#2974 Serial multiparametric magnetic resonance imaging in a prospective cohort of patients with acute kidney injury
Authors: Noble Rebecca , Cox Eleanor F , Taal Maarten W , Selby Nicholas , Francis Susan 
Published: May 2024

Abstract

Background and Aims
Recovery from acute kidney injury (AKI) is traditionally measured using serum creatinine but this can often over-estimate the degree of renal recovery. It is known, however, that failure of recovery of serum creatinine 90 days after AKI strongly associates with subsequent long-term reductions in renal function making it an important clinical timepoint. Magnetic resonance imaging (MRI) is an imaging modality with promise to improve the understanding and characterisation of renal pathophysiology. In a single multiparametric MRI (mpMRI) scan, multiple measures can assess renal morphology, tissue microstructure (T1 relaxation time and diffusion-weighted-imaging (DWI)), oxygenation, perfusion and blood flow. We previously published the first study of renal mpMRI at the time of AKI and during follow up, this showed increased total kidney volume (TKV) and T1 as a measure of inflammation/fibrosis at the time of AKI which remained elevated in some participants at 3 and 12 months despite normalisation of serum creatinine. This study aimed to assess the degree of change between 30 and 90 days post AKI, as the first 90 days after AKI appear to be the important in terms of outcomes.

Method
Prospective observational study of 10 participants with AKI of all stages recruited at the time of AKI and followed up with monthly bloods and urine. MRI scans were collected on a Philips Ingenia 3T at day 30-60 and day 90. The 1-hour protocol included: T2-weighted scans for automated segmentation to compute total kidney volume (TKV), as well as T1 & T2 mapping, DWI, ASL and phase contrast MRI for kidney perfusion and blood flow, and TRUST-MRI and BOLD R2* for kidney oxygenation, and MRE for stiffness.

Results
10 participants were scanned at 2 timepoints, (mean day 45 for 1st scan, 95 for 2nd scan). Baseline characteristics are summarised in Table 1 along with key clinical measures in Table 2. 2 participants had CKD at baseline. Despite a range of peak creatinine values and AKI stages the majority of participants serum creatinine normalised to within 20% of baseline by 30 days (v3) (Fig. 1). Fig. 2 shows the TKV for AKI patients across the 2 visits as compared with healthy values. Despite normalisation of biochemistry, 5 participants had enlarged TKV. The predominant AKI aetiology for these patients was sepsis. Across all participants there is little dynamic change between visits. The participant with the small TKV across both visits had pre-existing CKD, as well as the highest peak creatine. The participant did not recover renal function by day 90 (Figs 1(j) and 2).

Conclusion
Despite recovery of biochemistry, at least half of this AKI cohort had abnormal MR measures at that persisted through one and three months after the AKI episode. There is a trend towards larger TKV in patients with AKI due to sepsis, which needs to be explored in a larger cohort. Analysis of more parameters as well as the addition of liquid biomarkers will enrich these preliminary findings.