What is chronic kidney disease? (AIHW)

What are the kidneys and what do they do?

The kidneys are bean-shaped organs, about the size of an adult fist, located in the back, above the waist and below the lower ribs. They continuously filter the bloodstream, clearing waste products and playing a vital role in controlling the body's level of water and various chemicals. They also produce certain essential hormones.

What is chronic kidney disease (CKD)?

CKD refers to all kidney conditions where a person has evidence of kidney damage and/or reduced kidney function, lasting at least 3 months, regardless of the specific diagnosis of disease or condition causing the disease.

Measuring CKD

Kidney function is measured by the glomerular filtration rate (GFR), which is the amount of blood cleared of waste products by the kidneys in one minute. As GFR cannot be measured directly, current practice is to estimate GFR (eGFR) using age, gender and creatinine levels in the blood.

Stages of CKD

CKD is categorised into five stages (1 through 5) according to the level of reduced kidney function and/or evidence of kidney damage, such as blood or protein in the urine (see Box 1). Simple blood and urine tests performed by a general practitioner can identify most cases of CKD when the disease is in its early stages.

An individual can move up and down stages 1 to 4, but once stage 5 is reached, kidney function does not usually improve. Stage 5 is also known as end-stage kidney disease.

Box 1: Stages of chronic kidney disease

Stage 1: Kidney damage (GFR at least 90 mL/min/1.73 m²)

Evidence of kidney damage but without decreased GFR. Usually no symptoms.

Stage 2: Kidney damage (GFR 60 to 89 mL/min/1.73 m²)

Evidence of kidney damage with some reduction in GFR. Most patients have no symptoms.

Stage 3: GFR 30 to 59 mL/min/1.73 m²*

GFR significantly reduced. May show signs of kidney damage and often indications of dysfunction in other organs. Often there are no symptoms, despite kidney function reduced by up to 70%.

Stage 4: GFR 15 to 29 mL/min/1.73 m²*

Kidney function significantly reduced. Blood levels of urea and creatinine increase, and greater evidence of dysfunction in other organs. Usually only mild symptoms.

Stage 5: End Stage Kidney Disease (ESKD) GFR less than 15 mL/min/1.73 m²*

Range of symptoms and laboratory abnormalities in several organ systems, collectively referred to as uraemia. Kidney replacement therapy (dialysis or transplant) is required when kidney function is no longer sufficient to sustain life, typically at a GFR of around 7–8mL/min/1.73m2.

Source: Kidney Health Australia 2007.

What causes CKD?

CKD shares several risk factors with other chronic diseases such as cardiovascular disease and diabetes, many of them modifiable.

Fixed	Behavioural	Biomedical
Family history and genetics	Tobacco smoking	Diabetes
Increasing age	Physical inactivity	High blood pressure
Previous kidney disease or injury	Poor nutrition	Cardiovascular disease
Low birth weight		Overweight and obesity
Male sex		Systemic kidney inflammation

Treating CKD

The treatment and management of all stages of CKD involves addressing the underlying causes and contributing factors to slow or stop the progression of the disease. This may include taking medications, avoiding substances that are toxic to the kidneys, and/or making lifestyle changes to control risk factors. Other medications may also be required to manage the complications of the disease and replace lost kidney function.

What is chronic kidney disease?

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