The effects of warm ischaemia time on renal function after laparoscopic partial nephrectomy in patients with normal contralateral kidney.

PURPOSE: To assess the effects of warm ischaemia time (WIT) on renal function after laparoscopic partial nephrectomy (LPN) for renal masses in patients with a normal contralateral kidney. METHODS: From October 2006 to December 2008, 53 patients treated with LPN were enrolled in this prospective study. Effective renal plasma flow (ERPF) was estimated with 99mTc-mercaptoacetyltriglycine renal scintigraphy before the intervention and after 3 and 12 months. Multiple linear regression analysis was used to assess the effects of demographic and operative variables on postoperative renal function. Logistic regression analysis was used to evaluate the associations between the same variables and a ≥20% reduction in postoperative ERPF compared with baseline (defined as significant loss of renal function-LRF). ROC curve analysis was used to identify potential ischaemia time cut-off points. RESULTS: Fifty-one patients were eligible. The mean lesion size was 30 mm, and the mean WIT was 21.9 min. Longer WIT was associated with lower postoperative ERPF values (P < 0.001). A logistic regression model confirmed that longer WITs were significantly associated with ERPF decreases ≥20% (OR 1.454 and 1.741, for each 1-min increase, respectively). ROC analysis identified 25 min as a 'safe' cut-off for WIT (AUC 0.874, P < 0.001). Postoperative ERPF differences between the two groups (WIT ≤25 and >25 min) were significant. CONCLUSIONS: Longer WIT was associated with LRF, as estimated with renal scintigraphy. LRF occurred within 3 months and remains stable until the 12th month after LPN. Every effort should be made to minimise warm ischaemic intervals during LPN, and the limit of 25 min should be not exceeded.