Chronic kidney disease (CKD) is the general name for heterogenic diseases which affect the structure and function of the kidney and cause permanent and irreversible damage. The definition is based on the presence of kidney damage or a reduced kidney function. A permanent decline in the glomerular, tubular and endocrine functions of both kidneys causes irreversible losses in the nephrons.
According to the guidelines of the Kidney Disease Outcome Quality Initiative (KDOQI), chronic kidney diseases are defined according to the following criteria:
1. Kidney damage present for ≥ 3 months, defined by structural and functional anomalies, with or without restrictions of the GFR, which is manifested in
a. Pathological anomalies or
b. Markers of kidney damage, including anomalies in the composition of the blood or urine, or anomalies in imaging processes
2. A GFR < 60 ml/min/1.73 m2 for three months, with or without kidney damage