A 54-year-old male patient complains of aching pain in the lumbar region, that is getting worse after standing in an upright position, physical exercise, supercooling. The patient also reports of experiencing weakness in the afternoon. Pain in the lumbar region, said about 10 years old. Objectively: pale skin, to- 37, 2°C, AP- 180/100 mm Hg, minor costovertebral angle tenderness (Pasternatsky symptom). In blood: RBCs - 3,5 × 1012/l, WBCs - 6, 5 × 109/l, ESR -22 mm/h. In urine: the relative density -1010, leukocytes -12-15 in the field of vision, erythrocytes - 2-3 in the field of vision. Urine bacterial count - 100000 in 1 ml. What is the most likely diagnosis?