Changes in urine appearance, such as cloudiness or an unusual odor, often signal an internal issue. When the urine takes on a distinctly murky or milky appearance, it may indicate the presence of inflammatory cells. These cells are a sign that the immune system is actively fighting off an irritant or an infection within the urinary tract.
The Medical Term for Pus in the Urine
The specific medical term for the presence of pus, or white blood cells, in the urine is pyuria. This condition is formally defined by the detection of an abnormally high number of leukocytes when the urine is examined in a laboratory setting. Pyuria is typically diagnosed when the count exceeds 10 white blood cells per cubic millimeter of uncentrifuged urine, or 5 to 6 per high-power field in a centrifuged sample.
Sometimes, the amount of pus is so significant that it causes the urine to appear visibly cloudy or opaque, a state referred to as gross pyuria. More commonly, the presence of these immune cells is not obvious to the naked eye and is only discovered during laboratory testing, which is known as microscopic pyuria.
Identifying the Root Causes of Pyuria
Pyuria is a symptom, not a diagnosis, and its presence points toward an underlying inflammatory process that requires identification. The most common source of white blood cells in the urine is an active bacterial infection somewhere along the urinary tract. These infections, known as Urinary Tract Infections (UTIs), cause immune cells to rush to the site of invasion to combat the invading microorganisms. If the infection has traveled upward from the bladder to the kidneys, a condition called pyelonephritis, the resulting pyuria can be much more pronounced and is usually accompanied by fever and flank pain.
Certain sexually transmitted infections (STIs), such as gonorrhea or chlamydia, can also cause inflammation in the urethra that leads to the release of white blood cells into the urine. In these cases, the inflammation is localized to the lower urinary tract and may present with burning during urination.
A more complex situation arises with “sterile pyuria,” where the white blood cell count is elevated, but standard bacterial cultures come back negative. This result indicates that the inflammation is not caused by typical bacterial pathogens that grow in standard lab tests.
Other non-infectious causes include interstitial nephritis, which is inflammation of the kidney’s tubules and surrounding structures, often due to a reaction to certain medications. Systemic inflammatory conditions, such as Kawasaki disease or tuberculosis, may also present with sterile pyuria, requiring further investigation.
How Doctors Confirm Pyuria
Confirming the presence of pus in the urine begins with a simple, non-invasive procedure called a urinalysis. This test involves two main components: a dipstick test and a microscopic examination of the urine sample. The dipstick is a chemically treated strip that can quickly detect the presence of leukocyte esterase, an enzyme released by white blood cells, providing a rapid preliminary indicator of pyuria.
The microscopic examination then provides a definitive count of the white blood cells present in a specific volume of urine. During this step, the technician also looks for other signs of infection, such as bacteria or red blood cells, which helps the physician narrow down the cause. If the urinalysis suggests an infection, the next step is usually a urine culture. The urine culture involves placing a sample on a growth medium to identify the specific species causing the infection. This process also includes antibiotic sensitivity testing, which determines which antibiotics will be most effective against the identified microorganism.
Treating the Underlying Condition
Since pyuria is a manifestation of an underlying health issue, successful resolution depends entirely on treating the root cause identified through testing. When diagnostic tests confirm a bacterial infection, such as a UTI or pyelonephritis, the standard treatment involves a course of appropriate antibiotics. The specific antibiotic chosen is guided by the sensitivity results from the urine culture, ensuring the medication is potent against the identified pathogen.
It is important for patients to take the entire prescribed course of antibiotics, even if symptoms begin to improve quickly. Stopping the medication prematurely can lead to a recurrence of the infection and may contribute to the development of antibiotic-resistant bacteria, making future infections harder to treat. The white blood cell count in the urine typically begins to normalize shortly after antibiotic therapy is initiated.
For cases of sterile pyuria, where the cause is non-infectious, the treatment approach shifts away from antimicrobial agents. If the pyuria is caused by the irritation of a kidney stone, management may involve pain relief, increased fluid intake, or procedures to break up or remove larger stones. When drug-induced interstitial nephritis is the cause, the physician will typically discontinue the offending medication and may prescribe corticosteroids to reduce kidney inflammation. Addressing systemic inflammatory conditions requires treating the primary disease with targeted medications, which in turn resolves the secondary symptom of pyuria.