The definition and classification of chronic kidney disease (CKD) have evolved over
time, but current international guidelines define this condition as decreased kidney
function shown by glomerular filtration rate (GFR) of less than 60 mL/min per 1·73
m(2), or markers of kidney damage, or both, of at least 3 months duration, regardless
of the underlying cause. Diabetes and hypertension are the main causes of CKD in all
high-income and middle-income countries, and also in many low-income countries. Incidence,
prevalence, and progression of CKD also vary within countries by ethnicity and social
determinants of health, possibly through epigenetic influence. Many people are asymptomatic
or have non-specific symptoms such as lethargy, itch, or loss of appetite. Diagnosis
is commonly made after chance findings from screening tests (urinary dipstick or blood
tests), or when symptoms become severe. The best available indicator of overall kidney
function is GFR, which is measured either via exogenous markers (eg, DTPA, iohexol),
or estimated using equations. Presence of proteinuria is associated with increased
risk of progression of CKD and death. Kidney biopsy samples can show definitive evidence
of CKD, through common changes such as glomerular sclerosis, tubular atrophy, and
interstitial fibrosis. Complications include anaemia due to reduced production of
erythropoietin by the kidney; reduced red blood cell survival and iron deficiency;
and mineral bone disease caused by disturbed vitamin D, calcium, and phosphate metabolism.
People with CKD are five to ten times more likely to die prematurely than they are
to progress to end stage kidney disease. This increased risk of death rises exponentially
as kidney function worsens and is largely attributable to death from cardiovascular
disease, although cancer incidence and mortality are also increased. Health-related
quality of life is substantially lower for people with CKD than for the general population,
and falls as GFR declines. Interventions targeting specific symptoms, or aimed at
supporting educational or lifestyle considerations, make a positive difference to
people living with CKD. Inequity in access to services for this disease disproportionally
affects disadvantaged populations, and health service provision to incentivise early
intervention over provision of care only for advanced CKD is still evolving in many
countries.