Mannitol is often used as a renoprotective agent in nephron-sparing surgery (NSS) prior to renal vessel clamping. Although there is some recent evidence questioning its role, these studies used a fixed dose of mannitol and studied a heterogeneous group that included both laparoscopic and open NSS. This trial aimed to investigate whether renal-functional outcomes in patients undergoing laparoscopic NSS are equivalent in patients receiving weight-based mannitol and those administered placebo.

In this prospective, randomized, double-blinded, placebo-controlled trial, 100 patients who underwent laparoscopic NSS with an estimated glomerular filtration rate (eGFR) > 45 ml/min/1.73 m2 were randomized to receive either weight-based mannitol (0.25 g/kg) or placebo (0.9% saline) 30 min prior to vessel clamping. Standardized anesthesia and fluid management protocols were followed. A predefined equivalence margin of 8 units of eGFR was used to define equivalence between the groups. The primary outcome was the difference in eGFR between the two groups at 6 months after surgery. The secondary outcomes were the difference in eGFR on days 2 and 10, blood loss, and complications between groups.

Baseline characteristics were comparable between the groups. The mean difference in eGFR of the two groups at 6 months from baseline was 2.25 (95%CI − 1.9, 6.4), which was within the margin for equivalence. Similarly, the mean difference (95% CI) for eGFR at day 2 and day 10 from the baseline was 0.58 (95% CI − 5.5, 6.6) and -0.38 (95%CI − 4.9, 4.1), respectively, suggesting equivalence between the groups. Complication rates were comparable between the two groups.

Intraoperative mannitol administration was equivalent to placebo for renal-functional outcomes (eGFR) of patients undergoing laparoscopic NSS suggesting that this practice can be discontinued.