An abnormally high white blood cell count in the urine indicates inflammation of the kidneys or urinary tract, states the American Association for Clinical Chemistry. The most common cause of a high number of WBCs in the urine is a bladder or kidney infection.
White blood cells help the body fight infection by identifying and destroying foreign invaders, explains the University of Rochester Medical Center. When part of the body is being attacked with bacteria, viruses or other organisms, white blood cells travel to that area of the body to fight the infection. If a person has a urinary tract infection, white blood cells rush to the bladder to get the infection under control, increasing the number of WBCs in the urine.
Someone with interstitial cystitis may also have an increased number of white blood cells in the urine, states WebMD. Interstitial cystitis is inflammation of the bladder that is not caused by an infection. As of February 2015, scientists do not know exactly what causes interstitial cystitis. Some researchers believe it is the result of a defect in the lining of the bladder. Interstitial cystitis may also be caused by an overactive immune system, overproduction of histamine or changes to the nerves that supply the bladder.