If the cause is acute prostatitis or urinary system infection, such as cystitis and pyelonephritis, the occult blood in urine is not serious and will disappear after active anti-infection treatment. 2, the common causes of occult blood in urine are urinary stones or kidney cyst rupture and bleeding. After treatment, for example, urinary stones can be treated by stone removal and the occult blood in urine will disappear. The most common nephritis can also cause occult blood in the urine.