Impact of liberal versus restrictive fluid management on acute kidney ınjury after nephrectomy: a randomised controlled trial with cystatin C evaluation.

BACKGROUND: This study aimed to compare the effects of liberal versus restrictive intraoperative fluid management strategies on the development of acute kidney injury (AKI) following partial or radical nephrectomy. Additionally, we evaluated the diagnostic performance of serum cystatin C as an early biomarker for AKI. METHODS: This prospective, randomised controlled trial included 73 adults undergoing elective unilateral nephrectomy. Patients were assigned to receive either a liberal (7 mL/kg/h) or restrictive (3 mL/kg/h) intraoperative crystalloid fluid regimen. The primary outcome was the incidence of AKI based on Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Serum creatinine, blood urea nitrogen (BUN), serum urea, and estimated glomerular filtration rate (eGFR) were measured preoperatively, at 24 and 48th hours postoperatively, and on postoperative day 5. Serum cystatin C was measured preoperatively and at 48th hours. Secondary outcomes included eGFR changes and the predictive accuracy of biomarkers. RESULTS: AKI occurred significantly more frequently in the restrictive group than in the liberal group (75% vs 40.4%; p = 0.001). The restrictive group experienced a more pronounced reduction in eGFR (- 27.49 ± 20.6 vs - 14.87 ± 16.93 mL/min/1.73 m2; p = 0.006) and a greater increase in serum cystatin C levels postoperatively (ΔCysC: 0.28 ± 0.14 vs 0.15 ± 0.13 mg/L; p = 0.01). No significant differences were observed between the groups in terms of postoperative serum creatinine or BUN levels. CONCLUSIONS: A liberal intraoperative fluid strategy significantly reduced the incidence of AKI following nephrectomy. Serum cystatin C outperformed creatinine in the early detection of AKI, suggesting a liberal fluid strategy may be preferable to reduce AKI risk, and cystatin C may serve as a useful early AKI biomarker. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT06256120 (Registered on 26 December 2023).