Abstract
This review paper addresses the definition of acute kidney injury and other related nosologic units, criteria of function, and the RIFLE and AKIN classifications. The new clinical unit called subclinical acute kidney injury as well as kidney damage biomarkers are also focused on.
Difficulties related to the examination of the kidney function - together with suggested solutions - are dealt with, e.g. the issue of measuring and estimating glomerular filtration rate (GFR), the issue of comparability and traceability of creatinine, urea, and cystatin C measurements in the serum, the issue of comparability of different estimated GFR values including the use of GFR estimation in intensive care, the issue of baseline serum creatinine, the influence of biological variability on interpretation, and finally, the issue of choosing and measuring the biomarkers of kidney injury.