Postoperative acute kidney injury (AKI) is linked to an increase in morbidity and mortality, particularly in elderly populations. This study's aim was to assess the accuracy of the Doppler renal resistive index (RI) in detecting AKI at an early stage after hip fracture surgery.

This prospective single-centre study included 48 patients suffering hip fractures requiring surgery and who presented risk factors for the development of AKI. The RI was calculated preoperatively and postoperatively in patients without pain and with haemodynamic and respiratory stability. The occurrence of AKI was determined by measurements of serum creatinine according to AKIN criteria.

Twenty-nine patients (60%) developed AKI during the first five postoperative days, without need for dialysis. The RI was increased in patients who developed postoperative AKI 0.68 (0.67–0.71) vs. 0.72 (0.7–0.73); P=0.014 for the preoperative index; and 0.6 (0.58–0.68) vs. 0.74 (0.71–0.76); P<0.0001 for the postoperative index. A postoperative index superior or equal to 0.706 is a marker for the early detection of AKI with a high sensitivity and a high specificity (76% and 89%, respectively).

The calculation of the RI during the perioperative periods of hip fracture surgery predicts early and effectively the postoperative occurrence of AKI, thus allowing treatment to be anticipated so as to improve patient prognosis.