A 42-year-old woman has been hospitalized with complaints of dull, aching pain in her lower back, more on the right side, and her body temperature sometimes increasing to subfebrile levels. The patient's medical history states that 10 years ago during pregnancy she had a pain attack in her lumbar region on the right and a fever of 39°C. She underwent treatment with antibiotics. In recent years, she was feeling satisfactory. An increase in blood pressure has been observed for the past 5 years. Urinalysis revealed the following: protein 0.66 g/L, leukocytes - 10-15 in sight, erythrocytes 2-3 in sight. What is the most likely diagnosis in this case?