The development of acute pyelonephritis is a frequent cause of death in patients with bladder cancer. Treatment of this category of patients is very difficult because of their severe condition caused by the combination of purulent and cancerous processes, as well as severe impairment of urine passage in the upper urinary tract, which is associated with a long asymptomatic course of bladder cancer and, therefore, late diagnosis of the disease. In most cases, the development of acute pyelonephritis is caused by ureteral obstruction as a result of tumor infiltrating growth, resulting in intramural blockage and retention changes in the upper urinary tract. The causes of inflammatory complications after surgical intervention for bladder cancer are, as a rule, surgical trauma and defect of ureterocystoanastomosis.