An 8-year-old girl complains of frequent painful urination in small amounts and urinary incontinence. The signs have been present for 2 days already. She explains her disease by overexposure to cold. Costovertebral angle tenderness is absent. Complete blood count is without pathologies. Urine test: leukocytes – 20-30 in the vision field, erythrocytes – 40-50 in the vision field, unchanged, bacteriuria. What is the most likely diagnosis?