The professional term for bleeding in the urine of a 75-year-old man is hematuria, and the causes of hematuria include urinary system diseases, rheumatoid immune diseases and blood system diseases. 1. urinary system diseases: urinary system diseases are the most common causes of hematuria in the elderly, such as glomerulonephritis, kidney stones, IgA nephropathy, and urinary tract infections, tumors and other diseases. These diseases cause abnormal glomerular filtration and reabsorption function by destroying renal tissues, thus leading to hematuria. 2. Rheumatic immune diseases: Rheumatic immune diseases can also cause hematuria, such as systemic lupus erythematosus, dermatomyositis, polyarteritis, systemic sclerosis, and rheumatoid arthritis and other diseases, which can cause hematuria by damaging renal tissues. 3. Blood system diseases: Leukemia, hemophilia, thrombocytopenic purpura, aplastic anemia and other blood system diseases can also cause hematuria by damaging red blood cells and platelets. If you find that the elderly have hematuria symptoms, you need to go to the hospital in time for professional examination and active diagnosis and treatment.