Summary. to establish violations of the structural and functional properties of peripheral blood erythrocytes in serous and purulent acute pyelonephritis before and after conventional therapy.
Materials and methods. The structural and functional properties of erythrocytes of 62 patients with various forms of acute pyelonephritis, randomized by age, sex, and the minimum number of concomitant diseases in remission, were examined. Results and its discussion. In serous, to a greater extent, in the purulent form of acute pyelonephritis, violations of the usual ratio of erythrocyte membrane proteins responsible for the flexibility and shaping of the membrane, intracellular metabolism, stabilization and structure formation of the plasma membrane skeleton were established. Disturbances in the lipid content of erythrocyte membranes, which form the basis of the lipid framework of the plasma membrane and play a major role in the ordering of protein macromolecules and normal erythrocyte metabolism, were revealed. Conclusion. In the serous and purulent phases of inflammation, disturbances in the qualitative and quantitative variant of the protein and lipid fractions of the membranes cause functional changes in blood erythrocytes that are not normalized by standard treatment in the purulent form of the disease, which requires the development of correction methods.4
Conclusions: In patients with NDE before treatment, an increase in the level of only one representative of the investigated proteins of the circulating erythrocyte membrane out of 12, namely tropomyosin, was revealed, which can be used in the differential diagnosis of pyelonephritis forms. In patients with a purulent form of pyelonephritis, a more significant increase in lipid peroxidation processes, a weakening of the body’s antioxidant system, and a decrease in the adsorption characteristics of erythrocytes were revealed. Given the lack of effectiveness of basic treatment in relation to most indicators of the structural and functional properties of erythrocytes, it is necessary to include immunomodulatory and antioxidant drugs in the complex treatment for serous and purulent forms of acute pyelonephritis, which will help reduce complications and enhance regenerative processes.
Recommendations: to recommend to medical specialists to use indicators of structural and functional properties of erythrocytes in difficult cases of differential diagnosis of forms of acute pyelonephritis

Keywords: acute serous and purulent pyelonephritis, structural and functional properties of erythrocytes