Kidney Learning System

About Chronic Kidney Disease

Chronic kidney disease (CKD) is a worldwide public health problem. In the US alone, 20 million adults (1 in 9) have CKD and another 20 million are at increased risk for developing it, and most people are unaware.

The term CKD refers to the five stages of kidney disease – the early stages (stages 1 and 2) as well as kidney failure (stage 5).

There is growing evidence that early detection and appropriate treatment may be effective in:

Most people with CKD do not die of kidney failure – they die of heart disease! And heart disease, which is the cause of 40-50% of the deaths in CKD, occurs as early as stage 3.

CKD Risk Factors

Diabetes is the leading risk factor for CKD followed by high blood pressure. There are other causes as well.

Clinical Factors
Sociodemographic Factors
Diabetes

Hypertension

Autoimmune diseases

Systemic infections

Urinary tract infections

Urinary stones

Lower urinary tract obstruction

Neoplasia

Family history of chronic kidney diseases

Recovery from acute kidney failure

Reduction in kidney mass

Exposure to certain drugs

Low birth weight
Older age

US ethnic minority status: African
American, American Indian, Hispanic,
Asian or Pacific Islander

Exposure to certain chemical and
environmental conditions

Low income/education

All individuals should be assessed for risk factors for CKD upon their initial medical encounter.

Definition and Classification of Chronic Kidney Disease

KDOQI (Kidney Disease Outcomes Quality Initiatives), an effort to improve patient outcomes through the development of clinical practice guidelines, defines CKD according to the presence or absence of markers of kidney damage and the level of kidney function (glomerular filtration rate [GFR]) – irrespective of the type of kidney disease (the specific diagnosis).

Thus, there are two independent criteria for CKD:

GFR is the best overall index of kidney function in health and disease. Normal GFR varies according to age, sex, and body size; in young adults it is approximately 120-130 mL/min/1.73 m 2 and declines with age. GFR can be estimated from prediction equations such as the MDRD Study equation, which is recommended by KDOQI.

MDRD Study equation:

eGFR (mL/min/1.73 m 2) = 186 x (SCr) – 1.154 x (Age) – 0.203 x (0.742 if female) x (1.210 if African – American)

SCr: serum creatinine in mg/dL; age in years

The MDRD Study equation has not been validated in children (age < 18 years), pregnant women, the elderly (age > 70 years), racial or ethnic subgroups other than Caucasians and African Americans, in individuals with normal kidney function who are at increased risk for CKD, or in normal individuals. Despite these limitations, GFR estimates using equations are more accurate than serum creatinine alone.

Among individuals with CKD, the stage is defined based on the level of kidney function using GFR, with the higher CKD stages representing lower GFR levels. According to a recommendation from Kidney Disease Improving Global Outcomes (KDIGO), an initiative to improve global outcomes for kidney disease, all kidney transplant recipients should be considered as having CKD based on kidney damage to their native kidney, presumed damage to the kidney transplant, and the need for life-long care as a result of prior CKD complications and chronic allograft nephropathy. Another recommendation from KDIGO includes an amendment to the CKD classification to use a “T” for all kidney transplant recipients, at any stage, and a “D” for dialysis at stage 5 for people being treated by dialysis. 1

Stage
Description
GFR mL/min/1.73 m2 (Kidney Function)
1
 Kidney damage with normal or ↑ GFR ≥90
2


        T
 Kidney damage with mild ↓ GFR

for Transplant		 60-89
3
 Moderate ↓ GFR 30-59
4
 Severe ↓ GFR 15-29
5

        D
 Kidney failure

for Dialysis		 <15 (or dialysis)

Abbreviations: CVD, cardiovascular disease; D, Dialysis;
GFR, glomerular filtration rate; T, Transplant

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