renal function in this group.

Tumor size a factor?

A German urologist who attended Dr. Porpiglia's presentation observed that tumor size might have influenced renal functional loss.

"We have heard that the loss of renal parenchyma is related to the tumor size and is responsible for the loss of renal function. Maybe the tumors were bigger in group B and accounted for the loss of renal function," he argued.

Dr. Porpiglia explained that there was no difference between the two groups with regard to tumor size. He said that, in his experience, neither the tumor diameter nor the amount of healthy tissue was significantly related to loss of renal function.

Dr. Porpiglia confirmed the results of other studies in which a WIT of 25 minutes was a good determinant and cut-off for renal function. He noted, however, that one limitation to his study was the small sample size. Nevertheless, his study was one of the largest long-term prospective series thus far reported, he said.