Leukocytes (white blood cells) are a fundamental component of the body’s immune system, defending against infections and inflammation. Their presence in urine is called pyuria. Pyuria often signals an underlying health issue, such as an infection or inflammatory response within the urinary tract or adjacent organs. This article explores the connection between sexually transmitted infections (STIs) and leukocytes in urine, along with other potential causes and diagnosis.
What Are Leukocytes in Urine?
Leukocytes are immune cells that play a central role in the body’s defense mechanisms. Their presence in urine, or pyuria, indicates that the body is mounting an inflammatory response to combat an infection or irritation somewhere in the genitourinary system. While a small number of white blood cells in urine can be normal, an elevated count suggests a problem. A diagnosis of pyuria is often made when there are at least 10 white blood cells per cubic millimeter of urine or more than 3 white blood cells per high power field in unspun urine.
The detection of leukocytes in urine commonly occurs through several laboratory methods. A urinalysis is a standard test that involves examining a urine sample for various abnormalities. This typically includes a urine dipstick test, which uses a chemical strip that changes color if leukocyte esterase, an enzyme found in white blood cells, is present. Microscopic examination of urine sediment further allows for direct visualization and counting of white blood cells.
STDs Linked to Leukocytes in Urine
Several sexually transmitted infections can lead to the presence of leukocytes in urine, representing the body’s immune response to these pathogens. Chlamydia, caused by the bacterium Chlamydia trachomatis, is a common STI known to induce an inflammatory reaction in the genitourinary tract. This inflammation results in white blood cells migrating to the affected area and subsequently appearing in the urine.
Similarly, Gonorrhea, caused by Neisseria gonorrhoeae, frequently triggers a robust immune response that includes an influx of leukocytes. This bacterial infection can affect the urethra, cervix, or rectum, leading to inflammation and the shedding of white blood cells into the urine. Trichomoniasis, an STI caused by the parasite Trichomonas vaginalis, also commonly presents with pyuria. The parasitic infection irritates the urinary and genital tracts, prompting the immune system to send white blood cells to the site of infection. When leukocytes are found in urine without a detectable bacterial infection through standard cultures, a condition known as “sterile pyuria” may be present, which is often linked to STIs or viral infections that are difficult to culture.
Non-STD Causes of Leukocytes in Urine
Many conditions unrelated to sexual transmission can also lead to pyuria. Urinary Tract Infections (UTIs) are a frequent cause, occurring when bacteria enter and multiply within any part of the urinary system, such as the bladder (cystitis) or kidneys (pyelonephritis). The immune system dispatches white blood cells to fight these bacterial invaders, leading to their presence in urine.
Other non-STD causes include kidney stones, which can irritate the urinary tract lining and provoke an inflammatory response. Interstitial cystitis, a chronic bladder condition characterized by pain and pressure, can also result in pyuria due to ongoing inflammation. In men, prostatitis, or inflammation of the prostate gland, can cause leukocytes to appear in urine. For women, non-STD related vaginitis, such as bacterial vaginosis or yeast infections, can lead to vaginal discharge that contaminates a urine sample, resulting in a false positive for leukocytes. Certain medications or systemic inflammatory conditions, including autoimmune diseases, may also contribute to elevated leukocyte levels in urine.
Interpreting Test Results and Seeking Care
The presence of leukocytes in urine is an indicator of inflammation or infection, not a definitive diagnosis of a specific condition. Therefore, a positive leukocyte test result necessitates professional medical consultation to determine the underlying cause. A healthcare provider will typically begin by taking a detailed medical history and performing a physical examination to gather more information. This initial assessment helps guide further diagnostic steps.
Additional specific tests are often ordered to pinpoint the exact cause of pyuria. A urine culture can identify the specific type of bacteria, if any, responsible for an infection and determine its susceptibility to antibiotics. If an STI is suspected, specific tests like nucleic acid amplification tests (NAATs) may be performed to detect the genetic material of STI-causing organisms. Imaging studies, such as ultrasounds or CT scans, might be used to investigate structural issues like kidney stones or other abnormalities within the urinary tract. Proper diagnosis is important because treatment depends entirely on the identified cause, ranging from antibiotics for bacterial infections to other interventions for non-infectious conditions.