Epidemiology of severe purulent pyelonephritis: narrative review

Severe purulent pyelonephritis (SPP) does not have a single international definition, and foreign authors is more often consider it as a part of severe phenotypes of acute pyelonephritis, complicated urinary tract infections, renal abscesses, emphysematous pyelonephritis and urosepsis. Аim: to summarize current data on epidemiology of SPP and related severe phenotypes of complicated pyelonephritis; to identify key demographic and clinical features, risk factors, pathogenetic mechanisms, microbiological trends, outcomes, and directions for further studies. The review analyzes clinical guidelines, population-based studies, systematic reviews, and meta-analyses. According to Global Burden of Disease studies, more than 404.6 million cases of urinary tract infections and related fatal outcomes were reported (236.8 thousand and 5.2 million years of healthy life lost adjusted for disability) in 2019; in 2021, standardized morbidity was 5531.88 per 100000. Population-based studies of acute pyelonephritis demonstrate marked heterogeneity: from 4.2 cases per 10000 person years (according to the Spanish Primary Care Network) to 39.1 cases per 10000 (Korea). Given this epidemiological heterogeneity, identification of risk groups is of practical importance. Elderly age, pregnancy, diabetes mellitus, obesity, urinary tract obstruction, urolithiasis, catheterization, immunosuppression, and antibiotic-resistant pathogens are main risk factors for severe course. For example, emphysematous pyelonephritis is accompanied by high mortality, and catheterization is associated with a daily increase in bacteriuria by 3-8%. The review highlights a need for local SPP registries and adaptation of treatment algorithms to regional resistance data. KEYWORDS: severe purulent pyelonephritis, acute pyelonephritis, complicated urinary tract infections, urosepsis, kidney abscess, emphysematous pyelonephritis, antibiotic resistance. FOR CITATION: Pavlov V.N., Vorobyov V.A., Ananiev V.A. Epidemiology of severe purulent pyelonephritis: narrative review. Russian Medical Inquiry. 2026;10(4):227–234 (in Russ.). DOI: 10.32364/2587-6821-2026-10-4-9