Why is acute kidney injury important?

  • Acute kidney injury (AKI) is a common, serious, costly condition. The incidence of acute kidney injury is rising.
  • Epidemiological analysis has demonstrated a strong association between the development of acute kidney injury and hospital mortality (Reference 1). The development of severe AKI has been shown to be one of the strongest predictors of inpatient death, representing a stronger risk factor than the need for artificial ventilation.
  • A recent analysis has shown that for AKI recorded Nationally through coding on HES (that, due to underrepresentation in coding constitutes only the most severe AKI cases) 28.11% of patients with AKI died before discharge. These patients were 10 times more likely to die during hospitalisation than patients without AKI.
  • A review of more than 80,000 hospital admissions in 3 London hospitals has demonstrated a mortality risk for all AKI - ascertained by analysis of pathology results, not just the most severe forms visible in coding - of 14% in the over 65 age group, this rising to 35% when biological parameters of dehydration are also present (Nangalia et al, under peer review). Kerr et al and other have found similar ‘all AKI’ mortality rates.
  • The number of excess deaths associated with AKI has been estimated at 40,000 per annum for England and therefore 10,000 per annum for London. An NCEPOD enquiry into National AKI deaths, ‘Adding insult to Injury’, reported that around 20% of AKI cases were preventable. As such around 2,000 deaths in London are likely due to preventable AKI. The mortality benefit achievable through enhanced care for all, including non-preventable AKI, may be far higher.
  • London AKI Network data has shown that, of patients requiring acute dialysis for AKI in renal units, 15% are deceased at 3 months while a further 40% require long-term dialysis. As such 480 patients per annum enter long-term dialysis after surviving AKI in London. This is consistent with a National estimate of 1369 long-term dialysis entrants for AKI per annum for England. Both these figures exclude patients with CKD stages 4-5 prior to their AKI episode, so may underestimate the total contribution of AKI to the prevalence of long-term dialysis dependence.
  • A single episode of severe AKI has been shown, through multivariate analysis, to confer an 8-fold risk of developing end-stage kidney disease and a 30 fold risk of developing CKD. This, in turn, confers life-long risk of morbidity, mortality (particularly and progression to dialysis dependence.
  • The healthcare cost incurred through coded episodes for AKI in London was £16M for 2012-2013. A further £750,000 in cost was incurred through the acute dialysis tariff (London Renal Strategic clinical Network analysis).
  • The bulk of the healthcare cost associated with AKI care does not, however, have coding visibility. One reason for this is that AKI episodes are often secondary are not grouped to an AKI HRG. A recently published analysis - commissioned by NHS Kidney Care and utilising pathology data for AKI diagnosis - has shown that the true costs of AKI care are far higher. From this analysis if one assumes a quarter of English AKI to be in London, 208,000 admissions in London have AKI incurring (just for patients not grouped to the AKI HRG LAO7) an additional 0.6M bed days. 40,000 of these bed days are in critical care. Total inpatient expenditure for AKI care in London is therefor estimated to be £250M per annum.
  • The same authors, using a Markov model, estimated subsequent lifetime costs incurred for treatment of patients who have survived acute kidney injury in a single year (2010-2011). The costs for London are estimated at 44.75M for lifelong therapy of a single years AKI cohort. This is based on subsequent costs of CKD and dialysis resulting from the AKI episodes. The lifetime QALY loss was estimated at 1.4 per inpatient with AKI (Reference 3).
  • London AKI Network data suggests 3,000 critical care beds per annum are utilised for patients who have been accepted by renal units but have not transferred. Failure to effectively deliver this specific aspect of the pathway is alone (using NHS reference costs of £1213 per critical care bed day) costing the London health economy £3.6M per annum. A further £7.2M per annum is consumed for single organ renal support in critical care units for patients not yet accepted for transfer but who may be more cost- effectively managed in renal units. Snapshot data has demonstrated that prevalence of renal support in critical care units in London is three times the National average. If this were merely reduced by 50% from a mean of 70 patients per day to 35 patients per day this would result in a cost saving of £15.5M per annum (Appendices 5 and 7).
  • This data collectively suggests that similar health economic benefits are achievable through more robust delivery of the AKI care pathway including prevention, detection, early therapy, escalation and access to tertiary services.