A common culprit for the presence of nitrites and leukocytes in urine is a urinary tract infection (UTI) that invades the kidneys and bladder. The detection of urinary leukocytes during urinalysis might also indicate serious medical conditions, such as systemic lupus erythematosus (SLE), prostate issues and urinary obstructions. Pregnant women might occasionally secrete trace amounts of leukocytes and protein in the urine without much concern.
Leukocytes are white blood cells that protect the body from infections and certain diseases. White blood cells in the urine are detected by measuring the amount of leukocyte esterase in the urine. Esterase is an enzyme that is produced by white blood cells, and it is the identifying factor in detecting leukocytes. Positive leukocyte esterase tests are usually indicators of an UTI.
Women are far more likely to experience UTIs than men. Common UTIs that cause urinary leukocytes in both genders are cystitis and an intestinal bacterium called Escherichia coli. Cystitis is a bladder infection; sometimes the term is referred to bladder inflammation caused by a bacterial infection. Pyelonephritis is a UTI that affects the kidneys and has the potential to become life-threatening if left untreated. These UTIs usually are treated with antibiotics until the infection is no longer present.
Some men might experience acute or chronic prostatitis, which is the inflammation of the prostate gland leading to difficulty urinating and pain. In both cases, leukocytes are found during urinalysis. Acute and chronic bacterial prostatitis is likely caused by any number of bacteria that cause a UTI or sexually transmitted disease (STD). The cause of chronic nonbacterial prostatitis is not entirely known, but some experts have speculated that an inflammatory condition might be to blame.
In the absence of an UTI, urinary leukocytes combined with protein and erythrocytes might indicate lupus nephritis which is a complication of SLE. Lupus nephritis is a chronic inflammatory disease of the kidneys that might damage the kidneys and eventually lead to kidney failure. A urinalysis and kidney biopsy is necessary to properly diagnose the condition. Treatment involves immunosuppressant drugs such as corticosteroids and dietary restrictions limiting the consumption of protein, potassium and sodium.
Other underlying causes of leukocytes that do not involve a UTI are urinary obstructions and pregnancy. Urinary obstructions can take the form of a tumor or kidney stones. In the case of kidney stones, the presence of urinary leukocytes indicates inflammation rather than infection. Trace amounts of leukocytes in pregnant women, in the absence of cystitis or other UTI conditions, might indicate contamination of vaginal secretion.