Renal tubular epithelial cells as an easily accessible biomarker for diagnosing AKI post cardiac surgery

Purpose Acute kidney injury (AKI) is a common clinical complication of cardiac surgeries. Although urinary particle analysis is useful for differentiating AKI, its value in AKI diagnosis has not yet been well described. We sought to determine the contribution of urinary particle analysis to the diagnosis of AKI. Methods Two-hundred and thirty-nine adult patients were prospectively included after cardiac surgery. The diagnostic performance of urinary particle analysis at different time points after intensive care unit (ICU) admission was evaluated. AKI was diagnosed and classified according to the KDIGO definitions. Urinary particles, including renal tubular epithelial cells (RTEC) and non-hyaline casts, Nephrocheck®, urinary alpha-1-microglobulin and urinary γ-glutamyltransferase (GGT) levels were measured at 4, 12 and 24h after ICU admission and evaluated against different endpoints. Results Of the 239 patients included, 41 (17.1%) had AKI stage 1, 118 (49.2%) had stage 2, and 16 (6.7%) stage 3. In the early postoperative period, urinary alpha-1-microglobulin and Nephrocheck® were good predictors of AKI stage ≥1 within 48h after ICU admission (primary endpoint) and AKI stage ≥2 (1^st secondary endpoint), respectively. Furthermore, at 12h and 24h after ICU admission, RTEC had the highest predictive value for AKI up to 48h after ICU admission based on serum creatinine alone and for all AKI criteria up to 7d after ICU admission. Correction of the obtained counts for the hydration status did not improve the obtained results. Conclusion Urinary particle analysis with RTEC is useful for the early diagnosis of AKI following cardiac surgery, especially at 12h and 24h after ICU admission.