Trends in Hospital Admissions Associated with an Acute Kidney Injury in England 1998–2020: a Repeated Cross-Sectional Study

A rapid rise in diagnosis of acute kidney injury (AKI) has been observed in the UK and worldwide. It is unclear whether this reflects true growth in incidence or improved detection. To investigate this, aggregate data from Hospital Episode Statistics database on all admissions to National Health Service (NHS) hospitals in England 1998/1999 to 2019/2020 were used to extract the number of AKI diagnoses in different age groups and compare them to diseases of similar incidence (pneumonia, heart failure, dementia) based on ICD-10 coding. Haemofiltration procedures were used as proxy for acute kidney replacement therapy (KRT) in a critical care setting. Temporal trends in usage of AKI-specific ICD-10 codes were examined. A total of 356 million inpatient episodes of care over 22 years were analysed. Between 1998/1999 and 2019/2020, primary AKI diagnoses increased from 1.2 to 5.3 per thousand finished consultant episodes. From 2012/2013, when first recorded, secondary diagnoses doubled from 22.8 to 43.2 per thousand finished consultant episodes. The rate of growth in AKI was significantly greater than that of dementia, but not pneumonia or heart failure. The proportion of acute KRT procedures to total AKI diagnoses decreased. This could suggest that the substantial increase in AKI cases observed within NHS in the last two decades is a result of improved detection and coding, particularly of mild cases. In 2019/2020, 96% of AKI cases were encoded as N17.9 ( Acute renal failure, unspecified ), despite 11 other codes being available. We believe that adoption of clinically orientated coding could facilitate further improvements in detection with benefits for clinical practice and research.