The presence of white blood cells in urine indicates a medical problem such as an infection in the urinary tract, bladder or kidneys, according to MedicineNet.com. Because urine is a sterile body fluid, there should be no white blood cells in healthy urine.
Trace amounts of white blood cells may be found in healthy urine due to contamination, which comes from the vagina in females or the urethra opening in males. To detect white blood cells in urine, doctors examine the urine through a microscope and count the number of cells. The quantity is then used to draw conclusions about the severity of the infection.