Urinary [TIMP-2]/[IGFBP7] Ratio (Nephrocheck ® akiscore ®) as a biomarker of “subclinical” acute kidney injury after robotic partial nephrectomy

Aim of the study: Acute kidney injury (AKI) after partial nephrectomy (PN) is based on postoperative variations in serum creatinine and urinary output, which represent suboptimal parameters for early diagnosis of AKI in routine clinical practice. Of note, current evidence on the triggers of early renal injury after PN is still sparse and novel biomarkers are needed to allow correction of any reversible factor of renal damage. In this scenario, “subclinical” AKI is ea new entity is emerging within the spectrum of AKI syndrome, diagnosed by elevation of markers of tubular damage with normal level of serum creatinine and urinary output. Aim of our study was to explore the role of a urinary [TIMP-2]/[IGFBP7] ratio (NephroCheck®) as a biomarker of subclinical AKI. Materials and methods: We prospectively enrolled adult patients with a sporadic cT1N0M0 renal mass, contralateral functioning kidney, and no preoperative CKD (eGFR >45ml/min/1,73m2) undergoing robotic enucleation by a single experienced surgeon between July 2017 and February 2018. We evaluated urinary levels of Nephrocheck® before surgery and 4,12 and 24 h after PN. The product of the urinary concentration of [TIMP-2]x[IGFBP7] was assessed by a commercially available immunoassay (NephroCheckTM). Based on previous studies in different settings, we considered NephroCheck values >0.3 as cutoff for moderate risk of AKI. Results: Overall, 40 patients were enrolled. Of these, 16 (40%) experienced AKI according to standard criteria. Of 24 not experiencing AKI, 14 (58.3%) of the cohort patients showed a post-operative time point (4 or 12 or 24 h or more than one time measurements) NephroCheckTM >0.3.In the overall population, there was no significant difference in preoperative proportion of patients with Nephrocheck >0.3 between patients with and without AKI ( p = 0.1). On the contrary, the proportion of patients with positive AKI risk score (Nephrocheck >0.3) (Figure 1a,b) was significantly higher at 4 h, 12 h and 24 h after robotic enucleation in patients with AKI as compared to patients without AKI. A sensitivity analysis stratified according to preoperative Nephrocheck test (<0.3 Figure 1c and >0.3 Figure 1d) showed that the proportion of patients with Nephrocheck >0.3 was significantly higher at 4 h, 12 h and 24 h in patients with AKI as compared to patients without AKI only in the subpopulation of patients with preoperative Nephrocheck >0.3. Discussion: If considering NephroCheckTM as a biomarker of subclin- ical AKI, a non-negligible proportion of patients can be classified as experiencing “sub-clinical AKI”, as they did not experience AKI according to standard clinical criteria but showed positivity of the Nephrocheck test (>0.3). Further studies are needed to evaluate if this subgroup of patients will experience a decline in eGFR at mid-long term follow-up.