Urinary tract infection – UTI – is a disease in 80 % of cases caused by Escherichia coli. It mostly affects the lower urinary tract, and it may also occur as pyelonephritis, which in turn is a risk factor for acute kidney injury – AKI. The aim of the experiment was to develop an analytical model of the AKI that develops as a result of ascending UTI caused most frequently by the isolated from the urine of patients bacteria - E. coli.For studies of AKI which occurs as a consequence of UTI, female Wistar rats were used. On zero day, group 1, 2 and 3 UTI was induced via urethra infusion of a suspension of bacteria in three different doses of – 105, 107, 109 c.f.u./ml. On the days 0, 7, 14 and 21 of the experiment urine and blood were taken for analysis, in order to assess the renal filtration function. 30 various parameters were analyzed.The studies showed that pyelonephritis develops as a result of induction of UTI by using in the course of experiment, any of the doses of the bacteria E. coli. UTI – inducing dose had an impact on the course of infection and the extent of inflammation of the urinary tract by a simple relationship – the higher the induced dose is, the more rapid is the course of the infection, and the larger the area of the organ involved in the process of inflammation. AKI was diagnosed on the basis of the growth in serum creatinine level and urine disorders, accom ; panied by increased concentrations of markers of AKI – IL-6 and uric acid. The intermediate dose of E. coli – 107 c.f.u/ml was the cause of isolated, renal AKI, whereas dose 109 c.f.u./ml caused AKI as a consequence of UTI ascend, but also bacteremia and urosepsy. On the basis of the results obtained in the experiment, the particular time of the occurrence of the organ defect cannot be specified, because it requires testing based on smaller time intervals.