Introduction:
Netrin-1 (NTN-1) is an anti-inflammatory protein secreted by proximal tubule epithelial cells in reaction to hypoxic or toxic injury. We determined the utility of urinary NTN-1 as an early marker for detecting acute kidney injury (AKI) in patients after cardiac surgery.

Material and methods:
Our study included 40 children at age 1-36 months and 20 healthy controls. We measured serum creatinine and urinary NTN-1 in patients who underwent cardiac surgery with cardiopulmonary bypass (CPB).

Results:
Urinary NTN-1 was higher in the study group than in the control group. The detection rate of urinary NTN-1 was higher before surgery than 6 and 24 h after (55%, 27.5%, and 32.5%, respectively). We found no correlations between NTN-1 at any point and ΔeGFR, decline in eGFR, or AKI after 48 h. The initial NTN-1/creatinine ratio negatively correlated with ΔGFR (r = –0.36, p = 0.031), NTN-1/creatinine ratio after 24 h did not correlate with aortic clamping time, CPB time, ΔGFR. In our study, AKI occurred in 12.5% of patients and none required renal replacement therapy (RRT). The occurrence of AKI correlated with CPB time (r = 0.35, p = 0.027) and aortic clamping time (r = 0.44, p = 0.005). NTN-1 concentration and NTN-1/creatinine ratio in the AKI group were not significantly higher preoperatively and 24 h post-surgery than in patients without AKI.

Conclusions:
The role of urinary NTN-1 in children after cardiac surgery as an early marker of AKI was not confirmed. No factors affecting the NTN-1/creatinine ratio were found in the study group. Patients who have longer CPB time and aortic clamping time belong to the high-risk group of AKI after surgery.