Chronic kidney disease (CKD) refers to abnormalities of kidney structure or function, that are present for 3 months or more. It may be caused by several conditions – such as diabetes, high blood pressure or congenital conditions. Identifying the underlying cause of CKD is integral to its treatment and management.
The kidneys essentially ‘clean’ the blood by filtering it through millions of tiny functional units called nephrons (Lote 2012). When the kidneys are healthy, they filter about half a cup of blood each minute and produce around 1.5 litres of urine a day. Urine contains waste products and toxins, which the kidneys remove from the blood. The kidneys also help to maintain a proper balance of salts and minerals in the body, regulate blood pressure, absorb glucose and activate vitamin D.
CKD is a common and costly disease; however, it is largely preventable as a number of its key risk factors are modifiable. The number of people with CKD in Australia is increasing (AIHW 2018), and prevalence rates are likely vastly underestimated (ABS 2013).
Because the kidneys can continue to work even when they are damaged, most people do not realise they have CKD until the disease has progressed far enough for symptoms to develop.
Kidney failure describes the point at which a kidney transplant or dialysis is required for a person to survive. Clinically, it is defined by an estimated glomerular filtration rate (eGFR) of less than 15 mL/min/1.73m2, or being on dialysis. Treatment and management of kidney failure place a significant burden on the person, their carers, families and friends and the health system.
Fortunately, simple tests performed by a general practitioner can identify most cases of CKD when the disease is in its early stages, enabling treatment to prevent or slow progression and reduce the likelihood of developing kidney failure.
In 2020, Kidney Disease: Improving Global Outcomes (KDIGO) released new guidelines for nomenclature (naming) related to kidney function and disease (Levey et al. 2020). This report uses updated terminology based on these guidelines.
What is kidney disease?
Kidney disease can be acute (lasting less than 3 months) or chronic (lasting 3 months or more).
Chronic kidney disease
Clinically, chronic kidney disease (CKD) is defined as one of the following being present for 3 months or more:
- estimated or measured glomerular filtration rate (eGFR/GFR) of less than 60mL/min/1.73m2, with or without evidence of kidney damage.
- kidney damage with or without decreased GFR, indicated by any of the following:
- albuminuria – a condition caused when the kidneys cannot filter large protein molecules out of the blood, so they pass into the urine
- haematuria – the presence of blood in the urine, not caused by another condition
- structural abnormalities, for example abnormally small kidneys
- pathological abnormalities, for example interstitial nephritis (inflammation of part of the kidneys).
CKD is classified into 5 stages, depending on the level of kidney function.
Stages 1 and 2
eGFR ≥ 60, with albuminuria, haematuria, or a pathological or structural abnormality
There are usually no symptoms, as the kidneys are still able to function adequately when they are slightly damaged. This makes diagnosis difficult. The eGFR is normal (≥90mL/min/m2; stage 1) or slightly reduced (between 60 and 89 mL/min/m2; stage 2). The risk of disease progression depends on albuminuria levels.
Stages 3 and 4
eGFR between 15 and 59, with or without albuminuria
The level of waste (urea and creatinine) in the blood rises and a person may start to feel unwell. Kidney function is reduced and blood pressure rises. This is usually when diagnosis occurs. Stage 3 is marked by a moderate reduction in eGFR (between 30 and 59 mL/min/m2) and is divided into stage 3a and 3b. Stage 4 is marked by a severe reduction in eGFR (between 15 and 29 mL/min/m2). In these stages, the risk of progression can depend on both GFR and albuminuria stages.
Stage 5 – kidney failure (also known as end-stage kidney disease)
eGFR < 15 or on dialysis
This is marked by substantial loss of kidney function. The kidneys are no longer able to adequately filter waste from the blood and the person requires kidney replacement therapy – either dialysis or a kidney transplant – to stay alive. The risk of progression is very high.
Acute kidney injury
Acute kidney injury (AKI) refers to a sudden decline in GFR due to a rapid increase in serum creatinine or oliguria (a decrease in urine output) or both (KDIGO AKI Work Group 2012). It has multiple causes, including illness, medications, and injuries to the kidney. Following AKI, kidney function often returns to normal within 3 months.
Source: KHA 2020a, b, c.
Purpose and structure of this report
CKD is a growing concern in Australia. This online report provides policy-makers, health professionals, researchers and the broader community with a comprehensive summary of the latest available data on CKD in the Australian population, including breakdowns by remoteness area, socioeconomic area and Aboriginal and Torres Strait Islander status.
It focuses on:
- CKD prevalence (existing cases) and incidence (new cases) of kidney failure estimates
- risk factors for CKD
- common comorbidities
- treatment and management
- morbidity and mortality estimates
- impact in terms of burden of disease, expenditure and deaths.
Need more information?
Please note: the information in this report does not contain medical advice. If you are concerned about your health, consult a qualified health care professional for guidance on your personal medical needs.
For further information on CKD education and support programs, see the Kidney Health Australia website or the Healthdirect website.