Acute kidney injury after liver surgery: does postoperative urine output correlate with postoperative serum creatinine?

Background: Acute kidney injury (AKI) after hepatectomy occurs in around 10% of cases. AKI is often defined based only on postoperative serum creatinine increase. This study aimed to assess if post-operative urine output (UO) correlated with serum creatinine after hepatectomy. Methods: All consecutive hepatectomy patients (2010-2016) were assessed. AKI was defined according to KDIGO criteria: serum creatinine increase >= 26.5 mu mol/l, creatinine increase >= 1.5x baseline creatinine, or postoperative oliguria. Oliguria was defined as daily mean UO <0.5 mL/kg/h. AKI was subdivided into creatinine-based or oliguria-based AKI according to the defining criterion. Results: Out of 285 patients, AKI was observed in 79 cases (28%). Creatinine-based AKI occurred in 25 patients (9%) and oliguria-based only AKI in 54 patients (19%). Ten patients fulfilled both criteria (4%). Postoperative UO correlated poorly with postoperative serum creatinine level in both whole cohort (rho = -0.34, p <0.001) and AKI subgroup (rho = -0.189, p = 0.124). No association was found between postoperative oliguria and postoperative serum creatinine increase (HR = 0.5, 95%CI: 0.2-1.9, p = 0.341). On multivariable analysis, operation duration >360 minutes was the only predictor of creatinine increase (HR = 3.6, 95%CI: 1.1-11.4, p = 0.032). Conclusion: Postoperative UO showed poor correlation with postoperative serum creatinine both in all patients and AKI patients. Surgery duration >360 minutes appeared as the only independent predictor of postoperative serum creatinine increase.