According to MedlinePlus, urinalysis is the medical examination of urine involving evaluation of the urine's color and appearance, observing the urine under a microscope and chemical analysis using a test strip called a dipstick. The presence of unexpected substances in the urine causes markers on the dipstick to change color. One substance detected using the dipstick is white blood cells, also called WBCs or leukocytes. The term "pyuria" means the abnormal presence of WBCs in urine. Although pyuria typically indicates an infection in the bladder or kidneys, WBCs in urine occur for other reasons.
Contamination
The paper "The Measurement and Meaning of Pyuria," published in "Archives of Disease in Childhood," notes that for women, WBCs from the vagina frequently contaminate urine. The simple act of urinating can introduce WBCs comparable to numbers found in urinary tract infections. It is important that a women cleanse her genitals with the sterilized wipes provided and then take a urine sample in midstream--urinate a bit, stop, put the collection container in place, urinate again--to prevent contamination.
Interstitial Nephritis
Interstitial nephritis occurs when the spaces between the kidney tubules become inflamed or swollen. Inflammation harms the kidney's ability to filter waste, leading to the presence of WBCs in the urine. The AAFP article "Diagnosis and Management of Acute Interstitial Nephritis," reports that the causes of interstitial nephritis include allergic reactions to a medication, side effects from some antibiotics or antidiuretics and long-term use of painkillers such as acetaminophen, aspirin or ibuprofen. Symptoms include decreased urine production, rash, nausea, vomiting, drowsiness, confusion, swelling and weight gain from retaining fluid. Treatment focuses on the cause, and stopping the suspected medication typically leads to quick improvement.
Kidney Stones
According to "Renal & Urology News," kidney stones can cause WBCs to appear in the urine, with 67 percent of patients being men. Kidney stones vary in size and can be as small as a grain of sand. Often they pass through the body without requiring help, but occasionally they can block the urinary tract, causing extreme pain. MedlinePlus reports that symptoms of a kidney stone requiring a doctor's help include lower back or side pain, fever, chills, vomiting, burning during urination and urine that is cloudy, contains blood or smells unpleasant.
