White blood cells in urine

Factors Causing White Blood Cells in Urine

Normally, there are very few white blood cells in urine; ideally, urine should not contain any blood components. Not only do the kidneys prevent the passage of blood into the urine; the mechanism of the urinary system, ordinarily, accords no way to cause such. The occurrence of white blood cells in urine, during urinalysis, could be an indication of an infection in the urinary tract, an infection in other systems of the human body that have spread out. The normal range should fall from 0-2/HPF (HPF means that the urine sample is analyzed through the high power field of a microscope); 5 or more per HPF indicates an infection; 10 or more per HPF indicates more serious conditions.

How do infections like urinary tract infection allow flushing of white blood cells in urine? It would be essential to touch upon the functions of white blood cells before examining specific disease conditions. White blood cells, which consist of only 1% of the total blood volume, aid very much in the functioning of the immune system. Granulocytes are white blood cells that engulf particles and small debris circulating in the blood. Lymphocytes produce antibodies that trigger immune responses to invading organisms within the human body. Monocytes, the largest among them, are capable of engulfing more foreign material than granulocytes can; they are also capable of leaving the vascular system and entering the tissues, where they become known as macrophages. When bacteria invade the human body, the white blood cells orchestrate an inflammatory response that fights off the bacteria.

The most common cause, therefore, is urinary tract infection (UTI). The urinary tract has an efficient mechanism of clearing out microorganisms through urination itself. The constant flushing keeps the urinary tract sterile. In urinary tract infection, somehow, bacteria invade the urinary tract, especially through the urethra, and cannot be cleared out because of bladder dysfunction, urinary obstruction, or urinary reflux. Infection thus leads to an immune response from white blood cells, thereby enabling them to intrude into the urinary tract. When that happens, the next time urine flows out, white blood cells in urine will be detectable. Bladder infections and kidney infections, which usually proceed from urinary tract infections, also contribute to that. A finding of infection or inflammation could be supported not only by the presence of white blood cells in urine, but also by the presence of many bacteria – bacteria not ordinarily found in the skin surrounding the urethra. (Determining which type of bacteria is the culprit leads to proper diagnosis of the underlying conditions.)

Systemic disorders (like systemic lupus erythrematosus), or more widespread infections (like sepsis), which trigger massive immune responses, could also lead to having white blood cells in urine. Swelling of the kidneys (nephritis) or renal failure also shuts down some filtration processes in the excretory system, thus allowing the presence of white blood cells in urine. Other causes include kidney or bladder stones, Kawasaki disease, renal tuberculosis, and tumors in the urinary tract.