Incidence and outcomes of acute kidney injury in admitted inpatients: a retrospective observational study

Acute kidney injury (AKI) is highly prevalent during hospital inpatient admissions and is associated with increased length of stay and mortality. This study aimed to outline the incidence, recognition and outcomes of AKI in patients admitted to a tertiary centre.

We conducted a retrospective observational study of adult inpatients admitted to medical and surgical units for more than 24 h from 1 March 2023 to 31 August 2023. The outcomes assessed were the incidence of AKI, coding of AKI and the length of stay and mortality in patients with and without AKI. In patients referred for nephrology consult, the medical record was reviewed for best practice AKI care, including repeat serum creatinine, documentation, medication review, urinalysis, imaging and fluid balance review and charting.

The incidence of AKI was 22.9% in the 12 543 hospital admissions included. In patients with AKI, the majority had stage 1 (77.4%), followed by stage 2 (15.4%) and stage 3 (7.0%). Mortality was higher in patients with AKI, with 7.4% of patients dying during admission compared with 1.0% of patients without AKI (P < 0.001). Patients with AKI had a longer length of stay, with a median of 6.8 days (interquartile range (IQR), 3.5-13.4 days), compared with those without AKI, with a median of 3.5 days (IQR, 2.0-6.4 days, P < 0.001). There was significant under-recognition of AKI, with <50% of those with AKI having a coded diagnosis. Additionally, in patients referred for nephrology consult, only 16.7% had all aspects of AKI care initiated within a day of meeting the definition for AKI.

AKI was present in more than one in five hospital admissions and associated with longer length of stay and mortality. Improving recognition, management and documentation of AKI is an ongoing priority area.