- Chronic kidney disease: according to the K-DOQI guidelines ( kidney damage ≥ three months, as defined by structural or functional abnormalities of the kidney, with or without decreased GFR, manifest by either: pathological abnormalities; or markers of kidney damage, including damage in the composition of blood or urine test, or abnormalities in imaging tests; GFR< 60 ml/min/1.73m² for ≥ three months, with or without kidney damage)