Urinary tract infections (UTI) are amongst the most frequent bacterial infections and therefore are responsible for a significant fraction of antibiotic use, thus carrying a relevant social and economic burden. UTI may present as benign, uncomplicated cystitis or severe, life-threatening urosepsis. Due to the heterogeneity of UTI the European Section of Infections in Urology (ESIU) has introduced a phenotypical classification, based upon the clinical presentation, the risk factors and the antibiotic susceptibility of the causative pathogens. Presence of risk factors is a key point and could change dramatically the course of UTI. In scenario of uroseptic patients, early diagnosis and therapy are mandatory and a successful decompression of the obstructed urinary tract is predictor of survival. The multidisciplinary approach and a timely microbiological characterization are critical in this context.