Radiological procedures require the intravascular administration of iodinated 
contrast media, which are becoming a great source of an iatrogenic disease known 
as contrast-induced nephropathy. The development of contrast-induced nephropathy 
is associated with prolonged hospitalization, the potential need for renal 
replacement therapy, and increased mortality. Despite numerous clinical and 
experimental studies, several important issues regarding contrast-induced 
nephropathy remain controversial. One of the controversial points is its very 
definition: a universally accepted definition of contrast-induced nephropathy 
does not exist. This can be a major problem. Differing definitions of 
contrast-induced nephropathy and the clinical importance of these definitions 
were discussed in this letter.