Adverse outcomes associated with both diagnosed and undiagnosed acute kidney injury

Background Acute kidney injury (AKI) is common among hospitalised patients, yet its diagnosis and documentation are inconsistent. Administrative codes show limited sensitivity for diagnosing AKI compared to biochemical criteria. Thus, AKI is often missed or poorly communicated, and the impact of under‐recognised AKI is inadequately understood. Aims This study aimed to identify factors influencing the diagnosis, documentation and coding of AKI and examine outcomes among survivors, including those with undiagnosed AKI. Methods This was a single‐centre retrospective cohort study, reviewing medical records and funding codes for inpatients admitted between 1 July and 28 July 2016. AKI diagnosis and staging were determined using the KDIGO 2012 criteria. Outcomes, including readmissions and mortality rates, were examined up to 12 months after admission. Results Of the 1194 patients who participated, 263 (22.0%) experienced AKI. Among those with AKI, 50.6% had documentation, 39.9% had coding for administrative funding and only 29.0% had the diagnosis noted in the discharge summary. Accurate documentation of AKI was associated with pre‐existing chronic kidney disease (odds ratio (OR): 15.8, 95% CI: 6.0–41.9, P < 0.001) and Stage 2 (OR 3.0, 95% CI: 1.2–7.3, P = 0.017) or Stage 3 AKI (OR 22.9, 95% CI: 2.9–181, P = 0.03). Readmission or death after discharge was higher in patients with AKI than in those without (hazard ratio (HR): 2.2, P < 0.001 and HR: 4.7, P < 0.001 respectively). However, risks were similar in those with documented versus undocumented AKI (HR: 1.2, P = 0.20 and HR: 1.2, P = 0.58 respectively). Only 9.1% (95% CI: 5.9%–13%) of inpatients with AKI received nephrologist care, and 5.3% were referred for outpatient nephrology follow‐up. Conclusions This study highlights the under‐recognition and under‐coding of AKI. Importantly, adverse outcomes were observed regardless of whether AKI was documented, underscoring the need for improved diagnosis, communication and follow‐up.