Classification of Urinary Tract Infections: A Contemporary Guide for Clinical Practice and Research

When the concept of complicated and uncomplicated UTI was developed, new antibiotics were introduced almost every year, and the main objective of the classification was to facilitate the design of research protocols to study the effect of new antibiotics and decide the dosing and duration of treatment. The most widely used classifications of UTI are those developed by the Centre for Disease Control and Prevention in USA (CDC) in 1988 and updated in 2008, IDSA in 1992, and ESCMID in 1993. The new era with increasing antimicrobial resistance and need for antimicrobial stewardship calls for a more differentiated assessment of patients and tailoring of treatment according to the concept of personalized medicine. In an attempt to meet this need, the ORENUC classification was introduced by the European Section of Infections I Urology in 2010. In recognition of the characteristics of risk factors relevant for the three infections cystitis, pyelonephritis, and urosepsis, we organized the risk factors into six groups and proposed the ORENUC system for phenotyping. Today, it is time for an ESIU-ORENUC II classification that includes new findings and insights such as metagenomics and collateral effects of antibiotics, mathematical modeling, artificial intelligence, and modern communication technology to facilitate bedside decision-making.