The publication is devoted to modern approaches to the diagnosis and treatment of complicated and uncomplicated infections of the upper urinary tract (acute and chronic pyelonephritis). Complications, outcomes of these diseases, methods of drainage of the upper and lower urinary tract depending on the cause of urodynamics, stage and form of acute pyelonephritis are considered. Presented is an algorithm for purulent pyelonephritis diagnostics, developed on the basis of diagnostic errors analysis and own clinical observations, allowing to carry out a differentiated approach to choosing a treatment strategy for this disease. The goals and objectives are outlined, the principles of antibacterial therapy are highlighted, the classifications of antibacterial drugs are presented, the features of antibacterial therapy in urology and pregnant women are disclosed. Approaches to the use of empirical antibacterial therapy are justified depending on the route of penetration of infection into the kidney, the form and stage of pyelonephritis. Errors in the diagnosis and treatment of acute pyelonephritis were analyzed.