Improved Classification of Urinary Tract Infection: Future Considerations Vitaly Smelov a,b, *, Kurt Naber c , Truls E. Bjerklund Johansen d a Screening Group, International Agency for Research on Cancer, World Health Organization, Lyon, France; b Department of Urology and Andrology, North-Western State Medical University named after I.I. Mechnikov, St. Petersburg, Russia; c School of Medicine, Technical University of Munich, Munich, Germany; d Department of Urology, Oslo University Hospital, Oslo, Norway 1. Introduction Urinary tract infections (UTIs) are among the most frequent bacterial infectious diseases imposing a substantial finan- cial burden on the society [1]. UTIs account for nearly 7 million office visits and 1 million emergency department visits, resulting in 100 000 hospitalizations in the United States each year [2]. It is the 15th most common condition seen by family physicians and is the diagnosis code for 2% of family medicine visits [3]. UTIs are more common in women than in men. In the United States, nearly one in three women will have had at E U R O P E A N U R O L O G Y S U P P L E M E N T S 1 5 ( 2 0 1 6 ) 7 1 – 8 0 ava ilable at www.sciencedirect.com journa l homepage: www.europea nurology.com Article info Keywords: Antibacterial treatment of urinary tract infections Antibiotic resistance Classification of urinary tract infections European Section of Infection in Urology Metagenomic sequencing Microbiome Microbiota Urinary tract infections Abstract The current European Association of Urology and European Section of Infection in Urology classification of urinary tract infections (UTIs) is a working instrument useful for daily patient assessment and clinical research. This new classification of UTI is based on clinical presentation, risk factors, and severity scale. Symptomatic UTIs are classified as cystitis, pyelonephritis, and urosepsis, considering that the urosepsis syndrome is the most severe form and that pyelonephritis is more severe than cystitis. The risk factors are phenotyped according to the ORENUC system: O indicates no known risk factors; R, risk of recurrent UTIs but without risk of a more severe outcome; E, extraurogenital risk factors; N, relevant nephropathic diseases; U, urologic resolvable (transient) risk factors; C, permanent external urinary catheter and unresolved urologic risk factors. Although clinical findings, culture tests, and microscopy remain the standard methods for diagnosing UTIs, improved detection of bacteria by novel diagnostic technologies, such as metagenomic sequencing (MGS), might change this paradigm in the future. Applying a culture-independent MGS technology allows detection of rich bacterial communities in urologic patients with ‘‘sterile’’ urine. However, the clinical relevance of detecting difficult-to-culture bacteria needs to be established by well-designed clinical studies. Patient summary: The current European Association of Urology Section of Infec- tion in Urology classification of urinary tract infections (UTIs) is useful for patient assessment. Symptomatology and urine culture remain the standards for diagnos- ing UTIs. Novel technologies will further explore the interactions between the host and microorganisms in the urogenital tract. # 2016 European Association of Urology. Published by Elsevier B.V. All rights reserved. * Corresponding author. Screening Group, International Agency for Research on Cancer, World Health Organization, 150 cours Albert Thomas, Lyon, 69372, France. E-mail address: vitsmelov@yahoo.com (V. Smelov). http://dx.doi.org/10.1016/j.eursup.2016.04.002 1569-9056/# 2016 European Association of Urology. Published by Elsevier B.V. All rights reserved.