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Acute kidney injury (AKI) affects up to 15% of hospitalised patients and commonly arises following severe infections, major surgeries, or exposure to nephrotoxic agents. AKI diagnosis based on changes in serum creatinine levels lacks specificity and may delay diagnosis. MicroRNAs (miRNAs) are short, non-coding RNA oligonucleotides secreted by all cell types. This systematic review evaluated studies investigating miRNAs in AKI to assess their potential as diagnostic markers. Data were included from patients diagnosed with AKI related to sepsis, cardiopulmonary bypass surgery, nephrotoxins, ischemia, radiocontrast exposure, shock, and trauma. Seventy-one studies were included in the review, with the majority focused on sepsis-induced AKI, followed by AKI due to cardiac surgery, ICU admission, and exposure to nephrotoxic agents or ischemic conditions. Studies that employed untargeted assays identified 856 differentially expressed miRNAs, although none were validated across more than one study. Additionally, 68 studies used a targeted approach, measuring miRNAs by qRT-PCR, and reported downregulation of miR-495–3p and miR-370–3p in sepsis-induced AKI after diagnosis. Upregulation of miR-21 at the time of AKI diagnosis was reported in three studies, with a significant pooled effect size of 0.56. Whilst miR-21 levels were also measured 19–24 hours post-cardiac surgery in three studies, the pooled effect was not significant. Despite extensive research into miRNAs in AKI, a significant knowledge gap remains regarding their applicability as diagnostic biomarkers in human AKI.Abstract BS09 Figure 1PRISMA flow diagramAbstract BS09 Figure 2Differentially expressed miRNAs across studies—(A) Standardised mean differences of miR-370–3- and miR-494–3p post-diagnosis in serum, plasma, and urine between controls and patients with AKI. (B,C) Forest plots for miR-21 across studies at the time of AKI diagnosis (B) and 19 or 24 h after cardiac surgery (C). (D) Standardised mean differences of miR-21 in urine, plasma, or serum in patients after cardiac surgery, receiving nephrotoxic agents, or with sepsis