Leukocytes are white blood cell that can be found in urine in cases of pyuria.
The urinary system consists of the kidneys, ureters, bladder and urethra. Normally only a few white blood cells are found in urine. However, certain conditions can cause significant increases in white blood cells in a urine sample. A microscopic or chemical test-strip urinalysis can determine whether there are leukocytes in a urine screening. Problems or abnormalities in any of these structures can cause leukocytes to be found in the urine.
Infection
Screening tests for white blood cells in urine typically detect the enzyme esterase in leukocyte cells. Lab Tests Online notes that the most common cause of leukocytes in urine is a bacterial urinary tract infection. This can be an infection in the kidneys, which is called pyelonephritis or in the bladder, which is called cystitis. According to the MayoClinic.com, risks of urinary tract infections increase with weakened immune systems, pregnancy, tampon use and prolonged urinary catheter use.
Inflammation
The presence of leukocytes in a urine sample is an important indication of inflammation in the kidneys, bladder and urinary tract. In some conditions, inflammation in the body can lead to very high counts of white blood cells, which can increase the concentration of the leukocyte breakdown product esterase in the blood.
Physical Damage
Some cases of leukocytes found in the urine are caused by physical damage to the urinary tract and related urinary organs, such as the bladder and kidneys. The Mayo Clinic explains that inflammation can occur when the tract or organs are damaged due to passing kidney stones and other causes. The white blood cells accumulate at these sites and are passed with the urine.
