Obesity and recovery from acute kidney injury (Ob AKI): a prospective cohort feasibility study.

Objectives: To test the methodology of recruitment, retention and data completeness in a prospective cohort recruited after a hospitalised episode of acute kidney injury (AKI), to inform a future prospective cohort study examining the effect of obesity on AKI outcomes.

Design: Feasibility study. Setting: Single centre, multi-site UK tertiary hospital. Participants: 101 participants (67M; 34F) with a median age of 64 (IQR 53-73) years, with and without obesity, recruited within 3 months of a hospitalised episode of AKI. Outcome measures: Feasibility outcomes were recruitment (>15% meeting inclusion criteria recruited), participant retention at 6 and 12 months (≥80%) and completeness of data collection. Exploratory measures included recovery from AKI (regaining >75% of pre-AKI estimated glomerular filtration rate [eGFR]) at 6 months, development or progression of chronic kidney disease (CKD) (kidney function decrease of ≥25% +  rise in CKD category) at 12 months, and associations with poorer kidney outcomes.

Results: 41% of eligible patients consented to take part, exceeding the target recruitment uptake rate of 15%. Retention was 86% at 6 months and 78% at 12 months; 10 patients died and three commenced dialysis during the study. Data were 90%-100% complete. Median BMI was 27.9 kg/m2 (range 18.1 kg/m2-54.3 kg/m2). 50% of the cohort had stage 3 AKI and 49% had pre-existing CKD. 46% of the cohort met the AKI recovery definition at 6 months. At 12 months, 20/51 patients developed CKD (39%) and CKD progression occurred in 11/49 patients (22%). Post-AKI interleukin-6 and cystatin-C were associated with 12 months decline in eGFR.

Conclusions: Feasibility to conduct a long-term observational study addressing AKI outcomes associated with obesity was demonstrated. A fully powered prospective cohort study to examine the relationships between obesity and outcomes of AKI is warranted.