What causes occult blood in urine?

Common causes of hematuria (blood in urine) include: 1. **Urinary tract infections**: Infections caused by bacteria, viruses, or parasites can lead to inflammation of the urinary tract, resulting in an increased number of red blood cells in the urine. 2. **Kidney diseases**: Conditions such as nephritis, kidney stones, or kidney cysts may cause abnormal filtration of red blood cells into the urine. 3. **Urethral or bladder inflammation**: Localized inflammation can lead to the presence of red blood cells in the urine. 4. **Tumors**: Cancers such as bladder cancer or kidney cancer may cause blood to appear in the urine. 5. **Stones**: Kidney or bladder stones can scratch the urinary tract as they move, causing bleeding. 6. **Exercise-induced hematuria**: Occasionally, strenuous exercise can cause temporary hematuria due to damage to the small blood vessels in the kidneys.