The Epidemiology of Hospitalised Acute Kidney Injury Not Requiring Dialysis in England From 1998 to 2013

Retrospective Analysis of Hospital Episode Statistics

N. V. Kolhe; A. W. Muirhead; S. R. Wilkes; R. J. Fluck; M. W. Taal


Int J Clin Pract. 2016;70(4):330-339. 

In This Article

Abstract and Introduction


Aims: Epidemiology studies of acute kidney injury (AKI) have focused on cases requiring dialysis but those not requiring dialysis represent the majority. To address this gap, we interrogated hospital episode statistics (HES) to investigate population trends in temporal epidemiology of AKI not requiring dialysis between 1998 and 2013.

Methodology: In this retrospective observational study of HES data covering the entire English National Health Service, we identified 1,136,167 AKI events, not requiring dialysis, diagnosed between 1998 and 2013. We explored the effect of age, gender, ethnicity, Charlson's comorbidity score (CCS), method of admission, diagnosis period and AKI in diagnosis codes on temporal changes in the incidence and case-fatality of AKI with specific examination of its predictors.

Result: The incidence of AKI increased from 15,463 cases (317 pmp) in 1998–1999 to 213,700 cases (3995 pmp) in 2012–2013. There was increase in proportion of people over 75 years from 51.1% in 1998–1999 to 63.4% in 2012–2013. Overall unadjusted case-fatality decreased from 42.3% in 1998–2003 to 27.1% in 2008–2013, p < 0.001. Compared with 1998–2003, the multivariable adjusted odds ratio for death was 0.64 in 2003–2008 (95% CI 0.63–0.65) and 0.35 in 2008–2013 (95% CI 0.34–0.35). Odds for death were higher for patients over 85 years (2.93; 95% CI 2.89–2.97), CCS of more than five (2.75; 95% CI 2.71–2.79), emergency admissions (2.14; 95% CI 2.09–2.18) and AKI in the secondary diagnosis code (1.35; 95% CI 1.33–1.36) and AKI in other diagnoses codes (2.17; 95% CI 2.15–2.20).

Conclusions: In England, the incidence of AKI not requiring dialysis has increased and case-fatality has decreased over last 15 years. Efforts to reduce the incidence of AKI and improve survival should focus on elderly people, emergency admissions and those with multi-morbidity.


The International Society of Nephrology (ISN) has recognised acute kidney injury (AKI) as an important cause of death worldwide and has launched a campaign to eradicate preventable death because of AKI in developing countries by 2025.[1] Nevertheless, previous studies indicate that the incidence of AKI is also increasing in developed countries and remains a significant challenge.[2–4] To this effect, National Health Service (NHS) in England has launched Acute Kidney Injury Programme, with a primary aim to reduce the risk and burden of AKI.[5] It is therefore important to gain a more comprehensive understanding of the epidemiology AKI in all countries to inform strategies to reduce incidence and improve outcomes. Information on AKI and its associated case-fatality in populations from different regions of the world is fragmentary and quite often, inconsistent.[6] Moreover, there are no epidemiological studies, other than from USA, describing the temporal epidemiology of AKI.[3,4] Previous published studies in developed countries lack population coverage as they are based on selected samples of hospital patients reported in billing or administrative databases or located in selected clinical locations. Also, epidemiological studies tend to focus primarily on dialysis requiring AKI.[7–9] In recent years, there has been a paradigm shift in understanding of the effect of a relatively small rise in creatinine, which has led to the introduction of a standardised definition and classification of AKI.[10] Despite this, no study has examined national trends in the incidence and case-fatality of AKI after the introduction of RIFLE and the Acute Kidney Injury Network (AKIN) classification and staging system for AKI.[11,12] A crucial feature of the healthcare system in England is that it is universal, funded from taxation and has a national database of all hospital admissions, which gives an opportunity to compare and study populations of different demographic composition.[13] We have recently investigated the epidemiology of AKI severe enough to require dialysis using Hospital Episode Statistics (HES) dataset in England.[14] To address the gap in the literature regarding AKI not severe enough to require dialysis, we combined a national database of all hospital discharges with national census data to investigate population trends and the associated case-fatality as well as their determinants in England between 1998 and 2013.