The impact of warm ischaemia on renal function after laparoscopic partial nephrectomy

Authors from Cleveland assessed the impact of warm ischaemia on renal function, using their large database of laparoscopic partial nephrectomies for tumour. While agreeing that renal hilar clamping is essential for precise excision of the tumour, and other elements of the operation, the authors indicate that warm ischaemia may potentially damage the kidney. However, they found that there were virtually no clinical sequelae from warm ischaemic of up to 30 min. They also found that advancing age and pre-existing renal damage increased the risk of postoperative renal damage.

To assess the effect of warm ischaemia on renal function after laparoscopic partial nephrectomy (LPN) for tumour, and to evaluate the influence of various risk factors on renal function.

Data were analysed from 179 patients undergoing LPN for renal tumour under warm ischaemic conditions, with clamping of the renal artery and vein. Renal function was primarily evaluated in two groups of patients: 15 with tumour in a solitary kidney, who were evaluated by serial serum creatinine measurements; and 12 with two functioning kidneys undergoing unilateral LPN, and evaluated by renal scintigraphy before and 1 month after LPN to quantify differential renal function. Also, in all 179 patients, mean serum creatinine data at baseline, 1 day after LPN, at hospital discharge, and at the last follow-up were provided as supportive evidence. Logistic regression analyses were used to assess the effect of various risk factors on renal function after LPN, i.e. patient age, baseline serum creatinine, tumour size, solitary kidney status, duration of warm ischaemia, pelvicalyceal suture repair, urine output and intravenous fluids during LPN.

In the group of patients with a solitary kidney the mean warm ischaemia time was 29 min, kidney parenchyma excised 29%, and serum creatinine at baseline, discharge, the peak after LPN and at the last follow-up (mean 4.8 months) 1.3, 2.3, 2.8, and 1.8 mg/dL, respectively. One patient (6.6%) required temporary dialysis. In the second group, assessed by renal scintigraphy, the function of the operated kidney was reduced by a mean of 29%, commensurate with the amount of parenchyma excised. For all 179 patients, a combination of age > or = 70 years and a serum creatinine level after LPN of > or = 1.5 mg/dL correlated with a higher serum creatinine after LPN. On logistic regression, baseline serum creatinine and solitary kidney status were the only variables significant for serum creatinine status after LPN.

The bloodless field provided by renal hilar clamping is important for precise tumour excision, pelvicalyceal suture repair and securing parenchymal haemostasis during LPN. However, renal hilar clamping causes warm ischaemia. These data indicate that the clinical sequelae of warm ischaemic renal injury of approximately 30 min are minimal. Advancing age and pre-existing azotaemia increase the risk of renal dysfunction after LPN, especially when the warm ischaemia exceeds 30 min.