The aim of this retrospective cohort study was to investigate the relationship between intraoperative urine output during major abdominal surgery and the development of the AKI and to identify an optimal threshold for predicting the differential risk of AKI.

Oliguria is widely viewed as an early marker of decreased kidney perfusion and impending acute kidney injury ( AKI) .The use of urine output (UO ) to guide fluid therapy is often recommended by textbooks and guidelines  and is the standard practice in perioperative or critical care settings.

The threshold of intraoperative urine output below which the risk of acute kidney injury (AKI) increases is unclear. Perioperative data were collected retrospectively on 3560 patients undergoing major abdominal surgery (liver, colorectal, gastric, pancreatic, or oesophageal resection) at Kyoto University Hospital.

Researchers evaluated the relationship between intraoperative urine output and the development of postoperative AKI as defined by recent guidelines. This is the first study to attempt to identify an optimal threshold of intraoperative UO associated with a differential risk of AKI.

Logistic regression analysis was performed to adjust for the patient and operative variables, and the minimum  P -value approach was used to determine the threshold of intraoperative urine output that independently altered the risk of AKI.

The overall incidence of AKI in the study population was 6.3% . Using the minimum  P -value approach, a threshold of 0.3 ml kg -1  h -1 was identified, below which there was an increased risk of AKI (adjusted odds ratio, 2.65; 95% confidence interval, 1.77-3.97;  P <0.001 ).

The addition of oliguria <0.3 ml kg -1h -1  to a model with conventional risk factors significantly improved risk stratification for AKI (net reclassification improvement, 0.159, 95% confidence interval, 0.049-0.270,  P = 0.005).

Previous studies in perioperative settings failed to demonstrate a significant association between intraoperative UO and AKI, and a recent review suggested that intraoperative UO is not related to perioperative renal function.

In Conclusion, Among patients undergoing major abdominal surgery, intraoperative oliguria <0.3 ml kg -1  h -1  was significantly associated with increased risk of postoperative AKI.

Further research is required to determine whether intraoperative management targeting the urine flow rate at ≥0.3 ml kg−1 h−1will reduce the risk of AKI.