White blood cells, or WBCs, are not normally found in the urinary tract. Urine is normally sterile and contains no blood cells, so the presence of WBCs in a urine sample indicates inflammation or infection within the urinary tract or kidney. The kidney, bladder and urethra, the tube that leads from the bladder to the kidneys, can all become inflamed or infected.
Cystitis
Cystitis, a bladder infection, is a very common cause of WBCs in urine; bacteria enter the urethra and travel up to the bladder. Cystitis is more common in young boys than girls, although women are more prone to cystitis in adulthood than men. In men, infection may start in the prostate and move up into the bladder to cause cystitis. Symptoms of cystitis include urinary frequency, bladder spasms, a sense of needing to urinate every few minutes and pain just above the pubic bone. Antibiotics are used to treat cystitis.
Interstitial Cystitis
Interstitial cystitis, or IC, is different than cystitis as there's no bacteria present in interstitial cystitis. Instead, the WBCs in the urine come from inflammation of the bladder wall. IC is much more common in women than men and causes urinary urgency, frequency and pelvic pain, according to the Merck Manual. Antibiotics won't help with IC, because no bacteria is present in the urine; dilating the bladder or instilling medications to reduce spasms may help in some cases.
Pyelonephritis
Pyelonephritis, or infection of the kidney, is usually a more severe disease than cystitis. WBCs in the urine in pyelonephritis indicates bacterial infection. People with pyelonephritis can have severe pain, fever, malaise, nausea and vomiting. Some have cystitis symptoms in addition to symptoms of pyelonephritis. Women develop pyelonephritis more often than men; the infection usually spreads upward from the bladder. Pyelonephritis is treated with antibiotics.
Kidney Stones
Kidney stones can lead to cystitis by blocking the passage of urine down the urethra; urine stagnates and is more prone to bacterial infection if stones are present. Irritation of the urethra from the stone may also cause WBCs in the urine. Stones cause severe pain that may come in waves. Sometimes the pain is described as "colicky"; it's hard to sit still when you have a kidney stone. If the stone is blocking the urethra, it may be difficult to urinate or you may urinate only small amounts at a time. Bladder spasms and pain during urination may also occur. People who have had one kidney stone are more likely to have another; more men than women have kidney stones. Stones can be broken up ultrasonically or surgically removed.
