A urinary tract infection is a common cause of white blood cells appearing in the urine, according to MedicineNet. While white blood cells from the opening of the urethra (in both men and women) or the vagina (in women) sometimes contaminate samples, anomalous levels indicate a noteworthy condition.
Cystitis (bladder infection) or pyelonephritis (kidney infection) are common urinary tract infections that send white blood cells and/or bacteria into the urine. Medical technicians perform microscopic examination of urine for the cells and record the number that appear, as stated by MedicineNet. Women are prone to develop cystitis and urethritis (infection of the urethra) more frequently than men because of the shorter distance from the urethra to the anus in the female anatomy.
In addition to white blood cells, epithelial and red blood cells occasionally appear in urine samples as well. If epithelial cells appear, a likely cause is inflammation at some point in the bladder; however, epithelial cells also come from the skin sometimes and may be the result of a contaminated sample. Red blood cells sometimes enter the urine as a result of trauma in the catheterization process or from the vagina as a part of menstruation. Elevated red blood cell counts in urine are possible signs of trauma, tumors, infection or kidney stones. If the red blood cells show signs of distortion, kidney inflammation is a possible cause, reports MedicineNet.