Causes of occult blood in urine: 1. Glomerulonephritis or interstitial nephritis can cause the presence of occult blood in urine. 2. Urinary tract infections, such as cystitis and pyelonephritis, can cause urinary occult blood. 3. Stones in the urinary system, like kidney stones, ureteral stones and bladder stones, can lead to the presence of kidney occult blood. 4. Tumors in the urinary system, such as kidney cancer and ureteral cancer, can lead to the presence of urinary occult blood. 5. Finally, urinary occult blood can also be seen in some systemic diseases, such as systemic lupus erythematosus nephritis, allergic purpura nephritis, and thrombocytopenic purpura, etc., which can also lead to the appearance of urinary occult blood.