Urine neutrophil gelatinase-associated lipocalin as a marker of acute kidney injury after kidney surgery

Purpose: We evaluated urine NGAL as a marker of acute kidney injury in patients undergoing partial nephrectomy. We sought to identify the preoperative clinical features and surgical factors during partial nephrectomy that are associated with renal injury, as measured by increased urine NGAL vs controls. Materials and Methods: Using patients treated with radical nephrectomy or thoracic surgery as controls, we prospectively collected and analyzed urine and serum samples from patients treated with partial or radical nephrectomy, or thoracic surgery between April 2010 and April 2012. Urine was collected preoperatively and at multiple time points postoperatively. Differences in urine NGAL levels were analyzed among the 3 surgical groups using a generalized estimating equation model. The partial nephrectomy group was subdivided based on a preoperative estimated glomerular filtration rate of less than 60, or 60 ml/minute/1.73 m² or greater. Results: Of 162 patients included in final analysis more than 65% had cardiovascular disease. The median estimated glomerular filtration rate was greater than 60 ml/minute/1.73 m² in the radical and partial nephrectomy, and thoracic surgery groups (61, 78 and 84.5 ml/minute/1.73 m², respectively). Preoperatively, a 10 unit increase in the estimated glomerular filtration rate was associated with a 4 unit decrease in urine NGAL in the partial nephrectomy group. Postoperatively, urine NGAL in the partial nephrectomy group was not higher than in controls and did not correlate with ischemia time. Patients with partial nephrectomy with a preoperative estimated glomerular filtration rate of less than 60 ml/minute/1.73 m² had higher urine NGAL postoperatively than those with a higher preoperative estimated rate. Conclusions: Urine NGAL does not appear to be a useful marker for detecting renal injury in healthy patients treated with partial nephrectomy. However, patients with poorer preoperative renal function have higher baseline urine levels and appear more susceptible to acute kidney injury, as detected by urine levels and Acute Kidney Injury Network criteria, than those with a normal estimated glomerular filtration rate.