Critical review of current definitions of urinary tract infections and proposal of an EAU/ESIU classification system

Classification of urinary tract infections (UTI) is important for clinical decisions, research, quality measurement and teaching. Current definitions of UTI are above all based on the concept of the two main categories, complicated and uncomplicated UTI. The category "complicated UTI" especially is very heterogeneous and not always clear. We propose the EAU/ESIU classification system ORENUC based on the clinical presentation of the UTI, categorisation of risk factors and availability of appropriate antimicrobial therapy, which finally may result in the definition of UTI severity groups.