If hematuria occurs again 3 years after kidney cancer surgery, first of all, determine whether it is tumor recurrence, exclude recurrence, and there may be correlation with urinary stones and inflammation of urinary system. 1. Tumor: there may be recurrence of kidney tumor after surgery, which may be manifested as hematuria; in addition, some patients may also have other tumors in the urinary system, such as ureteral cancer, bladder cancer and so on, which may also have hematuria. 2. Urological stones: some patients may have urinary stones, which may scratch the ureter wall and bladder wall in the process of movement, leading to corresponding symptoms. 3. Inflammation of the urinary system: Inflammation leads to mucosal damage, causing capillary rupture, which can also lead to the production of related symptoms. 4. Blood system diseases: some patients may have spontaneous bleeding and abnormal coagulation due to abnormal coagulation function, which may lead to hematuria symptoms. Once hematuria occurs, it is necessary to consult a doctor in time to observe and diagnose the specific physical condition, and then carry out standardized treatment under the guidance of the clinician to avoid delaying the condition.