Acute kidney injury (AKI) is a rapid reduction in kidney function over hours/ days with failure to maintain fluid, electrolyte and acid-base balance. It has a high incidence rate, with 20% of emergency hospital admissions developing AKI, and is associated with significant mortality and morbidity. It is estimated that up to one third of cases have the potential to be prevented. 

AKI is graded stage 1, 2 or 3 depending on severity. AKI is different from chronic kidney disease (CKD) which is a decline in renal function over several months to years. Patients with CKD can still develop an acute kidney injury. Often referred to as AKI on CKD.

AKI is diagnosed by:

• a rise in serum creatinine and/or

• a reduction in urine output

Creatinine is a waste/breakdown product of muscle metabolism that is usually produced at a relatively constant rate and cleared solely by the kidneys. It accumulates in renal dysfunction and as such is used as a marker of renal function. The normal range for creatinine is between 45-120 umol/L - the actual numeric value is dependant upon a number of factors including age, gender, ethnicity and muscle mass. Hence a rise in serum creatinine is calculated from their baseline if known. The baseline creatinine is the lowest creatinine in the last 3 months. The table below shows the different stages of AKI diagnosed by creatinine.

Urine output is another important indicator of kidney function. A reduction in urine output is another way of diagnosing AKI. The table below shows the different stages of AKI diagnosed by reduced urine output.

Causes of AKI

The causes of AKI are grouped into pre-renal, renal (intrinsic) and post renal causes. The majority of AKI is from pre-renal causes, with sepsis being one of the leading causes of AKI. Please click on the diagram below for more information: