Occult blood in male urine may be caused by nephritis, bladder cancer, urinary stones and so on. 1. Nephritis: such as pyelonephritis, glomerulonephritis, etc. Due to bacterial infection of renal pelvis and glomerulus, which leads to inflammatory reaction of renal pelvis and glomerulus, the bacteria will damage the blood vessels of the local tissues and cause blood vessels to rupture and bleed, which will be discharged with the urine, resulting in occult blood in urine. 2. Bladder cancer: when ischemic necrosis occurs in bladder cancer tumor tissues or invades the blood vessels of bladder mucosa, it can cause bleeding, which will be discharged with urine and manifested as occult blood in urine. 3. Urolithiasis: after the occurrence of urinary stones in men, the stones will damage the local mucous membrane, which will cause rupture of capillaries under the mucous membrane, bleeding, and occult blood in urine when the blood is discharged with urine. There are many reasons for men to have occult blood in the urine, including cystitis, renal tuberculosis, etc. Patients should go to the hospital in time, complete the examination, and give treatment under the guidance of the doctor after clarifying the cause of the disease.