Context and Definition
Context
Acute Kidney Injury (AKI) is a sudden decline in kidney function. [1] AKI in children is associated with an increased risk of death and prolonged hospital stay, [2] and increased risk of chronic kidney disease. [3]
Recognition of children at risk in the paediatric emergency department can facilitate the early diagnosis of AKI and help reduce the risk of harm. [1]
This e-learning is based on guidance on AKI from the British Association of Paediatric Nephrology (BAPN) and the National Institute of Clinical Excellence (NICE).
Definition
Acute kidney injury (AKI) is defined as a sudden loss of kidney function, leading to a decrease in glomerular filtration rate (GFR). [1]
It is detected through [4]:
- a decrease in urine output in most cases (< 0.5 ml/kg/hour for 8 hours or more)
- blood testing – an increased serum creatinine (compared to baseline or reference range)
LIMITATIONS OF SERUM CREATININE
Despite its wide use, serum creatinine is a poor marker for AKI; it varies with age, weight and sex. It is also a late and insensitive marker for AKI – levels only rise significantly when 25-50% of renal function is lost. [1] There is also a lack of consensus on definition of AKI, with over 30 definitions in the literature. The definition used by the NHS England AKI algorithm described below is based on the Kidney Disease Improving Global Outcomes (KDIGO) classification. [1]
Standardisation of AKI definition
NHS England has agreed a national algorithm to standardise the definition of AKI, and has recommended that this algorithm is automatically calculated by hospital laboratory systems:
- Serum creatinine is used to create an ‘early warning’ AKI score for severity of AKI (table 1). This score is calculated by comparing the measured creatinine to previous results if available or to a reference upper limit for the child’s age (table 2).
An AKI score should be automatically calculated, and available alongside the creatinine result (table 1)
Stage 1 AKI is often unrecognised and may be the first sign of dehydration or intrinsic renal disease – early detection can reduce progression and harm.
Table 1: Acute Kidney Injury (AKI) Warning Score, based on the NHS England AKI algorithm
| AKI Stage | Measurement |
| Stage 1 | Measured creatinine is more than 1.5 to 2 times either
● previous baseline creatinine result ● or upper reference creatinine limit for age |
| Stage 2 | Measured creatinine is more than 2 to 3 times either
● previous baseline creatinine result ● or upper reference creatinine limit for age |
| Stage 3 | Measured creatinine is more than 3 times either
● previous baseline creatinine result ● or upper reference creatinine limit for age |
Table 2: Paediatric reference ranges for creatinine (Source: UK Paediatric Laboratory Medicine Network)
| Age Group | Male (Creatinine μmol/l) | Female (Creatinine μmol/l) | ||
| Lower Limit | Upper Limit | Lower Limit | Upper Limit | |
| 0 – <14days | 27 | 81 | 27 | 81 |
| 14d – <1yr | 14 | 34 | 14 | 34 |
| 1 – <3yr | 15 | 31 | 15 | 31 |
| 3 – <5yr | 23 | 37 | 23 | 37 |
| 5 – <7yr | 25 | 42 | 25 | 42 |
| 7 – <9yr | 30 | 48 | 30 | 48 |
| 9 – <11yr | 28 | 57 | 28 | 57 |
| 11yr | 36 | 64 | 36 | 64 |
| 12yr | 36 | 67 | 36 | 67 |
| 13yr | 38 | 76 | 38 | 74 |
| 14yr | 40 | 83 | 43 | 75 |
| 15yr | 47 | 98 | 44 | 79 |
| 16yr | 54 | 99 | 48 | 81 |
| >16 yr | Adult Range | Adult Range | ||
| 59 | 104 | 45 | 84 | |